Percentage Calculator

Find X% of a number, or work out what percent one number is of another.

By CalcHub Editorial · Last reviewed 2026-10-21

Quick answer

Formula: Percent of a number: Result = (X ÷ 100) × Number · What percent: Result = (Part ÷ Whole) × 100
Worked example — Result: 30.00 (full example below).

Percentage Calculator

Worked example result

Result	30.00
Same value as a decimal fraction	0.2000

20% of 150 is 30. Switch to the second mode with A = 30 and B = 150 and you get the reverse answer: 30 is 20% of 150.

Diagram: how the Percentage Calculator works — you enter Calculation type, First value — X (the %) or A (the part), Second value — the number, or B (the whole); it applies the formula Percent of a number: Result = (X ÷ 100) × Number · What percent: Re…; and the worked example gives Result: 30.00.

How the Percentage Calculator works — the inputs, the formula, and a worked example (Result: 30.00).

A percentage is a fraction out of 100 — 25% simply means 25 out of every 100. This calculator handles the two questions people ask most: what is a given percent of a number, and what percent one number is of another.

Switch the mode to change the question. In the first mode you enter a percentage and a number; in the second you enter a part and a whole, and the calculator returns the percentage the part represents.

The formula

Percent of a number: Result = (X ÷ 100) × Number · What percent: Result = (Part ÷ Whole) × 100

Worked example

20% of 150 is 30. Switch to the second mode with A = 30 and B = 150 and you get the reverse answer: 30 is 20% of 150.

The example is pre-loaded in the result panel — press Calculate with your own numbers to replace it.

Frequently asked questions

How do I calculate a percentage by hand?

Divide the percentage by 100 and multiply by the number. For 20% of 150: 0.20 × 150 = 30. To find what percent A is of B, divide A by B and multiply by 100.

Can a percentage be more than 100%?

Yes. 150% of 80 is 120, and if a part is bigger than the whole — say 250 out of 200 — the answer is 125%. Percentages above 100% simply mean more than the whole amount.

How do I find the original number from a percentage?

Divide the part by the percentage expressed as a decimal. If 30 is 20% of a number, the number is 30 ÷ 0.20 = 150.

Category: Math calculators

Sources & methodology

This calculator applies the formula shown on this page exactly as written, using the standard definitions for its inputs. Results are computed from the values you enter — no data is stored — and are rounded only for display.

Content last reviewed 2026-10-21 by CalcHub Editorial.

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