Percentage Calculator

To calculate the percentage of a number, divide the percentage by 100, then multiply by the number. For example, to find 15% of 240: 15 ÷ 100 = 0.15, then 0.15 × 240 = 36. So 15% of 240 is 36.

Formula: Result = (Percentage ÷ 100) × Number

Steps: 1) Divide the percentage by 100 to turn it into a decimal. 2) Multiply that decimal by the number. 3) The product is your answer.

Worked example — 12% of 52,000: 12 ÷ 100 = 0.12, then 0.12 × 52,000 = 6,240.

On most calculators, to find a percentage of a number you type the number, press ×, type the percentage, then press the % key — for example 240 × 15 % returns 36. On calculators without a % key, multiply by the decimal instead: 240 × 0.15 =.

With a % key: Type the base number, press ×, type the percentage, press %, then = if needed. Example: 240 × 15 % = 36.

Without a % key: Convert the percentage to a decimal (15% → 0.15), then multiply: 240 × 0.15 = = 36.

To find what percent one number is of another: divide the part by the whole, then multiply by 100 — 162 ÷ 206 × 100 = 78.64%.

To find what percent one number is of another, divide the first number (the part) by the second number (the whole), then multiply by 100. For example, 162 is what percent of 206? 162 ÷ 206 = 0.7864, × 100 = 78.64%.

Formula: Percent = (Part ÷ Whole) × 100

To calculate a percentage increase or decrease, subtract the old value from the new value, divide the result by the old value, then multiply by 100. A positive result is an increase; a negative result is a decrease. From 200 to 250 is a 25% increase.

Formula: Percentage change = ((New − Old) ÷ Old) × 100

Increase example (200 → 250): 250 − 200 = 50, 50 ÷ 200 = 0.25, × 100 = +25%.

Decrease example (250 → 200): 200 − 250 = −50, −50 ÷ 250 = −0.20, × 100 = −20%.

Percentage difference compares two values without treating either as the starting point. Subtract the smaller from the larger, divide by the average of the two, then multiply by 100. For 40 and 60: difference 20 ÷ average 50 = 0.4, × 100 = 40%.

Formula: Percentage difference = (|A − B| ÷ ((A + B) ÷ 2)) × 100

Use percentage difference when neither number is a clear "before"; use percentage change when one value comes first in time.

A reverse percentage finds the original number before a percentage was added or removed. If a price is 120 after a 20% increase, divide by 1.20 to get the original: 120 ÷ 1.20 = 100. For a discount, divide by (1 − rate) instead of (1 + rate).

Formulas: Original (after increase) = Final ÷ (1 + Rate ÷ 100)  |  Original (after discount) = Final ÷ (1 − Rate ÷ 100)

Example — £120 includes 20% tax; what was the pre-tax price? 120 ÷ (1 + 0.20) = 120 ÷ 1.20 = £100.

Common everyday percentage calculations and how to do them: