Percentage Calculator
Every percentage question answered from the same two numbers — what percentage of, what percentage is, and how much it changed.
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How it works
Percentage questions come in four shapes and people mix them up constantly, usually because each one moves the divisor somewhere different. Rather than making you pick the right mode first, this calculator answers all four from the values you enter.
The one worth watching is percentage change, because it is not symmetric. Going from 80 to 100 is a 25% increase, but coming back from 100 to 80 is a 20% decrease — same two numbers, different base.
P% of A = A × P ÷ 100 · A as % of B = A ÷ B × 100 · Change = (B − A) ÷ A × 100
- A — the first value — the starting point for a change
- B — the second value — the end point
- P — the percentage to apply
Worked example
A = 80, B = 100, P = 25
Inputs
Results
Reverse the change and it is −20%, not −25%. Percentage changes never cancel out, which is why a 50% loss needs a 100% gain to recover.
Frequently asked questions
Why is a 25% rise cancelled by a 20% fall?
Because the base changes. The rise is measured against 80 and the fall against 100. The larger the swing, the wider the asymmetry — a 50% fall needs a 100% rise to get back to where it started.
What is the difference between percentage points and percent?
Moving from 5% to 7% is a rise of 2 percentage points, but a 40% increase. Both are correct and they describe very different things — which is why the two units are worth keeping distinct.
How do I reverse a percentage increase?
Divide rather than subtract. To strip a 20% increase off 120, divide by 1.2 to get 100 — subtracting 20% would leave 96, which is the wrong answer.
Is my data sent anywhere?
No. The calculation runs entirely in your browser. Nothing you type is transmitted to us or stored.
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