Percentage Calculator
Solve common percentage math.
Percentage Inputs
Part divided by whole gives the percentage.
Percentage Summary
Percentage Calculator Overview
A general-purpose Percentage Calculator handles the most common percentage problems people run into finding what percentage one number is of another, finding a percentage of a number, and calculating percentage increase or decrease between two values.
Why Use This Calculator
- Handles multiple percentage calculation types in one tool
- Great for shopping discounts, grades, and financial math
- Instant, accurate results with no manual formulas
- Works for both increases and decreases
Common Formulas
Ratio: (X ÷ Y) × 100
Value: (X ÷ 100) × Y
Change: [(New − Old) ÷ Old] × 100
Worked example: percentage increase and reverse percentage
Use the percentage calculator for percentage-of, increase, decrease, and reverse-percentage problems.
- 1Subtract the old value from the new value to find the change.
- 2Divide the change by the original value.
- 3Multiply by 100 to express the result as a percentage.
- 4For a reverse percentage, divide by the remaining percentage after the change.
The percentage calculator is for general mathematical relationships, while marks percentage is designed for obtained marks and total exam marks.
General percentage calculations
Use this tool for everyday percentage, discount, increase, decrease, and reverse-percentage problems.
Common mistakes to avoid
- Do not confuse percentage points with percent change.
- Use the original value as the base when calculating percentage increase or decrease.
Frequently Asked Questions
What's the difference between percentage increase and percentage points?
A percentage increase is relative (e.g., going from 10% to 15% is a 50% increase), while a percentage point difference is absolute (a 5 percentage point increase). These are commonly confused.
Can percentage be negative?
Yes a negative result in a percentage change calculation indicates a decrease rather than an increase.
How do I calculate a percentage discount?
Use 'What is X% of Y' to find the discount amount, then subtract it from the original price, or use the increase/decrease formula with the discounted price as the 'new value.'
Why do my manual calculations sometimes differ slightly from the tool?
Usually due to rounding try carrying more decimal places in manual calculations for an exact match.
How do I calculate a reverse percentage, like finding the original price before a discount?
Divide the discounted price by (1 − discount rate as a decimal). For example, if $76 is the price after a 5% discount, the original price = 76 ÷ 0.95 = $80.
What is percentage error and how is it calculated?
Percentage error measures how far an estimated or measured value is from the true value: [(|Estimated − Actual|) ÷ Actual] × 100. It's commonly used in science and engineering to express measurement accuracy.
How do I convert a fraction to a percentage?
Divide the numerator by the denominator, then multiply by 100. For example, 3/4 = 0.75, and 0.75 × 100 = 75%.
Can I calculate discounts?
Yes. Use percentage-of for the discount amount or reverse percentage to find the original price.
What is the difference between percentage and percentage points?
A percentage is relative to a base value, while percentage points describe an absolute movement between two percentages.
Calculator content author
Written by Abubakar
Grade Calculation Analyst & Founder of Grade Average Calculator
Abubakar is a grade calculation analyst and the founder of Grade Average Calculator. He manages the entire website, from building each calculator to testing and reviewing its results for accuracy.