Percentage calculator

Looking for a simple way to calculate percentages? Use this free calculator to find a percentage of a number, work out one value as a percentage of another, or measure the percentage change between two values. It can help with everyday calculations, from discounts to investment growth.

Why use the percentage calculator?

• Quick results: calculate percentages in seconds.
• Three calculations: find a percentage of a value, a proportion or a percentage change.
• Easy to use: enter the numbers and select Calculate.
• Useful every day: work out discounts, taxes, profits and other percentages.

Frequently asked questions

What is a percentage and why is it useful?

A percentage expresses a proportion out of 100. The word comes from the Latin per centum, meaning “by the hundred”. Percentages make it easier to compare parts with a whole or describe changes consistently.

Percentage = (part / whole) × 100

For example, a 20% discount on a £50 shirt saves £10, so the price is £40.

How do I calculate percentages?

To find X% of Y, multiply Y by X / 100. To find what percentage one value is of another, divide the part by the whole and multiply by 100. To calculate percentage change, subtract the original value from the new value, divide by the original value and multiply by 100:

Percentage change = ((new value − original value) / original value) × 100

• 15% of £200: £200 × 15 / 100 = £30.
• 50 as a percentage of 200: 50 / 200 × 100 = 25%.
• Change from £100 to £150: (150 − 100) / 100 × 100 = 50%.

The original value must be greater than zero for the percentage-change calculation. This calculator requires positive numbers for all three calculations.

How are percentages used in real life?

• Finance: £1,000 earning 5% interest for one year becomes £1,050 before any fees or tax.
• Sales: a 30% discount on an £80 item reduces the price to £56.
• Research: a decrease from 1,000 hectares of forest to 900 hectares is a 10% reduction.
• Health statistics: percentages can describe a proportion of patients experiencing an outcome.

What is the difference between percentages and percentage points?

A percentage change is relative to the original value; percentage points measure the arithmetic difference between two percentages. For example, an interest rate rising from 2% to 3% increases by one percentage point, or 50% relative to the original rate. A discount rising from 10% to 20% increases by 10 percentage points, or 100% relative to the original discount.

Can a percentage calculation be inaccurate?

Results depend on the numbers entered and may be affected by rounding. A large percentage change from a small starting value can also be misleading without context: a rise from £1 to £2 is 100%, but the difference is £1. This calculator displays results rounded to two decimal places.

Why use a calculator instead of calculating by hand?

A calculator saves time and can reduce arithmetic mistakes. For example, 17.5% of £342 is £59.85. For a sequence of calculations, such as a discount followed by VAT, calculate each step separately. On a £600 price before VAT, a 15% discount gives £510; adding 20% VAT gives £612. Retail prices normally include VAT, so check the price basis before applying it.