Three modes — all live, no button needed
Add this Percentage Calculator to your website or blog for free — just paste this code:
The Percentage Calculator handles all the most common percentage problems in one place. Whether you need to find what percentage one number is of another, calculate a percentage of a value, work out the original number before a percentage increase or decrease was applied, or find the percentage change between two figures, this tool covers every scenario. Just select the type of calculation you need, enter your numbers, and the answer appears instantly alongside a step-by-step explanation so you can see exactly how the result was reached.
Percentages appear constantly in everyday life — discounts, tax rates, tips, exam scores, pay rises, investment returns, nutritional information, and statistical reporting all use them. Despite being familiar, percentage calculations are a frequent source of confusion because there are several distinct question types that look similar but use different formulas. "What is 20% of 80?" (answer: 16) uses the formula part = percent × whole ÷ 100. "What percentage of 80 is 16?" reverses it: percent = part ÷ whole × 100. "80 increased by 20% equals what?" uses whole × (1 + percent/100) = 96. And "what was the original value if 96 is 20% more than it?" works backwards: original = new value ÷ (1 + percent/100) = 80. The calculator correctly identifies and applies each formula based on the question type you select.
One subtlety worth knowing is that percentage increases and decreases are not symmetrical. If a price rises by 50% and then falls by 50%, you do not end up back where you started — the fall is applied to the larger post-rise value. A £100 item that rises 50% to £150 and then falls 50% becomes £75, not £100. This asymmetry matters when comparing investment returns, price movements, or any scenario involving successive percentage changes. The percentage change calculator shows you the direction and magnitude of a single change; for compounding successive changes, multiply the multipliers together rather than adding the percentages.
Multiply the number by the percentage and divide by 100. For example, 20% of 350 = 350 × 20 ÷ 100 = 70. Equivalently, convert the percentage to a decimal (20% = 0.20) and multiply: 350 × 0.20 = 70.
Divide the part by the whole and multiply by 100. For example, to find what percentage 45 is of 180: 45 ÷ 180 × 100 = 25%. Always make sure you divide the part by the correct total (the whole), not the other way round.
Subtract the original value from the new value, divide by the original value, and multiply by 100. Formula: ((New − Old) ÷ Old) × 100. A positive result is an increase; negative is a decrease.
Percentage points measure the arithmetic difference between two percentages. If interest rates rise from 2% to 5%, that is 3 percentage points — but expressed as a percentage change it is (5−2)/2 × 100 = 150%. Confusing the two is a common source of misinterpretation in financial and statistical reporting.
Because the second percentage is applied to the new (larger) value. If £100 rises 50% to £150 and then falls 50%, the fall is 50% of £150 = £75, leaving £75, not £100. Successive percentage changes compound multiplicatively, not additively.