CalcKitHow to Use the Percentage Calculator
Percentages are everywhere: discounts, tips, exam marks, salary hikes, tax and interest rates. Yet the three basic percentage questions trip people up surprisingly often. This calculator answers all three instantly, with the working shown so you can double-check.
"What is X% of Y?" โ the discount question. Example: 20% off a 150 bill. The maths is (X รท 100) ร Y. "X is what percent of Y?" โ the marks question. Example: you scored 30 out of 150. The maths is (X รท Y) ร 100. "Percentage change from X to Y" โ the growth question. Example: your salary rose from 100 to 120. The maths is ((Y โ X) รท X) ร 100.
The most common mistake is mixing up the second and third types. "30 is what percent of 150?" (answer: 20%) is not the same as "what is the percent change from 30 to 150?" (answer: +400%). The calculator labels each mode clearly so you always pick the right one.
Two mental-math tricks for daily life: to find 10% of anything, just move the decimal point one place left (10% of 850 = 85). To add X% to a price, multiply by (1 + X/100) โ e.g. adding 15% tip means ร 1.15. For bill-splitting with tips built in, our Tip Calculator is even faster.