Percentage Calculator
Three tools, zero friction. Results update as you type — and we show the working, so you learn the trick too.
1 · What is X% of Y?
2 · X is what percent of Y?
3 · Percent change from X to Y
The 10% shortcut everyone should know
Ten percent of any number is that number with the decimal point moved one place left: 10% of 340 is 34. From there you can build almost anything in your head — 5% is half of that (17), 20% is double (68), 15% is 10% + 5% (51), and 1% is 3.4. Restaurant tip, sale discount, tax estimate: all just combinations of 10%, 5% and 1%. Want this to become automatic? Two minutes a day on our daily puzzle or a 60-second sprint will do it.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply, then divide by 100: 15% of 80 = 80 × 15 ÷ 100 = 12. Or use the 10% shortcut: 10% is 8, 5% is 4, so 15% is 12.
How do I find what percent X is of Y?
Divide the part by the whole and multiply by 100: 30 out of 120 = 30 ÷ 120 × 100 = 25%.
What's the percent change formula?
(New − Old) ÷ Old × 100. From 50 to 65: (65 − 50) ÷ 50 × 100 = +30%. Negative results mean a decrease.