What is X% of Y?
e.g. what is 15% of 200?
What is % of ? = –
X is what percent of Y?
e.g. 30 is what percent of 200?
is what percent of ? = –
Percentage change
e.g. from 50 to 75, what's the change?
From to is a –
Find the whole
e.g. 30 is 15% of what number?
is % of = –
How each one works
- X% of Y — multiply Y by X, then divide by 100. 15% of 200 is (15 × 200) ÷ 100 = 30.
- X is what percent of Y — divide X by Y, then multiply by 100. 30 out of 200 is (30 ÷ 200) × 100 = 15%.
- Percentage change — subtract the original from the new value, divide by the original, then multiply by 100. From 50 to 75 is ((75 − 50) ÷ 50) × 100 = 50% increase.
- Find the whole — divide the known part by the percentage as a decimal. If 30 is 15% of a number, the number is 30 ÷ 0.15 = 200.
Common questions
What is the formula for percentage change?
Subtract the original value from the new value, divide by the absolute value of the original, then multiply by 100. A positive result is an increase and a negative result is a decrease.
Why is percentage change based on the original number?
Because a change is always relative to where you started. Going from 50 to 75 is a 50% increase, but going from 75 back down to 50 is a 33.3% decrease, not 50%, since the starting point is different each time.
Is my data saved anywhere?
No. Every calculation runs in your browser and nothing is sent anywhere or stored.