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Math / Percentage

Percentage Calculator

Solve the three common percentage questions: find a percentage of a number, determine what percent one amount is of another, or find the percentage change between two values. Each mode uses a clearly defined base to avoid confusing percentage points with percent change. Choose the relationship you know. “P% of X” is X × P/100; “A is what percent of B” is A/B × 100; percent change is (new − old)/|old| × 100.

Your inputs

Make it your own
Calculator settings

Your result
30
%
15% of 200
A part of the whole · 100% ring30%
A part of the whole · 100% ring

Example inputs shown. Adjust them to explore.

A familiar situation

Compare a sale price with the original amount to calculate a discount or percent change.

How to use this calculator

  1. Enter question, percent or first value, base or second value.
  2. Select Calculate to see the answer and its breakdown.
  3. Keep a scenario, change an input and compare the results.

Use consistent units and check the assumptions below before applying the result.

How percentage is calculated

Choose the relationship you know. “P% of X” is X × P/100; “A is what percent of B” is A/B × 100; percent change is (new − old)/|old| × 100. A price moving from 80 to 92 changes by (92−80)/80 × 100 = 15%.

Percent of: P×X/100; part as percent: A/B×100; percent change: (new−old)/|old|×100.
A worked example

A price moving from 80 to 92 changes by (92−80)/80 × 100 = 15%.

Assumptions & useful context

The result depends on the values you enter and the method described above. Displayed numbers may be rounded; calculations use the unrounded values. Check that this model matches your situation before relying on it.

Frequently asked questions

What does a negative change mean?

The new value is below the starting value; the signed result preserves that direction.

Why can percent change be undefined?

A zero starting value cannot serve as the denominator.

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