Week Over Week Calculator

Compare this week's value to last week's to get the dollar change, the percent change, an annualized growth rate, and a compounded projection for future weeks.

Quick Facts

Formula
WoW % = (Current − Previous) / Previous × 100
The same pattern used for month-over-month or year-over-year change, applied to a one-week interval.
Projection
Projected = Current × (1 + rate)^weeks
Assumes this week's rate repeats every week — a straight-line extrapolation, not a forecast.

Your Results

Calculated
WoW change
-
Current minus previous week
WoW % change
-
Change relative to previous week
Annualized rate
-
This week's rate compounded over 52 weeks
Projected value
-
If the weekly rate holds steady

Ready

Enter last week's and this week's values, then press Calculate.

How the Week Over Week Calculator works

Week-over-week (WoW) change compares a metric this week to the same metric last week — revenue, sales, active users, website traffic, or any figure tracked on a weekly cadence. It is the same idea as month-over-month or year-over-year change, just applied to a seven-day interval, and it is one of the most common ways operators and analysts spot short-term momentum or slowdown.

The formula

For a Previous week value and a Current week value, the calculator computes:

WoW change = Current − Previous

WoW % change = (Current − Previous) / Previous × 100

The previous week's value must be greater than zero, since dividing by zero makes the percentage undefined. To put the single week's rate on a comparable yearly footing, the calculator also compounds it over 52 weeks: Annualized rate = (1 + WoW rate)52 − 1, where WoW rate is the WoW % change expressed as a decimal.

Worked example

If last week's revenue was $10,000 and this week's is $10,800, the change is $800 and the percent change is 800 / 10,000 × 100 = +8.00%. Compounding an 8% weekly rate over 52 weeks gives an annualized rate of roughly +5,371% — a reminder that annualizing a single strong (or weak) week produces an extreme number, useful for scale comparisons but not a realistic year-long forecast.

Projecting future weeks

The projection assumes the current week's percent change repeats every week going forward: Projected value = Current × (1 + WoW rate)weeks. In the example above, projecting 4 more weeks at a steady +8% weekly rate takes $10,800 to roughly $14,694. This is a straight-line compounding exercise, not a model of seasonality, marketing spend, or diminishing returns — treat it as a "what if this rate holds" reference point, not a prediction.

Why weekly comparisons are noisy

  • Day-of-week effects: a metric that is naturally higher on weekends or during a promotion can swing WoW% sharply even with no change in underlying trend.
  • Small-base effects: percent changes on a small previous-week value look dramatic even when the absolute change is minor.
  • Single-week noise: one unusually good or bad week compounded to an annualized rate can look far more extreme than the real year-long trend — pair WoW with a multi-week moving average before acting on it.

Frequently Asked Questions

How is week-over-week (WoW) change calculated?
WoW percent change equals (Current week value minus Previous week value) divided by Previous week value, times 100. The absolute change is simply Current minus Previous. For example, going from 10,000 to 10,800 is a change of +800, or +8.00%.
How does the projection assume future weeks behave?
The projected value assumes the current week's percent change repeats every week going forward (compounding), using Projected = Current x (1 + weekly rate) raised to the number of weeks. It is a straight-line extrapolation of one data point, not a forecast that accounts for seasonality, one-time events, or slowing growth.
What does the annualized rate mean?
The annualized rate compounds the single week's growth rate over 52 weeks: (1 + weekly rate)^52 minus 1, expressed as a percent. It converts a one-week move into a comparable yearly figure, which is useful for sizing whether a weekly change is small or large, but it is highly sensitive to noise in any single week.
Why do I need the previous week's value to be greater than zero?
Percent change is undefined when the denominator is zero, so the calculator requires a previous week value above zero. If a metric starts from zero (a brand-new product, for instance), report the raw change in units instead of a percentage for that first week.

Related calculators