Percentage Calculator
Percent of, percent change, discounts, margin and markup, each with the formula shown.
- Calculated in your browser
- Formula and rounding
- Reviewed
Percentage changeExample
+25.00%
Formula(100 − 80) ÷ 80 × 100 = +25.00%
- Difference
- 20.00
Percentage change
(B − A) / |A| × 100A = 80B = 100
= 25
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Estimates for general information only — not financial, tax or legal advice. Your actual figures depend on your employer’s payroll, your full tax situation, your lender’s or bank’s terms and rules we may not model. Check official sources and speak to a qualified adviser before making decisions. Disclaimer · Report an error
How to calculate a percentage, percent change or discount
Percentages turn up everywhere money does: pay rises, sale prices, price rises, profit and tax. Most of the questions boil down to a few patterns. This calculator has a mode for each one, so you pick the question and fill in the numbers.
Every answer comes with the formula it used. You can check the working, or reuse it in a spreadsheet.
- 1
Pick the question
Choose a mode: percent of, what percent, percent change, add or subtract, reverse, discount, or margin and markup.
- 2
Enter your numbers
Fill in the two or three values the mode asks for. For stacked discounts, add each discount in the order it applies.
- 3
Read the answer and the formula
The result appears as you type, with the formula underneath. Change any number and everything updates.
What this calculator does
- Find X% of any number
- Find what percent one number is of another
- Percent change from one value to another
- Add or subtract a percentage
- Reverse percentage: the original before an increase
- Stacked discounts combined into one total
- Margin and markup from cost and price
- The formula used shown with every result
A price rise, a double discount and a profit check
Three everyday questions
- Percent change: a price goes from 80 to 100. (100 − 80) ÷ 80 × 100 = +25.00%.
- Stacked discount: 20% off, then a further 10% off. 100 × 0.80 × 0.90 = 72.00, a total discount of 28%, not 30%.
- Margin and markup: cost 60, price 100. Profit is 40. Margin is 40 ÷ 100 = 40.00%; markup is 40 ÷ 60 = 66.67%.
The same 40 of profit gives two very different percentages. That’s why margin and markup get mixed up so often.
The formulas behind each mode
- X% of Y:
Y × X ÷ 100 - X is what percent of Y:
X ÷ Y × 100 - Percent change from A to B:
(B − A) ÷ A × 100 - Add X%:
Y × (1 + X ÷ 100); subtract X%:Y × (1 − X ÷ 100) - Original before an X% increase:
Y ÷ (1 + X ÷ 100) - Margin:
(price − cost) ÷ price; markup:(price − cost) ÷ cost
Percent change divides by the starting value, so a change from zero is undefined. The calculator says so rather than showing infinity. More detail is on the methodology page.
Margin vs markup
Both compare profit with something, but not the same thing. Margin compares profit with the selling price. Markup compares it with the cost. Margin can never reach 100%, while markup has no ceiling. A 50% markup gives a margin of only 33.33%.
Price quotes often hide tax as well. To split VAT or sales tax out of a price, use the VAT calculator. To compare a bank’s exchange rate with the reference rate, the currency converter shows the margin in money.
Reverse percentages
If a price of 120 includes a 20% increase, the original was 120 ÷ 1.20 = 100. Taking 20% off 120 gives 96, which is wrong. The increase was 20% of the smaller, original number. The same trap catches pay rises. Pair this with the salary to hourly calculator to see a raise as an hourly figure.
Good to know
- Percent change from zero is undefined, because there’s nothing to divide by. You’ll see a message instead of a number.
- Stacked discounts multiply, they don’t add. 20% then 10% off is 28% in total.
- A rise of 25% followed by a fall of 25% doesn’t bring you back to the start: 80 → 100 → 75.
- A change in a rate, such as interest moving from 4% to 5%, is 1 percentage point but a 25% increase.
What happens to the numbers you type
Your numbers stay in your browser. MoneyOtter works out your results on your device. We don’t send the amounts you type to our servers or store them. If you allow analytics, we record only broad ranges (for example “middle tax band”) to understand how the calculators are used. Like any website with ads, this page also loads advertising scripts; see our Privacy Policy.
The calculator is plain code running in this tab. It makes no network requests with your figures, and nothing is saved when you leave unless you choose to keep it. Read the privacy policy for how ads and analytics work on this site.
Related calculators and guides
Questions people ask
How do I calculate percentage change?
Subtract the old value from the new one, divide by the old value and multiply by 100. From 80 to 100 that’s 20 ÷ 80 × 100 = 25%.
Why don’t 20% and 10% discounts add up to 30%?
The second discount applies to the already reduced price. 100 becomes 80, then 72, so the total discount is 28%.
What’s the difference between margin and markup?
Margin is profit as a share of the selling price; markup is profit as a share of the cost. Cost 60 and price 100 give a 40% margin and a 66.67% markup.
What is the percent change from zero?
It’s undefined. Percent change divides by the starting value, and you can’t divide by zero. The calculator shows a message instead.
How do I find the original price before a percentage increase?
Divide by 1 plus the percentage as a decimal. A price of 120 after a 20% rise was 120 ÷ 1.20 = 100 before it.
What’s the difference between percent and percentage points?
Percentage points measure the gap between two percentages. A rate going from 4% to 5% rises by 1 percentage point, which is a 25% increase in the rate.
How do I work out what percent one number is of another?
Divide the part by the whole and multiply by 100. 30 out of 120 is 30 ÷ 120 × 100 = 25%.
Sources and review
Estimates for general information only — not financial, tax or legal advice. Your actual figures depend on your employer’s payroll, your full tax situation, your lender’s or bank’s terms and rules we may not model. Check official sources and speak to a qualified adviser before making decisions.
Page reviewed by the MoneyOtter team · Methodology · Changelog · Report an error