Math Calculators

Percentage Calculator

Solve the three everyday percentage questions: X% of Y, X is what percent of Y, and the percent change between two values.

Quick guide

First choose the question you need answered: a percentage of a number, what percent one number is of another, or the percent change between two values. Then enter the two numbers; check which value is the base, especially for increases and decreases.

Read the full explanation

How It Works

Percentages express a ratio out of 100. The three core questions — percent of a value, a value as a percent, and percent change — cover discounts, tips, tax, grades, and growth.

Formula Used

X% of Y = (X ÷ 100) × Y; X as % of Y = (X ÷ Y) × 100; change = ((new − old) ÷ old) × 100.

Example Calculation

25% of 200 is 50; 45 out of 180 is 25%; a price rising from $80 to $92 is a 15% increase.

Practical Use Cases

Verify store discounts and sale prices.
Work out tips and tax quickly.
Measure growth or decline between two numbers.

Use This Calculator Step by Step

Select the question that matches your task: a percentage of an amount, one amount as a share, or a change from a starting value.
Identify the reference base before entering numbers, especially when comparing increases and decreases.
Keep intermediate precision and round the final result as appropriate for the task.

Check Your Result

A price rising from $80 to $92 increased by 15% because the difference of $12 is divided by $80. Going back from $92 to $80 is a decrease of about 13.04%, because the reference base is now $92.

Assumptions and Limits

A percentage with a zero denominator is undefined; check the inputs instead of treating it as an ordinary zero result.
Percentage points and relative percent change are different measurements. Successive discounts also cannot simply be added.