Percentage Calculator: Calculate Percentages, Increases, and Decreases Instantly

Calculate any percentage: what is X% of Y, percentage change between two numbers, percentage increase or decrease, and reverse percentage calculations. Multiple modes in one tool.

Mathematical Audit

Percentage Formulas

Four core percentage calculation types, each with its own formula.

What is X% of Y? → Result = (X ÷ 100) × Y
X is what % of Y? → Percentage = (X ÷ Y) × 100
Percentage Change → Change % = ((New − Old) ÷ |Old|) × 100
Increase/Decrease → New Value = Old × (1 ± Change% ÷ 100)

Percentage change is positive for increases and negative for decreases. 'Percent' comes from Latin 'per centum' meaning 'by the hundred.'

Operational Guide

How to Use the Percentage Calculator

1

Select the calculation type

Choose from: X% of Y, X is what % of Y, percentage change, or percentage increase/decrease.

2

Enter your numbers

Fill in the values for your chosen calculation type.

3

Click Calculate

See the result with a full explanation of the calculation.

Real-World Scenario Example

"What is 15% of $85? → (15 ÷ 100) × 85 = $12.75. A $85 restaurant bill with 15% tip = $12.75 tip = $97.75 total."

Inputs

mode:x-percent-of-y
x:15
y:85

Result

$12.75

Important Disclaimer

All calculations use standard mathematical formulas. Results are accurate to floating-point precision. For financial calculations involving percentages, always verify results with your financial institution or advisor.