Sales Forecast Calculator

You enter a baseline sales figure and/or historical monthly sales, along with a growth rate and optional seasonal or one-off adjustments. The calculator applies your chosen method (simple growth, average historical growth, or weighted forecast) to project future sales instantly in your browser.

Simple growth compounds your entered growth rate each period. Average historical growth calculates the average month-over-month change from your historical data. Weighted forecast also uses historical data but gives more influence to your most recent months, which can better reflect current momentum.

You can enter as few or as many historical months as you have, up to 12. If you choose average or weighted methods without at least two historical entries, the calculator automatically falls back to your entered growth rate and clearly notes this in the assumptions.

The seasonal adjustment applies a repeating 12-month cyclical pattern to your projection, scaled by the percentage you enter, to simulate typical seasonal peaks and troughs on top of your underlying growth trend.

Yes. Tick "Enable decline scenario" to allow negative growth rates. Without this enabled, the calculator will not accept negative growth rates and floors any projection at zero to avoid invalid negative sales figures.

No. All calculations happen locally in your browser, and no financial data is stored or transmitted, except if you choose to generate the optional AI interpretation, which sends only summary figures for that single request.