Percentage Calculator
Find what percent X is of Y, how much X% of Y is, a value after a percent increase or decrease, and the percent change from A to B — all in one place. Great for discounts and markups. Free, right in your browser.
What percent of Y is X?
What is X% of Y?
X increased/decreased by Y%?
(−5,000)
Percent change from A to B?
🔒 All calculations happen only in your browser.
Four percentage questions, one screen
This tool bundles the <strong>four percentage calculations</strong> you reach for most. Type ① 'what percent is X of Y' turns a relationship into a percentage — like how much of a 250-point total a score of 30 is. Type ② 'what is X% of Y' gives the amount for a share, such as 15% of 80,000 won. Type ③ 'X increased or decreased by Y%' shows a sale price after a 20% discount or a 20% markup. Type ④ 'percent change from A to B' measures growth, such as sales rising from 120 to 150. Every field updates the instant you type, so you can compare cases quickly.
The formulas at a glance
A percentage is just a ratio to a base value, expressed out of 100. 'What percent is X of Y' is <strong>X ÷ Y × 100</strong> (30 ÷ 250 × 100 = 12%). 'X% of Y' is <strong>Y × X ÷ 100</strong> (80,000 × 15 ÷ 100 = 12,000). An increase is <strong>X × (1 + Y ÷ 100)</strong> and a decrease is <strong>X × (1 − Y ÷ 100)</strong>. The change from A to B is <strong>(B − A) ÷ A × 100</strong> (120 → 150 is 25%). The base value always sits in the denominator, and this tool applies these formulas with plain arithmetic only.
Chained discounts don't cancel out
Raising a value by 20% and then cutting it by 20% does <strong>not</strong> return the original, because the second percentage is taken from an already-changed number. 10,000 won up 20% is 12,000; down 20% again is 12,000 × 0.8 = 9,600 — lower than where you started. For back-to-back discounts or markups (including 'extra % off' promotions), apply the increase/decrease step twice, one stage at a time, to get the correct final amount.
Percent vs. percentage point
Moving from 3% to 5% is a <strong>2 percentage-point</strong> rise in absolute terms, but a (5 − 3) ÷ 3 × 100 ≈ <strong>66.7%</strong> increase in relative terms — the same event, described two ways. Type ④ here computes the relative percent change, which differs from the raw gap between two rates. This distinction matters most when the underlying unit is already a percentage, like approval ratings, market share, or interest rates. For the absolute gap, just subtract the two values.
Frequently asked questions
I keep mixing up the percentage formulas — can you summarize?
Just four: <strong>what percent X is of Y = X ÷ Y × 100</strong>, <strong>X% of Y = Y × X ÷ 100</strong>, <strong>X increased by Y% = X × (1 + Y ÷ 100)</strong> (subtract from 1 for a decrease), and <strong>percent change A→B = (B − A) ÷ A × 100</strong>. Remember that the base value always goes in the denominator.
If I add 20% then subtract 20%, do I get the original amount?
No. The second percentage is calculated from the already-changed value, so you don't return to the start. 10,000 up 20% is 12,000; down 20% again is <strong>9,600</strong> — lower than the original. Compute chained changes one step at a time with the increase/decrease type.
What's the difference between percent and percentage point?
Going from 3% to 5% is a <strong>2 percentage-point</strong> rise (the gap between the rates), but a <strong>66.7%</strong> increase as a relative change: (5 − 3) ÷ 3 × 100. Type ④ gives the relative percent change; for percentage points, simply subtract the two values.
Are my inputs sent to a server?
No. Every calculation runs entirely in your browser, and the numbers you enter are never uploaded or stored. There's no install or sign-up, and it works offline.