Charity Donation Impact Calculator

Work out charity donation impact instantly with clear inputs, formula shown and shareable results.

About Charity Donation Impact Calculator

Tax relief is added first, overheads are then deducted, and the remainder is divided by the cost of delivering one unit of impact. Tax relief can add a quarter to a gift at no cost to you, which usually outweighs the difference in overhead ratios between comparable charities.

Formulas

Programme funding

to programme = donation x (1 + tax relief) x (1 - overhead share)

Units funded

units = programme funding / cost per unit

Worked example

With the default values below, Charity Donation Impact Calculator returns Units of impact funded of 22.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Donation amountminimum 0.01: 500
Cost to deliver one unit of impactminimum 0.01: 25
Share spent on overheadsaccepts 0–90 %: 12 %
Tax relief added to the giftaccepts 0–100 %: 25 %

Results

Units of impact funded: 22.00
Amount reaching the programme: $550.00
Value of the gift including tax relief: $625.00
Amount absorbed by overheads: $75.00

Step by step

1Values used
2Programme funding
3Units funded
4Units of impact funded= 22.00
5Amount reaching the programme= 550.00
6Value of the gift including tax relief= 625.00
7Amount absorbed by overheads= 75.00

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 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.

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 the Charity Donation Impact figure worked out?

to programme = donation x (1 + tax relief) x (1 - overhead share). Tax relief is added first, overheads are then deducted, and the remainder is divided by the cost of delivering one unit of impact.

Why does this matter?

Tax relief can add a quarter to a gift at no cost to you, which usually outweighs the difference in overhead ratios between comparable charities.

What do I need to enter?

Enter donation amount, cost to deliver one unit of impact, share spent on overheads, tax relief added to the gift. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.