Mean Absolute Percentage Error Calculator

Calculate MAPE and understand its limitations near zero.

About Mean Absolute Percentage Error Calculator

MAPE is scale-free and intuitive but breaks down when actuals approach zero, since dividing by a tiny number produces enormous percentages. Weighted MAPE avoids that by working on totals. For intermittent demand with many zero periods, MAPE is unusable and weighted forms or absolute measures should be used instead.

Formula

Mean Absolute Percentage Error

MAPE = Σ|actual − forecast| ÷ |actual| ÷ n × 100

MAPE: Scale-free but undefined when actual values are zero
weighted MAPE: Uses totals rather than averaging ratios, avoiding small-denominator distortion

Worked example

With the default values below, Mean Absolute Percentage Error Calculator returns Mean Absolute Percentage Error of 7.0000%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Sum of absolute percentage errorsminimum 0 %: 42 %
Number of periodsminimum 1: 6
Total actual valueminimum 0: 6,000
Total forecast valueminimum 0: 6,300

Results

Mean Absolute Percentage Error: 7.0000%
Forecast Accuracy: 93.0000%
Weighted Absolute Percentage Error: 5.0000%
Overall Bias: 5.0000%
Rating: Highly accurate

Step by step

1Values used
2Mean Absolute Percentage Error
3Mean Absolute Percentage Error= 7.0000
4Forecast Accuracy= 93.0000
5Weighted Absolute Percentage Error= 5.0000
6Overall Bias= 5.0000
7Rating= Highly accurate

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or fees or charges into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Mean Absolute Percentage Error calculated?

MAPE = Σ|actual − forecast| ÷ |actual| ÷ n × 100 MAPE is scale-free and intuitive but breaks down when actuals approach zero, since dividing by a tiny number produces enormous percentages. Weighted MAPE avoids that by working on totals.

Why does Mean Absolute Percentage Error matter?

For intermittent demand with many zero periods, MAPE is unusable and weighted forms or absolute measures should be used instead.

What values do I need to enter?

This calculator takes 4 inputs: Sum of absolute percentage errors, Number of periods, Total actual value, Total forecast value. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.