A percentage calculator takes the fiddliest everyday math — discounts, tips, grades, growth figures — and answers it in seconds. Enter two numbers and this free tool works out what X percent of Y is, what percentage one number is of another, or the percent increase or decrease between two values.
Every answer uses the standard percentage formulas and appears instantly as you type. There is no sign-up and nothing leaves your browser: your numbers stay on your device.
Every percentage problem reduces to one of three formulas. Once you know which one fits, the arithmetic is simple — and the calculator above applies the right one for you automatically.
Formula: (X ÷ 100) × Y. Worked example: 20% of 150. Divide 20 by 100 to get 0.20, then multiply by 150 — the answer is 30. Use this mode for discounts ("25% off"), tips ("add 15%") and portions ("take 10% for savings").
Formula: (X ÷ Y) × 100. Worked example: 30 is what percent of 150? Divide 30 by 150 to get 0.20, then multiply by 100 — the answer is 20%. Use this mode for grades ("45 out of 60"), progress ("I have done 8 of 10 tasks") and shares ("our region is 3 of 12 stores").
Formula: ((new − old) ÷ old) × 100. Worked example: a salary rises from £30,000 to £33,000. Subtract to get £3,000, divide by £30,000 to get 0.10, multiply by 100 — a 10% increase. A positive answer always means growth.
Same formula: ((new − old) ÷ old) × 100 — a negative answer means a decrease. Worked example: a price falls from £80 to £60. Subtract to get −£20, divide by £80 to get −0.25, multiply by 100 — a 25% decrease. The tool shows the direction for you, so there is no sign confusion.
Sale season is where percentage math earns its keep. A "percent off" calculation is two steps: first find the discount amount with X% of Y, then subtract it from the original price. A £120 jacket at 25% off: 25% of £120 is £30, so you pay £90.
Watch out for the classic trap: two successive discounts do not add. A 20% discount followed by another 20% is not 40% off — it is 36% off, because the second discount applies to the already-reduced price (0.80 × 0.80 = 0.64). The calculator handles each step, but knowing the trap keeps shop "bargains" honest.
Students meet percentages as grades: 45 marks out of 60 is (45 ÷ 60) × 100 = 75%. The same pattern covers exam scores, quiz results and coursework weightings. If different sections carry different weights, convert each to a percentage first, then combine them according to the weighting — never average raw marks from sections with different totals.
Yes — and it is not a trick. A percentage over 100% simply means "more than the whole of the original". If your savings grow from £100 to £250, that is a 150% increase: the growth alone is one-and-a-half times the starting amount. Percentages above 100% are normal for growth, returns and comparisons — they only look strange when the thing being measured cannot exceed its whole, like a discount (you cannot take more than 100% off a price).
This distinction trips up even newsreaders. If an interest rate rises from 10% to 15%, that is a rise of 5 percentage points — but a 50% relative increase (5 ÷ 10 × 100). "Percentage points" measures the absolute gap between two percentages; "percent" measures the relative change. When someone says "up 5%", always ask: five percent of what?
A 15% tip on a £42 restaurant bill: 0.15 × 42 = £6.30. A shop advertises "7% off everything": on a £200 television that is £14 off, so £186 to pay. Your phone battery drops from 80% to 20%: that is a 75% decrease in charge ((20 − 80) ÷ 80 × 100 = −75%). Once the three formulas are familiar, these stop being calculations and start being reflexes.
Divide the percentage by 100, then multiply by the number. For example, 20% of 150 is 0.20 × 150 = 30. The "X% of Y" mode on this page does that arithmetic for you instantly.
Divide the first number by the second and multiply by 100. For example: 30 is what percent of 150? 30 ÷ 150 × 100 = 20%.
Subtract the old value from the new value, divide by the old value, and multiply by 100. A positive answer means a percent increase; a negative answer means a percent decrease. From 80 to 100 is (100 − 80) ÷ 80 × 100 = 25% increase.
Use ((new − old) ÷ old) × 100. Example: a salary from £30,000 to £33,000 is (£3,000 ÷ £30,000) × 100 = 10% increase.
Use the same formula: ((new − old) ÷ old) × 100. Example: £80 down to £60 is (−£20 ÷ £80) × 100 = 25% decrease.
Yes. Over 100% just means "more than the original whole" — for example, growing from £100 to £250 is a 150% increase. It only looks wrong for things that cannot exceed their whole, like discounts.
Percentage points measure the absolute gap between two percentages (10% to 15% is +5 percentage points); percent measures the relative change (that same move is a 50% increase).
Yes — completely free, with no sign-up. Everything runs in your browser and your numbers are never sent anywhere.
Written by the PagalHo Tools Team. This tool applies the three standard percentage formulas shown above, and every worked example on the page can be checked by hand.
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