Percentage Calculator

1. Choose the calculation that matches your question.
2. Enter the required values; the result and formula update as you type.
3. Use the Copy button beside a result to copy it, or Reset to clear all rows.

Percentage Calculator

Percentages compare values, describe changes, and express a part of a whole. The calculation you need depends on the information you already have. Finding 20% of 150, for example, is different from asking what percent 30 is of 150. The six calculators below let you enter the values you know and get the corresponding result. Results update as you type, each one shows its formula, and you can copy it individually.

Calculate a percentage of a number

Use this when you know the percentage and number and want the amount. For example, 20% of 150 = 30, because (20 ÷ 100) × 150 = 30. This is useful for discounts, portions, commissions, tax amounts, tips, and other parts of a known value.

Formula: percentage of a number = (percentage ÷ 100) × number

Find what percent one number is of another

When you know a part and a whole, divide the part by the whole and multiply by 100. For example, 30 is (30 ÷ 150) × 100 = 20% of 150. This is useful for scores, completion rates, proportions, and comparisons. The whole must not be zero.

Formula: percentage = (part ÷ whole) × 100

Find the whole from a percentage

Work backwards when you know the part and its percentage. If 30 is 20% of a number, that whole is 30 ÷ (20 ÷ 100) = 150.

Formula: whole = part ÷ (percentage ÷ 100)

Calculate percentage change

Compare a starting value with a new value to see how much it changed relative to the start. A change from 100 to 120 is (120 − 100) ÷ 100 × 100 = 20%, an increase. A change from 100 to 80 is −20%, a decrease. The starting value must not be zero.

Formula: percentage change = ((new value − starting value) ÷ starting value) × 100

Increase or decrease a value by a percentage

To increase 200 by 15%, calculate 200 × (1 + 15 ÷ 100) = 230. To decrease 200 by 15%, calculate 200 × (1 − 15 ÷ 100) = 170. These calculations are useful for price changes, discounts, reductions, allowances, and quantities.

Increase formula: original value × (1 + percentage ÷ 100)
Decrease formula: original value × (1 − percentage ÷ 100)

How to use the Percentage Calculator

1. Choose the calculator that matches your question.
2. Enter the required values.
3. Review the result and displayed formula as they update.
4. Use Copy to copy an individual result, or Reset to clear all calculations.

Understanding percentages

A percentage expresses a value relative to 100: 50% means 50 out of 100, 25% means 25 out of 100, and 10% means 10 out of 100. The same percentage represents different amounts when applied to different numbers: 10% of 100 is 10, while 10% of 500 is 50. The reference value matters.

Percentage change and percentage increase

Percentage change compares a starting value with a new value. Increasing a value by a percentage applies a specified increase to that value. For example, a change from 100 to 120 is a 20% increase, and increasing 100 by 20% gives 120. They can produce the same numbers while answering different questions.

Percentage decrease and percentage change

If a value changes from 100 to 80, the change is a 20% decrease. Decreasing 100 by 20% also gives 80. Choose the calculation that matches whether you are comparing two values or applying a known rate.

When is a percentage calculator useful?

Use percentage calculations to work out discounts and price changes, compare scores with a possible total, measure business changes in revenue or quantities, express one number as a share of another, or find an original whole from a known part.

Errors and zero values

Some calculations divide by a reference or starting value, which must be nonzero. If you see an error, check the base value for the selected calculation.

Copy and reset

Each result has its own Copy button. Reset clears all inputs and results so you can start again.