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percentage calculator

Work out any
percentage, instantly.

No sign-up, no ads blocking the number. Pick the kind of problem you have below.

X% of Y
X is what %
% change
Increase / decrease
What is % of ?
Result
30
20%
is what percent of ?
Result
20%
20%
Change from to
Percentage change
+20%
an increase
%
New value
172.5

How percentage calculations work

A percentage is just a fraction of 100 — "20%" means 20 out of every 100. The four boxes above cover the situations that come up most often, but they all reduce to the same core relationship: part = percent × whole.

To find X% of Y, convert the percent to a decimal (divide by 100) and multiply: 20% of 150 is 0.20 × 150 = 30. To go the other way — figuring out what percent one number is of another — divide the part by the whole and multiply by 100: 30 ÷ 150 × 100 = 20%.

Example: A shirt costs $150 and there's a 20% sale.
Discount = 0.20 × 150 = $30
Sale price = 150 − 30 = $120

Percentage change (the "% change" tab) is different from a simple percentage — it measures how much a number moved relative to where it started: (new − old) ÷ old × 100. This is why going from 100 to 150 is a 50% increase, but going back from 150 to 100 is only a 33.3% decrease — the base number changed.

What's the difference between a percentage and a percentage point?

A percentage point is a raw difference between two percentages. If interest rates go from 5% to 7%, that's a 2 percentage point increase — but a 40% increase in relative terms (2 ÷ 5 × 100). Financial news often uses these interchangeably, which causes confusion.

Why isn't a 50% increase followed by a 50% decrease back to the original number?

Because each percentage is calculated from a different base. $100 increased by 50% is $150. But $150 decreased by 50% is $75, not $100 — the second calculation is 50% of a bigger number. This is the most common source of percentage confusion.

How do I find the original price before a discount was applied?

Use the "X is what % of Y" logic in reverse: if a discounted price of $80 reflects a 20% markdown, the discounted price is 80% of the original. Divide $80 by 0.80 to get the original price of $100.

Can percentages be negative or over 100%?

Yes. A percentage over 100% just means the part is larger than the whole (200% of 10 is 20). A negative percentage change means a decrease — this calculator's "% change" tab shows a minus sign automatically when a value has gone down.

How do I calculate a tip or a sales tax using percentages?

Both work the same way as "X% of Y" — a 15% tip on a $40 bill is 0.15 × 40 = $6. For sales tax, add the result to the original amount: $40 + $6 = $46 total. If you're specifically calculating a tip, the dedicated Tip Calculator also splits the bill between people.