Percentage Of Calculator

Calculate percentage of a number, percentage ratio, percentage change, and percentage difference.

What is% of?

Result

Proportion Visualisation

20.0%

Summary Sentence

20% of 150 is 30

Step-by-Step Calculation

Algebraic Formula

Formula: Y × (X / 100)

Substitution & Steps

150 × (20 / 100) = 150 × 0.2 = 30

How percentage calculations work

Four common percentage questions answered instantly: What is X% of Y? multiplies Y by X/100 — useful for discounts, tips, and tax calculations. X is what % of Y? divides X by Y and multiplies by 100 — useful to express a part as a fraction of a whole. % change from X to Y? computes (Y−X)/|X| × 100 — shows growth or decline as a percentage. % difference between X and Y compares two numbers using their average as the base.

Built and maintained by Meet Shah · Last updated 1 August 2026

What this tool is used for

Finding a percentage of a number without reaching for a calculator app.
Working out a percentage change between two values.
Reverse-solving the original value from a percentage result.
Working out a discount or a markup and the resulting price together.
Checking a percentage someone else quoted.

Frequently Asked Questions

What are the four modes for?: They are four genuinely different questions. 'What is X% of Y' multiplies (tips, tax, discounts). 'X is what % of Y' divides (a share of a total). '% change from X to Y' measures growth against the start. '% difference' compares two peers. The wrong one is arithmetically right and factually wrong.
Why does percentage difference divide by the average?: To make it symmetric. Comparing 50 and 75 against their average of 62.5 gives 40% whichever order you write them in. Dividing by one of the values instead gives 50% one way and 33% the other — fine when one is a baseline, misleading when neither is.
Why is percentage change divided by the absolute value of the start?: So that the sign of the result means direction of movement, not the sign of the starting number. Going from −80 to −100 is a 25% increase in magnitude; dividing by −80 rather than 80 would flip that to −25% and suggest the value went up when it fell further below zero.
Why is a 20% discount followed by a 20% rise not back where it started?: Because the two percentages are of different bases. £100 less 20% is £80, and 20% of £80 is only £16, so you land on £96. Reversing a p% cut needs a rise of p/(100−p) — about 25% here. The same asymmetry is why a 50% portfolio loss requires a 100% gain to recover.
Are percent and percentage point interchangeable?: No, and confusing them is how statistics get misreported. A rate moving from 4% to 5% has risen one percentage POINT, which is a 25% increase. Both descriptions are correct and they differ by a factor of 25, so the unit has to be stated explicitly.

Common errors and gotchas

Confusing a percentage point with a percentage, where a move from 5% to 6% is one point and a 20% increase.
Adding and then removing the same percentage and expecting the original back, which it never gives.
Using the wrong base for a percentage change, which reverses the sign of the story.
Applying successive percentages additively rather than multiplicatively.
Reversing a discount by adding the same percentage, which under-recovers.