Week over Week Growth Calculator

What is week-over-week growth?

Week-over-week (WoW) growth measures how a metric changed from one week to the next. It’s the fastest standard time frame for tracking growth and is common at startups, in product teams, and during marketing campaigns where waiting a full month would lose valuable signal.

The formula is the same as any growth rate: subtract last week’s value from this week’s, divide by last week’s value, multiply by 100. If signups were 1,250 last week and 1,410 this week, your WoW growth is 12.8%.

Weekly data is noisy by nature. Holidays, day-of-week effects, and random variation all show up in weekly numbers. That’s why the multi-week analyzer uses a 4-week moving average to surface the real trend.

How this calculator works

The quick calculator handles the simple case: two values, one percentage.

The multi-week analyzer handles up to 52 weeks of data. Enter your values, and it calculates a compound weekly growth rate, detects growth patterns, generates a narrative summary, and charts the trend with a 4-week moving average to smooth out noise.

The moving average is especially useful for weekly data. Raw week-to-week numbers bounce around, making it hard to see whether you’re actually growing. The smoothed line shows direction without the distraction.

The projection section estimates where your metric is heading based on the compound weekly rate. The cone widens for volatile data because the prediction becomes less certain.

When to use WoW growth

Use WoW for metrics that move fast enough to measure weekly. Signups, active users, sessions, and conversion rates during experiments are common examples.

WoW is the default at YC-stage startups. Paul Graham’s advice: “The best thing to measure the growth rate of is revenue. The next best, for startups that aren’t charging initially, is active users.” Measure it weekly.

Use month-over-month growth when weekly data is too noisy to be useful, or when the metric naturally operates on a monthly cycle (MRR, churn, contract renewals). Use year-over-year growth for seasonal businesses or board-level reporting.

Interpreting weekly volatility

A single week’s number rarely means much on its own. Look for patterns across 4-8 weeks before drawing conclusions.

The growth pattern detector in the analyzer above classifies your data automatically. “Volatile” doesn’t necessarily mean bad. It means your weekly swings are large relative to the trend. An early-stage product with a small user base will naturally show volatile weekly growth.

What matters is the direction of the moving average. If the smoothed line is pointing up, individual down weeks are just noise. If the smoothed line flattens or turns down over several weeks, that’s a signal worth investigating.

Common pitfalls

Day-of-week effects can distort weekly numbers. If you measure “weeks” starting Monday but a holiday falls on Monday, that week looks artificially low. Pick a consistent measurement window and stick to it.

Comparing raw WoW growth across different business stages is misleading. A startup with 100 users can post 20% WoW growth. A company with 100,000 users growing at 2% WoW is adding more absolute value. Report both the percentage and the absolute change.

Don’t extrapolate weekly growth rates over long periods. A 5% weekly compound rate sounds modest, but compounded over a year it implies 12x growth. Very few businesses sustain that. Use weekly rates for short-term tracking and monthly or annual rates for longer projections.