calculateFree Online Forecast Bias Calculator

This web page allows you to paste in your forecast versus actuals data and calculates forecast bias using the Normalised Forecast Metric method, in a similar way to our Prophecy demand forecasting software.  If you supply forecast versus actual data for a single item over sequential time periods the calculator will also calculate the Tracking Signal.

The calculation of forecast bias and the bias measures used here are described in our knowledgbase article, "Forecast Bias in Accuracy Measurement".

Privacy Note:
This page runs entirely with client-side javascript. The forecast versus actual data you supply stays on your computer and is NOT transmitted back across the internet.


  1. Enter a list of time period or item labels, forecasts and actuals into the text area below, load from Excel or paste them in from the clipboard.  For Excel the data must be on the first 'tab' and the file format must be ".xlsx" (Open Office XML / Excel 2007 or later).
    Here is a small example, using commas as the delimiter, though semi-colons, tabs or pipe characters ('|') will work too.  Your data can have an optional header row.  Field 1 is the item description (which can be any text that describes the observation), field 2 is the forecast and field 3 is the actual sale:
    Item 1,350,411
    Item 1,200,192
    Item 1,500,454
  2. Click the Submit button and view the results.
  3. Sort the details view in ascending or descending order by clicking any of the header cells.  Shift+click will sort on absolute values (i.e. ignoring the sign).