The calculator
Use the forecast as it stood at the start of the quarter, before the mid-quarter revisions. Any currency; the result is in percentages. Nothing you enter leaves this page.
The formula
For each quarter:
Accuracy = 100 − (|Actual − Forecast| ÷ Forecast × 100), floored at zero.
Bias = (Actual − Forecast) ÷ Forecast × 100. Positive bias means actuals came in above forecast (under-forecasting); negative means below (over-forecasting).
The averages use the valid quarters entered, with equal weight for each quarter. A quarter with a forecast of zero is excluded because this formula divides by the forecast. Blank or negative values are also excluded. Working it by hand: a forecast of 1,000 and an actual of 880 is an error of 120, which is 12% of forecast, so accuracy is 88% and bias is −12%.
The denominator is the forecast. The accuracy calculation uses the absolute difference, while bias retains its direction. This differs from measures that divide by actual revenue. Use the same definition when comparing results.
Interpreting the result
This calculator uses one forecast-relative measure. It does not establish an industry benchmark or tell you whether a forecast is safe to use for a particular decision. Choose a tolerance appropriate to your business, deal sizes and planning needs.
Look at individual periods as well as the average. Positive and negative errors can cancel out in average bias, and large deals can dominate a quarter. Investigate the deals behind the differences before deciding what to change.
Want a probability-validated forecast built from your own win/loss history? That is part of the sales process audit and pipeline review.
This calculator is free to use within your firm. Please link to this page rather than republishing it.