Week-on-Week Calculator

Week-on-Week calculations can be helpful when trying to compare your short term performance. By using last week’s performance as a baseline, you can see whether your performance this week is higher or lower.

We have provided a useful online Week-on-Week Calculator below to work out your change in performance.

Feel free to experiment with different scenarios using our Week-on-Week Calculator in order to help you better understand this metric.


Week-on-Week Calculator


Week-on-Week Definition

Week-on-Week (or WoW) calculations simply mean comparing one period to the same period in the week before. It doesn’t necessarily have to cover the whole week, or be from this week – however, in both cases it can.

You can also look at an individual day (as in this Friday versus last Friday), or at a specific metric, product or page.

The key point is that you are comparing a time frame from this week to the equivalent time from last week.


Week-on-Week Formula

Use this equation to calculate the change in metrics from one week to the next.

Week-on-Week Equation: ((Any Metric/Same Metric from previous week)-1)x100Click to enlarge

Week-on-Week Change =
((Any Metric ÷ Same Metric from previous week) -1) x100 


Alternative Equations

The equation used above is the most convenient Week-on-Week calculation to input in a calculator. However, there are other ways to calculate Week-on-Week changes. The most commonly used equation is:

Week-on-Week = ((this week – previous week) ÷ previous week) x100

While this equation comes out the same (try it!), you have to input the numbers from the previous week twice. This makes it a slightly more annoying calculation to use.

If you want to calculate Week-on-Week changes in Excel, you can use the following formula:

Week-on-Week Excel formula

To use this Week-on-Week formula you need to change the B2 and C2 parts of it as appropriate


When should I use Week-on-Week calculations?

Week-on-Week calculations can be helpful when you are looking at performance over a short period of time and want to see if it is significant. For example, if you had a really good Friday for sales and you want to quickly check how good, you can compare it to the week before.

This sort of reporting can be useful to see if something you did recently made a difference. For example, if you ran a marketing campaign last week, and you want to know if this week is doing better because of it.

It is also useful because many statistics are cyclical on a week by week basis. For example, blog posts typically perform best on Mondays. This means that if you compare a Monday to another Monday, you’ll be comparing days with an equal chance of doing well. However, if you compare it to another day of the week, your stats will be skewed by changes in human behaviour.

Another good thing about Week-on-Week calculations is that a week, of course, contains every day of the week. This means that if your website sees different levels of activity on weekends than weekdays (if it’s a B2B site for instance) then comparing the past 7 days to the previous 7 days won’t be affected by this.

Finally, a week is a reasonable time frame to compare performance over because it’s likely that not much will have changed externally from the week before. For example, people might react differently in the Summer and Winter to the same thing. However, they are likely to react roughly the same in the first week of summer versus the second week of summer. By having a short term comparison you can more-or-less exclude external factors from affecting your results.

Note: Any time you click “Compare to: previous period” in a platform (such as Google Analytics), and you’ve chosen a week as your time frame – you will be using Week-on-Week reporting.


Week-on-Week Example

Week 1 will be compared to Week 2


When shouldn’t I use Week-on-Week calculations?

Week-on-Week comparisons are not useful for long term planning. A week is a relatively short period of time, and so changes you see compared to last week are usually not enough to base big decisions on.

For big decisions, you should look at longer time frames. Depending on the type of metric, this could be Month-on-Month, Quarter-on-Quarter, or Year-on-Year comparisons.


Who are Week-on-Week comparisons useful for?

It is often mid-level and management who want to see this kind of reporting. This is because they are involved enough in the day-to-day running of things to want to ensure they are going to hit short term targets.

Top-level management will likely only want to see broader strokes and long term trends unless they are particularly invested in a project.

Low-level management is typically interested in both short and long term reporting.

If a project is new or particularly expensive or troublesome, then it’s not unlikely that Weekly updates like this will be requested. In general, though, these sorts of weekly snapshots are more of a curiosity than a vital reporting tool for most of any company.


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