Percentage Calculator

Calculate percentages instantly: what is X% of Y, X as a percent of Y, or percent increase and decrease. Free, clear math with no signup.

Reviewed / updated August 4, 2026

Your inputs

%

Result

15% of 240

36

Percent
15%
Of value
240
Result
36

15% of 240 equals 36.

Suggested next steps

  • Switch to “X is what % of Y?” if you know both amounts and need the percent.
  • Use the Discount Calculator for sale-price math with a percent off.
  • Try % increase/decrease to compare an old value with a new value.

How the percentage calculation works

This tool supports three everyday percentage problems:

  1. What is X% of Y? → result = (X ÷ 100) × Y
  2. X is what % of Y? → percent = (X ÷ Y) × 100
  3. Percent change → ((new − old) ÷ |old|) × 100

Pick a mode, enter the two numbers, and the result updates immediately — no submit button. Rule-based tips explain whether a share is large, whether a part exceeds the whole, and how to read increase versus decrease. Charts compare the inputs so you can see relative size at a glance.

Worked example

Mode: What is X% of Y? with X = 15 and Y = 240

  1. 15 ÷ 100 = 0.15
  2. 0.15 × 240 = 36

So 15% of 240 is 36. In “X is what % of Y?” mode, entering 36 and 240 returns 15%. If a price rises from 240 to 276, percent change = (36 ÷ 240) × 100 = 15% increase.

Methodology and notes

All math runs in your browser. Division by zero is blocked for “is what percent” and for percent change from a zero start. For money-specific percent-off problems, the Discount Calculator formats currency and optional sales tax more directly.

Frequently asked questions

How do you calculate a percentage of a number?

Convert the percent to a decimal by dividing by 100, then multiply by the number. Example: 15% of 240 = 0.15 × 240 = 36. This calculator does that as soon as you enter both values.

How do you find what percent one number is of another?

Divide the part by the whole, then multiply by 100. Example: 36 is what percent of 240? (36 ÷ 240) × 100 = 15%. The whole cannot be zero.

How is percent increase or decrease calculated?

Subtract the starting value from the ending value, divide by the absolute value of the starting value, then multiply by 100. Going from 80 to 100 is a 25% increase; from 100 to 80 is a 20% decrease.

Why is doubling a value a 100% increase, not 200%?

Percent change is measured against the starting amount. If you start at 50 and end at 100, you gained 50, which is 100% of the start. A 200% increase would mean ending at three times the start (50 → 150).

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