How to use the Percentage Calculator
Step 1: Choose what you want to calculate from the options at the top.
Step 2: Enter the two numbers. The labels change to match the calculation you picked.
Step 3: Read the result and the plain-English sentence underneath it.
Step 4: Switch to another calculation without losing what you typed in the first.
Step 5: Press Copy result, or Clear to reset the current calculation.
Features and benefits
Five calculations
Percentage of a number, increase, decrease, difference, and add or subtract a percentage.
Plain-English answers
Each result comes with a sentence such as From 50 to 75 is a 50% increase.
Handles negatives and decimals
Works with negative numbers and decimal values.
Division by zero handled
When a result is mathematically undefined, the tool explains why.
Your entries are kept
Each calculation remembers its own inputs while you switch between them.
The formulas behind each calculation
Percentage of a number: multiply the number by the percentage and divide by 100. Percentage change: subtract the original value from the new value, divide by the original value and multiply by 100; a positive result is an increase and a negative one is a decrease. Add or subtract a percentage: multiply the number by the percentage divided by 100, then add or subtract that amount.
Percentage change versus percentage difference
Percentage change compares a new value with an original one and depends on the order: going from 50 to 75 is a 50 percent increase, but going from 75 to 50 is a 33.3 percent decrease. Percentage difference compares two values that have no obvious starting point, using their average as the base, so the order does not matter: 50 and 75 differ by 40 percent either way.
Common mistakes to avoid
A rise of 50 percent followed by a fall of 50 percent does not return you to the start, because the second percentage applies to a larger number. Also remember the difference between percent and percentage points: if an interest rate moves from 4 percent to 5 percent, it rises by 1 percentage point, which is a 25 percent increase. When the original value is zero, a percentage change cannot be calculated, and the tool will tell you so.
Example use cases
Price changes
Find out how much a price rose or fell in percentage terms.
Exam scores and grades
Work out what percentage a score is of the total.
Business reports
Calculate growth between two periods.
Everyday maths
Tips, taxes, interest and shares of a total.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 15 percent of 200 is 200 times 15 divided by 100, which is 30.
How do I calculate percentage increase?
Subtract the old value from the new value, divide by the old value and multiply by 100.
What is the difference between percentage change and percentage difference?
Change compares a new value with an original and depends on the order. Difference uses the average of the two values as the base, so the order does not matter.
Why can't I calculate a change from zero?
Dividing by zero is undefined, so a percentage change from a starting value of zero cannot be expressed.
Can I use negative numbers?
Yes. The tool accepts negative values for the calculations where they make sense.
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Useful guides
- How to Calculate Profit Margin (and Why It Isn't Markup)Understand profit, profit margin and markup with simple formulas and worked examples, learn how to set a price for a target margin and avoid common pricing mistakes.
- How to Calculate GST in India: Formulas and ExamplesLearn how to add GST to a price and remove it from a GST-inclusive total, with worked examples, the CGST, SGST and IGST split and the mistakes to avoid.
Last updated 7 November 2026.