Percentage Calculator

Calculate percentages, percentage differences, and percentage changes.

About the Percentage Calculator

Calculate percentages, percentage differences, and percentage changes without doing the mental math yourself.

How the Percentage Calculator works

Percentage Difference and Percentage Change look similar but answer different questions. Percentage Difference is symmetric — it doesn't matter which value you enter first, and it compares both values against their average. Percentage Change is directional — it treats one value as the "old" value and measures how far the "new" value moved away from it, reporting the result as an increase or decrease.

How to use the Percentage Calculator

Choose a calculation type using the radio buttons — the input fields below update to match.
"Percentage of a Number" also lets you choose what to solve for: the result, the percentage, or the base value.
"Increase/Decrease by Percentage" lets you choose the direction of the adjustment.
Enter the relevant values for the selected type.
Press Calculate to see the result and a plain-language explanation.

Tips for the Percentage Calculator

Use Percentage Difference to compare two values with no inherent "before/after" relationship, and Percentage Change when one value came before the other.

Formula used by the Percentage Calculator

Percentage of a Number: Z = Y × (X ÷ 100)
Increase/Decrease by Percentage: Result = Y × (1 ± X ÷ 100)
Percentage Difference: |V1 − V2| ÷ ((V1 + V2) ÷ 2) × 100
Percentage Change: (New − Old) ÷ Old × 100

Example: Percentage Calculator

Finding 20% of a number

Percentage (X): 20%
Base value (Y): 150

Result: 30

Z = 150 × (20 ÷ 100) = 30 — the same math as finding a 20% tip on a $150 bill.