Environmental Impact Score Calculator

Work out environmental impact score instantly with clear inputs, formula shown and shareable results.

About Environmental Impact Score Calculator

A common environmental impact assessment method scores magnitude, spatial extent and duration to give a consequence value, then multiplies by probability. The result is banded to determine whether mitigation is essential, required or unnecessary. Scoring criteria must be defined explicitly for the scores to be defensible.

Formula

Impact score

Consequence = magnitude + extent + duration; impact score = consequence x probability

Worked example

With the default values below, Environmental Impact Score Calculator returns Environmental Impact Score of 33. Change any input above and every figure here is recalculated in your browser.

Inputs used

Magnitude Of Impactaccepts 1–5: 4
Spatial Extentaccepts 1–5: 3
Durationaccepts 1–5: 4
Probability Of Occurrenceaccepts 1–5: 3

Results

Environmental Impact Score: 33
Consequence Score: 11
Score As Percentage Of Maximum: 44.00%
Significance Band: Moderate - mitigation required

Step by step

1Values used
2Impact score
3Environmental Impact Score= 33
4Consequence Score= 11
5Score As Percentage Of Maximum= 44.00
6Significance Band= Moderate - mitigation required

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, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Environmental impact assessment methodologies and significance criteria are prescribed by regulation and guidance. Scoring must be undertaken by competent assessors.

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

Environmental impact assessment methodologies and significance criteria are prescribed by regulation and guidance. Scoring must be undertaken by competent assessors.

Frequently Asked Questions

Why not simply add all four factors?

Because a certain small impact and an unlikely catastrophic one should not score alike. Multiplying consequence by probability captures risk rather than mere magnitude.

Are these scores objective?

No. They structure professional judgement rather than replace it. Transparency about the scoring criteria and reasoning matters far more than the arithmetic.