Schedule Variance: What It Is and How to Calculate It

Imagine this — you’re working on a software development project. A team member comes up to you, saying that he didn’t receive a file that was supposed to be delivered yesterday. 

You check with the person who was tasked to deliver the file — it turns out they can’t do their share without another file they haven’t received from another team member.

Going down the chain like this, you figure out a domino effect has been happening right under your nose. Every individual delay was short, but together they added up massively. 

How do you stop these kinds of issues from happening?

You can do so by using schedule variance — a variable that can quickly show if and how much your project is behind schedule, and how much harder team members need to work to catch up.

In this guide, we will take a look at:

• What schedule variance is,
• Different ways to calculate it,
• Examples of schedule variance calculations,
• The causes of project delays, and
• Tips for making schedule variance calculations.

What is schedule variance?

The idea behind schedule variance (SV) is simple — if you’ve finished less work than you thought you would, you’re behind schedule.

Or, as The Standard for Earned Value Management puts it, “Schedule variance (SV) is a measure that reflects the difference between the amount of work planned to be accomplished and the amount of work actually accomplished at the present time.”

Calculating SV also tells you: 

• How to measure the work you’ve finished, 
• How far behind schedule you are, and
• How much harder you should work to catch up.

Schedule variance is useful because it shows you both whether you are on schedule and how to adjust your work accordingly.

How to calculate schedule variance

There are multiple ways to calculate schedule variance. Each calculation gives us a slightly different benefit for analyzing the next step in managing our project. 

Keep in mind that schedule variance — as well as all associated variables — are represented in monetary terms. This allows us to work with whole, more precise numbers.

We’ve listed 4 calculations related to schedule variance:

• Schedule variance (SV),
• Schedule variance percentage (SV%),
• The schedule performance index (SPI), and
• To complete schedule performance index (TSPI).

However, it’s good to note that the first 2 represent schedule variance calculations, while the last two are project KPIs that are closely related to schedule variance.

But, before we begin explaining each calculation, there are some variables we should get acquainted with:

• BAC — BAC stands for budget at completion. As per the Standard Earned Value Management, it represents “the sum of all budgets established for the work to be performed. It is the approved budget to complete the entire work scope.”
• EV — EV stands for earned value. This is the realistic measurement of the amount of work completed at a certain time. Since it is traditionally calculated in monetary units, you can also say it is the budget allocated for the work that’s been completed until a specific point in time. Earned value can be calculated as: 

EV = (% of actual work completed) * BAC

• PV — PV stands for planned value. This is the expected amount of work at a certain point in time. It is the value of the expected work to be completed till the analyzed point in time. Planned value can be calculated as:

PV = (% of expected completed work) * BAC

Calculation #1: Schedule variance

The first method is the simplest one — it involves simple subtraction. It translates the following sentence into mathematical terms: 

Is the work completed so far in my project more or less than what I expected?

SV is, therefore, calculated by subtracting planned value from earned value. This is what the schedule variance formula looks like:

SV = EV — PV

There are 3 different results of this calculation: 

• If SV is less than 0 — you are behind schedule. This means you’ll have to work harder in the future to catch up.
• If SV is exactly 0 — you are exactly on schedule. 
• If SV is more than 0 — you are ahead of schedule. This means you have more leeway in how you manage your time for the remainder of the project.

Schedule variance serves to show whether or not you are on schedule. But, how much ahead or behind schedule are you, in reality?

It’s easy to presume that the bigger the number, the more ahead or behind schedule you are. And while that is logical, it’s not necessarily true.

For example, if you’re $400 behind schedule, but your project budget is $500,000 — there is not much need to worry. But, if your total budget is closer to $5,000, or even worse, $500, there would be plenty more reasons to worry.

So, schedule variance must be observed relative to the BAC.  

Calculation #2: Schedule variance percentage

The schedule variance percentage shows how the calculated SV relates to the planned value. It serves to indicate how much work has been or still needs to be completed.

The formula for schedule variance percentage is: 

SV% = SV / PV

Here, the variations to pay attention to stay the same: 

• If SV% is less than 0 — you are behind schedule.
• If SV% is exactly 0 — you are exactly on schedule.
• If SV% is above 0 — you are ahead of schedule. 

The benefit that SV% gives is that it tells you how much harder you need to work relative to the work you expected to have finished up until that point.

For example, if your SV% is -20%, you will need to complete a fifth of the PV just to catch up to your schedule. 

But, if it is 20%, you have a fifth of the PV less to deal with going forward, giving yourself that much space to relax.

Calculation #3: Schedule performance index (SPI)

SPI shows the percentage of work completed relative to the work expected to be finished at that time. 

The formula for calculating SPI is as follows: 

SPI = EV / PV

Again, we can use this formula to conclude if we’re ahead or behind schedule:

• If SPI is less than 1 — you are behind schedule.
• If SPI is equal to 1 — you are exactly on schedule.
• If SPI is more than 1 — you are ahead of schedule.

Furthermore, SPI determines how much work is done per unit of expected work in fractions. For example, if the SPI is 0.6, that means that for every unit of work expected, 0.6 units of actual work were completed.

If the SPI is 2, that means you’ve completed double the work you expected.

Calculation #4: To complete schedule performance index (TSPI) 

TSPI can be described as the polar opposite of SPI. 

Where SPI shows how much work was completed relative to the work expected, TSPI shows how much work is left to complete relative to the expected remaining workload at that stage of the project.

Because of this, the formula for TSPI is calculated using budget at completion:

TSPI = (BAC — EV) / (BAC — PV)

So, TSPI values mean the opposite of SPI values:

• If TSPI is more than 1 — you are behind schedule.
• IF TSPI is exactly 1 — you are exactly on schedule.
• If TSPI is less than 1 — you are ahead of schedule.

TSPI can also show how many units of work need to be completed per unit of work expected to stay on schedule. For example, if your TSPI is 0.6, you only need to complete a bit more than half the work per unit of work expected.

But, if your TSPI is 2, that means you’ll have to work twice as hard going forward to complete double the amount of work expected.

3 Examples of schedule variance

Formulas, by themselves, can be difficult to wrap your head around, so what do SV calculations look like in practice?

Let’s take a look at some examples of schedule variance and what the results tell us about the projects.

Example #1: Negative schedule variance

Let’s say you’re planning a nonprofit event.

You check your team’s progress, and they’ve completed 50% of the work for the project. You expected to complete $140,000 worth of work so far, and your total budget is $250,000.

Firstly, since we know our EV in percentages, we’d have to turn that into monetary values:

EV = (% of actual work completed) * BAC = 50% * $250,000

EV = $125,000

Now that we know our EV, we can easily calculate schedule variance:

SV = EV — PV = $125,000 — $140,000 = -$15,000

This means you are $15,000 behind schedule. If we look at our other indicators:

SV% = SV / PV = -$15,000 / $140,000 = -10.7%

So, SV% would be -10.7%, meaning you’d have to complete around a tenth of the work more going forward to stay on schedule. Looking at performance indicators:

SPI = EV / PV = $125,000 / $140,000 = 0.89

TSPI = (BAC — EV) / (BAC — PV) = ($250,000 — $125,000) / ($250,000 — $140,000)

TSPI = $125,000 / $110,000 = 1.09

SPI would be 0.89, which means that you’ve completed around a tenth less work than you expected to. TSPI would be 1.09, which confirms that around a tenth of the work needs to be completed to get back on track.

As we can see, all of these indicators show similar results, in slightly different ways. So, going forward, we’ll calculate only SV and SV% in our examples.

Example #2: Schedule variance of 0

This time, we’ll do something similar by calculating SV in an example of corporate event planning.

You’re making good progress, and you spent $24,000 of your budget. You expected to complete 80% of the work so far. Your BAC equals $30,000.

Using these metrics, we need to first determine our PV:

PV = (% of expected completed work) * BAC = 80% * $30,000 = $24,000

Now, we can already see that our PV equals EV, which will result in:

SV = EV — PV = $24,000 — $24,000 = $0

Since SV is 0, SV% is also 0, and you can determine that you’ve completed exactly the amount of work you expected to complete at this point in the project. 

Meaning, you don’t have to work harder since you’re on schedule, just make sure to stay on tempo.

Example #3: Positive schedule variance

And finally, let’s suppose you are working on a game development project. 

Say this game is a AAA release, so your budget stands at $70 million. You’ve completed 37% of the work, while you expected to complete 35%. Let’s get rid of those percentages first:

EV = 37% * $70,000,000 = (37 * $70,000,000) / 100 = $25,900,000

PV = 35% * $70,000,000 = (35 * $70,000,000) / 100 = $24,500,000

This puts our EV at $25.9 million and our PV at $24.5 million. Therefore, the schedule variance is:

SV = EV — PV = $25,900,000 — $24,500,000 = $1,400,000

We are a whopping $1.4 million ahead of schedule! However, this is why we mentioned that you should always view the schedule variance relative to your project budget. 

Our SV% shows us the following:

SV% = SV / PV = $1,400,000 / $24,500,000 = 0.057 = 5.7%

This means we are only 5.7% ahead of schedule. So, while we can give ourselves a bit of breathing room, we should be careful with how we view schedule variance.

The benefits of making schedule variance calculations

SV allows you, as a project manager, to be “in the know” about your project. This is beneficial in its own right, but we’ve listed some of the more important benefits of SV, such as:

• It provides project performance insight — as the most obvious benefit, schedule variance gives you direct and accurate insight into the real-time performance of your project. It allows you to adjust your expectations based on whether or not you are behind schedule.
• It points out delay issues — delays are not always easy to notice until you run the numbers. While it can only tell you when a delay is already underway, SV can help you prevent it from escalating. You can stop the cause of the delay as soon as you notice it and calculate how much harder your team has to work to make up for the delay. This allows you to get back on track with your project.
• It improves transparency — it’s good to stay transparent with your project stakeholders. Keeping everyone who influences the project updated on its performance can both prevent confusion and let everyone know if additional effort is needed.
• It gives valuable insight for future decisions — pointing out that an issue exists brings your attention to it. We will touch on this benefit later on, but SV helps you determine if there are issues in your project. By identifying these issues and finding solutions to avoid them in the future, you improve your project management skills.

Why isn’t schedule variance expressed in time units?

It can still feel a bit weird to say we’re $2,000 behind schedule. So, why don’t we calculate schedule variance in time measurements?

It’s certainly not impossible. However, this version of SV is heavily underused as it’s much more complicated to determine.

As per The Standard Earned Value Management, “Schedule variance can also be measured in the time (X) axis by considering the difference between the time already spent with the amount of work accomplished, and the time (according to the project baseline) that was expected to be spent to accomplish the same amount of work (but not necessarily that same work).”

That whole sentence boils down to another formula: 

SV(t) = ES — AT

ES (earned schedule) is the amount of time allocated for a certain amount of work. 

AT (actual time) is the amount of time it actually took to complete that amount of work.

However, time calculations can get fickle, and there are no direct formulas for calculating either ES or AT. 

So, it’s possible to calculate SV as a measurement of time. It’s just generally not done as it gives the same information after a more complicated process.

The best way to track how much time is expended on your project is to track specific tasks. For example, the project management tool Plaky has easy integration with Clockify — the world’s leading time-tracking app — to help you seamlessly track the time your tasks take.

What causes negative schedule variance & how to avoid it

There are plenty of reasons why negative schedule variances might appear in your project. It is highly likely that over the course of your project, you’ll encounter negative SV at least at one point. Sometimes, it even happens because of factors you can’t influence. 

The main causes of negative SV are:

• Incorrect planning
• Work pattern changes
• Workspace changes
• Lack of project resources 
• Lack of communication

Cause #1: Incorrect planning

An easy-to-guess but frequent cause of negative SV is incorrect planning. 

Not determining your planned value correctly, undershooting your budget, or failing to determine the right order of operations can all lead to devastating effects on your schedule variance. 

It’s easy to overshoot or undershoot project deadlines as a novice project manager.

Cause #2: Work pattern changes

Work pattern changes include forces that influence the way your schedule will be executed. 

We can easily predict some, like vacation days or holidays. However, some are more unpredictable — for example, sick days or workplace conflicts can take away from your schedule. 

Another factor could be delivery delays, which may halt your team’s workflow.

Cause #3: Workspace changes

This includes any changes you make to your workspace during the course of your project. The time it takes for your team to get acquainted with a new workspace will influence your schedule variance. 

For example, if you decide to start using a new communication tool or switch offices, you can presume that negative schedule variance will occur.

Cause #4: Lack of project resources

You must be aware of your project resources, as they are essential to the success of any project. Estimating them incorrectly can easily lead to negative SV. 

It’s easy to imagine how a smaller-than-needed team can lead to negative SV. But, this goes for any lack of resources — you can have the best product in the world, but if you don’t save finances for marketing, it might not take off. 

Cause #5: Lack of communication 

Communication is key to any project’s success. 

Inversely, a lack of communication leads to project failure. If your team cannot communicate with you whenever they are stuck on an issue, it cannot be fixed, causing delays. If you don’t set clear expectations, your team will be too lenient with their time — again, causing negative SV.

4 Tips for schedule variance calculations

With plenty of moving parts and a whole project in front of you — keeping track of your schedule can be a mind-boggling task.

To help you, we’ve listed 4 tips that can make your SV analysis less of a headache.

Tip#1: Frequently calculate schedule variance

While we’ve thoroughly preached the importance of tracking your schedule variance, we don’t expect you to calculate it daily.

But, it is necessary to make frequent SV calculations. You can do this at any stage, depending on your project scope (with smaller projects, it might be more often). 

You should also calculate SV whenever you need to communicate with stakeholders. This way, you’ll ensure transparency and keep your stakeholders informed with real-time information on the progress of your project.

But calculating schedule variance often can be time-consuming in its own right. While the calculation itself is pretty straightforward, the most time-consuming part of this can be gathering information. The logical solution — keep all of your project information in one place.

A great way to do that is to use project management software, where it’s easy to track your project’s progress. Let’s take a look at a practical example, using a free project management platform like Plaky.

Plaky allows you to have all the information about your project and tasks in one place, allowing you to easily calculate your SV based on the data whenever you need.

You can also mark all the tasks that are behind schedule so that you can see where you need more work.

Tip #2: Pay attention to symptoms, causes, and recommended actions

To properly deal with negative schedule variance, you must make yourself familiar with its:

• Symptoms — these are the first signs that a negative variance may appear. For example, if you notice the beginning of a workplace conflict, you want to resolve it as quickly as possible. You might also notice an issue in your project timeline. If unresolved, those issues can cause delays. Noticing symptoms is key to negative SV prevention.
• Causes — however, noticing SV issues before they happen is not always possible. Say you’ve calculated SV and determined your team needs to work harder. This isn’t the end of the SV issue. Until you’ve determined what exactly caused the discrepancy in your schedule, you won’t be able to avoid it in the future. And vice versa — if you find out why you have positive schedule variance, you might be able to recreate those conditions and replicate them.
• Recommended actions — what if just working harder to catch up to your schedule isn’t enough? What if you don’t have enough resources to increase work by the needed amount? In that case, some changes are required. According to the PMBOK guide (Sixth Edition), “Schedule variance analysis may result in change requests to the schedule baseline, scope baseline, and/or other components of the project management plan.” Additionally, “Preventive actions may include recommended changes to eliminate or reduce the probability of negative schedule variances.”

Tip #3: Create decision logs

A decision log is a document that shows how and why every important decision was made during the course of a project. You can use a decision log to reduce the time spent on resolving issues that are similar to ones resolved in the past.

Just the baseline of what the decision is can be helpful in all similar situations. However, the other questions listed in the decision log are not to be overlooked.

For example, why was a decision made? 

Let’s say you’re running a pottery shop. There was a delay due to a missing clay shipment. You decided to use some clay from your storage, as you had extra. However, that extra is spent now, and the next time this issue arises, you can’t use the same solution. 

The decision log doesn’t only tell you what solution you can use — it helps you determine whether that solution is still valid as well.

Tip #4: Define a realistic project schedule

If incorrect planning is one of the main causes of negative SV, one of the main tips is to, well, plan correctly. Defining an achievable, well-planned project schedule is the key to preventing SV issues.

Create a work breakdown structure to better understand even the tiniest parts of your project. Gaining a thorough knowledge of the required project tasks will allow you to better organize them in your schedule.

Underestimating the amount of time, the budget, or any other resource for your project will most likely lead to a negative SV. 

If you’re not careful while creating your project schedule, you can cause future delays before work on the project even begins.

Conclusion: Improve project performance with schedule variance calculations

Virtually no project goes by without a delay at some point. You should not be afraid of this issue. But, you also can’t let delays fester.

Schedule variance serves to point out delays in your project, bringing them to your attention. It indicates how much you need to change your intensity of work to make up for the delays. 

As a project manager, you’re expected to pay close attention to your schedule variance. It is a KPI that should not go unnoticed and can bring many benefits to your project — if you use it well.

📖 Schedule variance is just one of the relevant project management concepts you need to understand — for a better understanding of the general subject of project management, explore our Project Management Glossary of Terms.

References: 

• Project Management Institute. (2019). The Standard for Earned Value Management. Project Management Institute. https://www.goodreads.com/en/book/show/45899516
• Project Management Institute. (2017). A Guide to the Project Management Body of Knowledge (PMBOK® Guide)–Sixth Edition. Project Management Institute. https://www.goodreads.com/book/show/34448751-a-guide-to-the-project-management-body-of-knowledge-pmbok-guide-sixth?from_search=true&from_srp=true&qid=rm0H1SKKH1&rank=4
• Project Management Institute. (2021). A Guide to the Project Management Body of Knowledge (PMBOK® Guide)–Seventh Edition. Project Management Institute. https://www.goodreads.com/book/show/58474625-a-guide-to-the-project-management-body-of-knowledge-pmbok-guide-sev
• Dau.edu editorial team (n.d.) Schedule Variance (SV), retrieved January 31, 2023, from https://www.dau.edu/acquipedia/pages/articledetails.aspx#!268