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Percentage Calculator – X% of Y, What Percent & Change

Calculate percentages, what-percent, and percent change.

Inputs

Enter your values below.

Result

Your answer appears here.

Enter values and press Calculate — the result appears here.

How it works

The formula behind this calculator.

result = base × (rate / 100)

Convert the percentage to a decimal (divide by 100) and multiply by the base. The inverse — X is what % of Y — is X / Y × 100.

Example: 20% of 50 = 50 × 0.20 = 10

Ref: ISO 80000-1 (Quantities and units)

Tips

💡 'X% of Y' and 'X is what % of Y' are two different questions — pick the right mode above.
💡 Percent change is (new − old) / old × 100, not new − old.
💡 To add X% to a number, multiply by 1 + X/100.

FAQ

How do I calculate percent change?

(New − Old) / Old × 100. A negative result means the value decreased.