Try one

% of a number

2 dp

What is 15% of 240?

15 ÷ 100 × 240

15% of the whole

Remaining

204

Whole

240

As a fraction

15/100

Every reading of these two numbers

% of15% of 240 = 36

Share15 is 6.25% of 240

Change15 → 240 is 1,500%

Increase15 + 240% = 51

Decrease15 − 240% = -21

Percentage15

Number240

Answer36

Rounding2 dp

Numbers

Back to the tool

Percentage Calculator

Solve the percentage question you actually have: a percent of a value, one value as a share of another, percentage change, an increase or decrease, or the difference between two values. Every mode keeps the formula visible and the result shareable.

Percentage questions: 5
Decimal places: 0–6
Increases and decreases: ±
Shareable calculation: 1 link

Step by step

How to use it

01
01Choose the question
Select percent of, share, change, adjustment, or percentage difference so the two inputs have unambiguous roles.
02
02Enter both values
The field labels restate the question rather than leaving you to remember which number goes where.
03
03Check the visible formula
Use the arithmetic under the answer to verify the baseline and direction.
04
04Set useful precision
Round the display only as far as the source values justify, then copy the answer or share the calculation.

Worked example

A price rises from $80 to $92

Old value: $80
New value: $92

Percentage change

change = new − old = 12
rate   = change / |old|
       = 12 / 80
       = 0.15 = 15%

Absolute change: +$12
Percentage change: +15%
New as share of old: 115%

Percentage change divides by the old value. Reversing the journey from $92 to $80 is a 13.04% decrease, not 15%, because the baseline changed.

Why this one

The denominator is the whole story

Percent means per hundred

15% is the ratio 15/100, or 0.15. Multiplying a value by 0.15 finds that share.

Change needs a baseline

Percentage change uses the old value in the denominator, so direction matters.

Difference treats both values symmetrically

Percentage difference divides the gap by the average magnitude, making it useful when neither value is the baseline.

Successive changes compound

Up 20% and down 20% do not cancel: 1.2 × 0.8 = 0.96, a net 4% decrease.

The judgement call

Which percentage calculation do you need?

Find 15% of 240
% of
Multiply the whole by the percentage as a decimal.
Find what share 36 is of 240
Share
Divide the part by the whole.
Compare an old value with a new one
% change
The old value is the explicit baseline.
Compare two measurements with no baseline
% difference
The average magnitude treats both sides equally.

Reference

The numbers behind it

Percent of: p/100 × value
Share: part / whole × 100
Change: (new − old) / |old| × 100
Difference: |a − b| / ((|a| + |b|)/2) × 100

FAQ

Questions, answered plainly

How do I calculate a percentage of a number?

Divide the percentage by 100 and multiply by the number. For example, 15% of 240 is 0.15 × 240 = 36.

How do I find what percentage one number is of another?

Divide the part by the whole and multiply by 100. A part of 36 out of 240 is 15%.

How is percentage change calculated?

Subtract the old value from the new value, divide by the absolute old value, and multiply by 100. A positive result is an increase and a negative result a decrease.

Why do equal percentage increases and decreases not cancel?

The second percentage applies to a changed base. Increasing 100 by 20% gives 120; decreasing 120 by 20% removes 24 and leaves 96.

What happens when the original value is zero?

Ordinary percentage change is undefined because it would require division by zero. Report the absolute change or provide a domain-specific convention instead.

Inputs and calculations remain in your browser. A share link contains only the values and settings you choose to share.

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