Understand your error metric before comparing forecasts.
TL;DR: MAPE and WAPE measure error differently. This calculator explains a percentage you supply and shows its 100-minus-error value. It does not assign an industry rank: we do not have a representative comparison dataset for your metric, category and horizon.
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| Metric | Calculation | Limit to check |
|---|---|---|
| MAPE | 100 × mean(|actual − forecast| / actual) | Undefined when an actual value is zero; unstable near zero. |
| WAPE | 100 × sum(|actual − forecast|) / sum(actual) | Undefined when total actual demand is zero. It can be higher or lower than MAPE. |
| 100 − error | 100 minus your chosen percentage error | A reporting convention, not an industry rank. It can be negative when error exceeds 100%. |
Use non-negative demand quantities and compare the same metric, products and forecast horizon. See Forecasting: Principles and Practice for error definitions and percentage-error limitations, or our bias and accuracy guide for a worked example. To see how Forthcast reports it, read forecast accuracy and bias in Forthcast, and how to measure forecast accuracy SKU by SKU. This calculator converts a supplied percentage; it does not validate the underlying orders or forecasts.
Forthcast provides store-wide demand forecasts, reorder alerts and draft purchase orders for merchant review. The Basic Plan is $19.99/month with a standard 14-day trial. Check the forecasts against your own history and buying decisions.
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These are self-selected submissions, not verified merchant outcomes or a representative industry sample. Different metrics and horizons are not pooled into an accuracy ranking. A future report would need a defined methodology and sufficient comparable data.