Calculate a percentage decrease and the amount it removes.
Result
170
Formula
200 × (1 − 15 ÷ 100) = 170
A 25% reduction
Apply a decrease to a value
25A price drop
From one figure to another
80Halving
A 50% decrease
50Apply a percentage reduction, or measure the drop between two known figures.
The reduced value and the amount removed both appear immediately.
Recovering a percentage fall always needs a larger percentage rise — the tool shows what that would be.
A 20% fall needs a 25% rise to get back to where it started. That asymmetry is genuinely counter-intuitive and worth seeing.
Knowing something fell 15% is less useful than knowing it fell by £45.
A decrease of more than 100% produces a negative value, and the tool explains rather than hiding it.
Find what a value becomes after a percentage reduction, or work out the percentage drop between two figures. Reductions are where percentage intuition fails most often — a 50% fall needs a 100% rise to recover, and consecutive discounts do not simply add together. The tool shows the resulting value, the amount removed, and the percentage, so the arithmetic is unambiguous.
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