Week-on-Week Calculator
Week-on-Week calculations can be helpful when comparing 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 helpful 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 to help you better understand this metric.
Week-on-Week Calculator
Week-on-Week Definition
Week-on-Week (or WoW) calculations compare one period to the same period the week before. The data doesn’t necessarily have to cover the whole week or be from this week; however, it can in both cases.
You can also compare an individual day (e.g., this Friday versus last Friday) or a specific metric, product, or page.
The key point is that you are comparing this week’s time frame to last week’s equivalent time frame.
Week-on-Week Formula
Use this equation to calculate the change in metrics from one week to the next.
Week-on-Week Change =
((Any Metric ÷ Same Metric from previous week) -1) x100
Alternative Equations
The above equation is the most convenient Week-on-Week calculation to input into 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:
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 helpful to see whether 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 helpful 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 compare 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, includes every day of the week. This means that if your website sees different activity levels on weekends than weekdays (if it’s a B2B site, for instance), comparing the past seven days to the previous seven days won’t be affected.
Finally, a week is a reasonable time frame to compare performance because it’s likely that not much will have changed externally from the previous week. For example, people might react differently to the same thing in the summer and winter. 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.
When shouldn’t I use Week-on-Week calculations?
Week-on-Week comparisons are not helpful 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 significant 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?
Mid-level and management often want to see this kind of reporting. They are involved enough in the day-to-day running of things to want to ensure they will 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, particularly expensive, or troublesome, then it’s likely 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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