Estimating the time a project will take is essential to creating realistic deadlines, establishing an appropriate budget and team schedule, and setting expectations for employees and stakeholders. This guide covers the estimated time to complete (ETC) projection and the best ways to estimate timing for project management.

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Knowing how long a project will take allows you to create realistic deadlines, manage resources, establish a budget, schedule staff, and set expectations for employees and stakeholders alike.

Without proper planning, projects that should have taken a few weeks can end up dragging on for months. This can cause you to go over budget, result in increased labor costs, and leave your customers unhappy.

Project managers use estimated time to complete (ETC) projections to estimate time effectively. In this guide, we go over exactly what ETC is, how to properly estimate timing, and more.

What is Estimated Time to Complete?

A project’s ETC is an evaluation of the amount of time required to complete all its tasks. It helps you plan out the tasks you need to complete and ensures everyone knows how long they have to work. ETC is more accurate than simply guessing and gives you more confidence when it comes to setting a budget, allocating resources, and scheduling employees.

ETC should be calculated as early as possible in the project lifecycle to ensure it’s as accurate as it can be.

The Importance of Proper Time Estimates

Firstly, setting proper time estimates helps your team avoid delays so you can deliver completed projects on time. You need to be able to meet deadlines consistently in order to build trust with your customers so they’ll continue to request your services. ETC can help your team manage their time efficiently so that all projects meet or exceed client expectations.

Accurate time estimations also help you budget appropriately and ensure you have the right employees available to work on certain tasks as projects move forward.

Additionally, ETC can help you create detailed schedules. These schedules can include task deadlines based on your projections, as well as information on what each person is responsible for doing. Your employees will be more productive, and you’ll be able to manage them more effectively.

Without an accurate ETC projection, you risk budgeting incorrectly, missing deadlines, and overworking your employees in an effort to catch up. Delivering projects late or over budget can disappoint your clients and damage your reputation. In some cases, a poor time estimate can make it impossible to complete a project altogether.

Tips for Estimating Time Correctly

Improper time estimation can be costly and dangerous, but here’s what you can do to estimate time correctly.

Review data from past projects

Looking over data from past projects can help fine-tune your time estimates. You can review past project timelines, notes, files, invoices, and anything else that might help you understand how long each project took to complete. Then, you can use that information to guide your current ETC projections.

Make sure you’re reviewing similar projects to ensure the information is relevant and helpful. Also, note any new technology or processes that you’ve implemented that may make your current project easier to complete.

For example, if you find that a similar past project took 150 hours to complete, you might estimate that your current project will take 150 hours as well. However, you may note that your business has brand-new software that cuts scheduling time down from 5 hours per week to just 1. You can then adjust your time estimate accordingly.

Break projects down into individual tasks and create to-do lists

Without full knowledge of all tasks and requirements related to a project, you’ll find it challenging to estimate time to complete.

To make this easier, you can break projects down into smaller tasks and create lists of what needs to be done each day. When you have your to-do lists laid out, estimate the time it will take to complete each task. For example:

Monday, June 1

9 am meeting with client – 1.5 hours
Write project proposal – 4 hours

Tuesday, June 2

Proposal presentation – 2 hours

Wednesday, June 3

Create budget – 1.5 hours
Budget approval meeting – 1 hour

Thursday, June 4

Email client with approved budget – 10 minutes

Friday, June 5

Work site inspection – 6 hours
5 pm dinner with clients – 2 hours

In this example, the first week of your project will take 18 hours and 10 minutes to complete. Continue to plan out project tasks for each day, then add up the time to get an ETC projection.

Use three-point estimating

This method involves making three estimates on project time: the best-case scenario, the worst-case scenario, and the most likely scenario.

The best-case scenario estimate is if everything goes according to plan with zero issues, and the worst-case estimate is if everything that could go wrong does go wrong. The most likely estimate is one that accounts for only a few hiccups along the way.

Three-point estimating is often the safest way to estimate timing, as it helps ensure you’re prepared no matter how a project goes. That being said, it does take a lot of effort. Many project managers will end up using the average of all three scenarios to arrive at an actual estimate.

Use the Time Estimation Formula

Three-point estimating goes hand in hand with the Time Estimation Formula. This takes your best-case scenario (A), most-likely scenario (B), and worst-case scenario (C) in order to give you an estimate of when you’re most likely to finish a project (E).

The formula is E = (A+4B+C)/6.

Let’s say your best-case scenario time for a project is 150 days, your most likely is 175 days, and your worst-case is 225 days.

E =150 + (4 • 175) + 2556

E = 179.16

We can see from the formula that the project is likely to finish in just over 179 days.

You can also use the standard deviation formula of SD = (C-A)/6 to get a larger range for how long your project is likely to take.

Let’s use the standard deviation formula in the above example.

SD = 226 – 1506

SD = 12.5

A standard deviation of 12.5 means the project will likely fall somewhere between 12.5 days longer and 12.5 days shorter than the 179 days that the time estimation formula states. As a result, the project is most likely to take you between 166.5 and 191.5 days to complete.

Bottom-up estimating

This method involves analyzing tasks individually and going over how much time each is likely to take. Then, you simply add up the time of the individual tasks, and you’re left with the total estimate for the entire project.

For example, imagine you have one task that will take 1 week, one that will take 5 weeks, and one that will take 2 weeks. Your total time estimate for the project will be 8 weeks.

This can be a very accurate way to estimate hours for projects, as it forces you to look at each specific task first and then the project as a whole.

Top-down estimating

With this method, you figure out how much time you have to work on a project, then split that time up among the project’s tasks.

You might consider using historical data to get a sense of how long the entire project should take and make your estimates from there. Or you might estimate time to complete based on a client’s specifications.

For instance, you might estimate that the project will take 12 weeks to complete, based on your experience with past projects. You can divide that time up into a certain number of days or weeks for each project task. One task might take 3 days, while another might take 2 weeks.

Overall, top-down estimating can be a quicker and simpler approach, as you focus more on the project as a whole and not each task in detail.

Use parametric estimating

This method involves figuring out the time required for a single task and then multiplying that time by the number of similar tasks involved in the project. Many tasks in a project are similar, and this method allows you to make accurate estimates without having to analyze each one.

For example, say a similar task in the past took you 10 hours and you need to complete 12 of these tasks for your current project. Therefore, a good ETC would be 120 hours.

Since parametric estimating requires you to group similar tasks together to estimate project time, some variation can occur—especially if the tasks aren’t as similar as you originally thought. Still, this method can be helpful as long as you know the tasks and what they require.

Use comparative estimating

Comparative estimating (also known as analogous estimating) is when you determine how long similar past projects took to complete, and then apply these insights to your current project.

For instance, you can estimate that a current project will take 4 months to complete if you and your team spent 4 months on a similar project in the past.

You can estimate time quickly and easily using this method, but accuracy can suffer if your current project and the past project you’re referring to have different requirements.

For example, a past project may have required 1 work site inspection, while your current project needs 2. That would add extra time to complete your project, so you would need to factor that in to your total time estimate.

Track time spent on tasks and projects

Tracking time tells you exactly how long specific tasks and projects take to complete, and can show you what tasks you and your team spend the most time on.

It’s as easy as starting a timer when a task starts, stopping it when it’s done, and recording the amount of time that was spent. You can also use a digital app, like Connecteam, with a time clock that automatically records time down to the second.

By tracking time, you can easily adjust your current estimates based on the actual time it takes to complete tasks. For example, say you estimated that a certain task would take 12 hours to complete. But you’ve been tracking time and see that it’s actually taken 15 hours. You can

Similarly, tracking time ensures that your team isn’t falling behind on tasks. Let’s say that you estimated 40 hours for one project task, but your team has recorded 20 already and the task isn’t halfway done yet. This could signal that your team needs to work more quickly. You can speak with them and see how to make that happen.

Additionally, tracking time provides you with accurate time records that you can review when making future time estimates.

Account for wasted time

Keep an eye out for the time ‌you spend on other things while working on a project. You’re bound to chat with your team members, check emails, grab something to eat or drink, or otherwise get distracted.

Avoiding time waste altogether is simply unrealistic, so it’s better to work it into your total estimate. You can do this by creating a list of common activities you do each day while working on a project. Then, estimate the amount of time each takes.

For example:

Chatting with coworkers – 30 minutes
Two smoke breaks – 30 minutes
Grabbing a cup of coffee – 15 minutes
Checking emails – 25 minutes
Grabbing a snack near the job site or office – 20 minutes
Lunch break – 30 minutes

That works out to 150 minutes, or 2.5 hours, of time each day not spent actively working on a project. This means that you work productively for 5.5 hours each day, if you work 8-hour days. Knowing this can help you create more precise time estimates.

Add in extra time for emergencies

When creating project plans and figuring out timing, it’s important to schedule additional time in case you end up needing it. Plans with tight turnaround times that don’t allow for flexibility can fall apart when just a single issue arises.

For example, factor in extra time to address challenges like labor shortages, equipment failures, power outages, inclement weather, and even certain resources being unavailable.

Involve your team and seek expert opinions

Consulting with your employees can help ensure that your estimates are reasonable and accurately reflect the time it takes to complete projects. To get their thoughts, you can hold meetings, have one-on-one calls or discussions, or send out polls or surveys.

For instance, you may estimate that a project will take 200 total hours to complete, but your team might feel that 250 hours is a more realistic estimate.

Involving your team in time estimates makes employees feel valued and capable. This then makes them more engaged, which improves employee satisfaction. Additionally, they’ll be more motivated to work hard and stick to a project’s timeline if they’ve helped to create it.

Also, don’t hesitate to reach out to experts or specialists who have worked on similar projects. People with specialized experience and knowledge can give you a better sense of how long a project should take.

Track progress and review your timeline after project completion

You should make an effort to track progress throughout each project. This way, you can quickly adjust your time estimate if any issues come up. The right or even free task management tools—such as checklists, on-to-go task assignment, and task notifications sent straight to employees’ devices—can make tracking easy.

Plus, tracking progress lets you compare how projects are actually going against your estimates. This helps make future time projections more accurate.

Finally, when a project is done, review its timeline in detail. Look at each task and ask yourself the following questions:

How long did it take?
How much money was spent?
Were the goals/objectives met?
Who worked on the task and how did they perform?
How satisfied was the team and/or client with the task?

This can give you a clear look at the actual project duration and overall success compared to your estimate. You can easily identify any differences between the estimate and the outcome and make decisions on how to address them in your next project.

Conclusion

Without knowing how to correctly estimate time, you could end up with failed projects. Your projects can run over budget, and you can miss important deadlines. Poor time estimating ends up wasting a ton of time and money, and leaves customers less than thrilled.

No matter what kind of projects your business takes on, using estimated time to complete (ETC) projections can help you better predict how long it will take to complete projects. Your employees will have a better understanding of what they need to do—and by when—and you’ll maintain a strong reputation by consistently delivering projects on time.

A Three-Point Estimating Technique: PERT

The Program Evaluation and Review Technique (PERT) is used to find the estimated time for activities to be completed when there are many unknown factors. With origins in the US Navy, PERT has been in use for over 60 years, speaking to the value it brings to project managers. The Project Management Institute (PMI)’s Project Management Professional (PMP®) certification exam may include questions referencing PERT, which is a three-point estimating technique used by project managers across industries to estimate activity duration or cost.

On this page:

PMP® Exam Formula Cheat Sheet

Learn how to successfully use project management formulas after reading this cheat sheet.

The Three Points of Three-Point Estimating (PERT)

The PMI’s A Guide to Project Management Body of Knowledge (PMBOK® Guide) – Sixth Edition, provides this definition for the three-point estimating technique:

Three-Point Estimating

A technique used to estimate cost or duration by applying an average or weighted average of optimistic, pessimistic, and most likely estimates when there is uncertainty with the individual activity estimates. See also analogous estimating, bottom-up estimating, parametric estimating, and program evaluation and review technique (PERT). – Source pmi.org/pmbok-guide-standards/lexicon

Note within the PMBOK® Guide’s definition, there are multiple types of three-point estimating tools. The Program Evaluation and Review Technique (PERT), informally known as “PERT PMP,” is one type.

Consider this example from a common situation outside of a business environment. Three estimates are received for painting a house exterior. Calculating the average of the three cost estimates of the same effort provides insight into approximately what the final cost should be. Also, finding the average of the three expected durations of the work effort will provide insight into how long the project should take. Analysis using a three-point estimate provides insight into the expected cost and duration for the planned work.

Understanding PERT for Projects: Three-Point Estimating PMP

PERT has been used across the globe, in many industries, and for decades. PERT has become the most used and popular method of choice among project managers due to its reliability and accuracy.

The PMBOK® Guide online lexicon provides this definition for PERT:

Program Evaluation and Review Technique (PERT)

A technique used to estimate project duration through a weighted average of optimistic, pessimistic, and most likely activity durations when there is uncertainty with the individual activity estimates. See also analogous estimating, bottom-up estimating, parametric estimating, and three-point estimating. – Source: pmi.org/pmbok-guide-standards/lexicon

Note the PMBOK® Guide definition is not “PERT PMP,” nor “PERT Analysis PMP,” as those are not the formal names for the technique. As for when in a project to use PERT analysis to determine a schedule or cost estimate, it is best during planning and implementation. Key points about PERT include:

PERT is used to estimate project duration or cost.
PERT is a “weighted” average estimate technique.
PERT is best used for planning to ensure accurate scope.
PERT formula is an approximation of the Beta Distribution equation.
PERT is determined using three points: Optimistic (O), Most Likely (M), and Pessimistic (P).
PERT combines probability theory and statistics to derive a formula for the average activity from the three-point estimates.
PERT estimate formula is: (O + 4M +P) / 6

When studying PERT as part of preparing to take the PMP® exam, it is important to know it is one type of three-point estimating, what it can be used to estimate (duration or cost), and when in the project to use it.

Optimistic Estimate

The “Optimistic estimate” is one value within the PERT formula and is represented as “O.”

Optimistic Estimate (O)

Estimate for all favorable conditions with no risks or changes

The Optimistic Estimate is the “best-case” and thus shortest duration, or lowest cost, to complete the work.

Pessimistic Estimate

The “Pessimistic estimate” is used in the PERT formula and is represented as “P.”

Pessimistic Estimate (P)

Estimate for all unfavorable conditions with all negative risks occurring and no mitigation of negative risks

It is the opposite of the Optimistic estimate in concept. The Pessimistic Estimate is the “worst-case” and thus longest duration, or highest cost, to complete the work.

Most Likely Estimate

The third value in the PERT formula is the Most Likely estimate and is represented as “M.”

Most Likely Estimate (M)

Estimate for both favorable and unfavorable conditions, with some risks occurring.

The name is accurate in the estimate is based on changes, but ones that have been planned for and can be mitigated. The Most Likely estimate captures the highest likelihood of completing the work in the given duration or cost.

Program Analysis Review Technique (PERT) Formula

The three points O, P, and M are used in the Program Analysis Review Technique (PERT) formula. It uses a weighted average (not a simple average) to determine the mean of the three estimated values.

Three-Point Estimating, PERT Formula PMP

The M value, Most Likely, is given 4 weights as the PERT formula is based on probability theory and statistics, specifically Beta Distribution. More weight is given to the most likely (after all, it is the most likely). If plotted against a chart, this beta distribution will result in a more uniform, bell-shaped curve, called a normal distribution.

PERT Example

Within a large city, some factors influence how long it takes to drive from home to the office. The weather, the time of day, and any vehicle accidents on the road can impact the duration to get from home to the office on those roads.

Most Likely (M)	60 minutes	clear weather, clear roads, normal volume of drivers on some of the roads
Optimistic (O)	30 minutes	clear weather, clear roads, no other drivers on any road
Pessimistic (P)	120 minutes	thunderstorm with rain, road blocked from multiple vehicle accidents, the highest volume of drivers

The weighted average of the three estimates is used in the PERT formula:

PERT = (30 + [4 x 60] + 120) / 6
PERT = 390 / 6
PERT = 65 minutes

Staying with this example, consider if asked “how long does it take you to drive to work?”. Have you ever replied with “well, if it is a weekday at 8 am, it usually takes me 30 minutes longer than if it is a sunny weekend afternoon.” You are giving different estimates reflecting different situations for the same activity. Using PERT analysis, the estimates go from “guesses” to mathematically verified estimates.

Pros and Cons of Three-Point Estimating using PERT

Program Evaluation Review Technique (PERT) is a project management planning tool used to calculate the amount of time it will take to realistically finish a project. PERT charts are used to plan tasks within a project — making it easier to schedule and coordinate team members. The Small Business Chronicle article What Are the Pros & Cons of PERT Charts? provides a breakdown of the advantages and disadvantages of the tool, summarized below:

pros and cons of three-point estimating pmp

PERT and the PMP® Certification Exam

PERT analysis PMP exam questions may include the need to calculate estimates using the formula or interpretation of graphed or charted data. Elements within a question can indicate if Beta Distribution using PERT is the best tool, e.g., experts are available, and the project is similar to other projects. Overall, in studying PERT PMP exam questions, be prepared to use the formula, do a basic analysis of a PERT estimate, and know when PERT is most effectively used.

Example PERT PMP® Exam Questions

Question	A	B	C	D
You are a project manager working on a life sciences project. You are reviewing previous projects that are similar to get some estimating ideas. Additionally, you have met with vendors to get a sense of how long some activities may take if you decide to outsource. You are working on preparing your activity duration estimates and are meeting with the relevant experts to determine how long each activity should take. You know you will use PERT analysis to derive your figures. What indicators should you be gathering so that you can utilize PERT?	Triangular estimates	Pessimistic, Optimistic, and Most likely estimates	Best and Worst case estimations	Standard deviation
You are developing your project schedule and have decided to use the PERT method to determine project duration. The estimates you’ve gathered so far include the following: Most likely is 200 hours, optimistic is 180 hours, and pessimistic is 220 hours. Which of the following is the correct PERT estimate (beta distribution)?	190	226	200	210

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Conclusion – Three Point Estimating

The Program Analysis Review Technique, or as some refer to it, the “PERT Analysis PMP,” has remained a project manager mainstay because of the power to provide duration and cost estimates in situations with limited data. The time and resources needed to conduct a PERT analysis in the planning stages can be prohibitive but balanced out by the benefit of accurate estimates for the minimum needed to complete a project. Leveraging the three-point estimate technique, the PERT tool is a proven and practical estimating tool for communicating the activity needs and work of a project.

Tuesday, 6 August 2024

How to estimate time for a project