This percentage calculator answers the questions people ask most often: what is 15% of 200, 30 is what percent of 120, and by what percentage did a value go up or down. A fourth box adds or subtracts a percentage, for example a 20% markup or a 20% reduction. Every answer updates as you type and shows the exact working, so you can copy the method as well as the result.
Use it for shop discounts and price rises, exam marks, pay rises, tips, tax, interest rates, statistics and business reports. It works with decimals and negative numbers, and everything is calculated in your browser.
How to use the Percentage Calculator tool
- Pick the box that matches your question: X% of Y, X is what % of Y, increase or decrease, or add or subtract a percentage.
- Type your two numbers. You can use decimals such as 12.5 and thousands separators such as 1,250.
- Read the answer in large type. It updates as you type, so there is no button to press.
- Check the formula line under the answer to see exactly how the result was worked out.
Why use ToolOrca Percentage Calculator
- Four common percentage questions on one page
- Live results as you type
- Formula and working shown for each answer
- Percentage increase and decrease with the difference
- Handles decimals and negative numbers
- Free, private and works on phones
Percentage formulas with worked examples
X% of Y: divide the percentage by 100 and multiply. 15% of 200 = 15 ÷ 100 × 200 = 30.
X is what percent of Y: divide the part by the whole and multiply by 100. 30 out of 120 = 30 ÷ 120 × 100 = 25%.
Percentage change: subtract the old value from the new value, divide by the old value and multiply by 100. From 80 to 100 = (100 − 80) ÷ 80 × 100 = 25% increase. From 100 to 80 = (80 − 100) ÷ 100 × 100 = 20% decrease. The two are not equal because each change is measured from a different starting value.
Add or subtract a percentage: multiply by 1 plus or minus the rate. 250 plus 20% = 250 × 1.2 = 300; 250 minus 20% = 250 × 0.8 = 200.
Percentage points versus percent
When a rate moves from 4% to 5%, it has risen by 1 percentage point but by 25 percent (1 ÷ 4 × 100). News reports about interest rates, taxes and election results often mix the two, so check which one is meant before comparing numbers.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. For example, 20% of 85 is 0.20 × 85 = 17.
How do I work out a percentage increase?
Take the new value minus the old value, divide by the old value and multiply by 100. A price that rises from $40 to $50 has gone up by 10 ÷ 40 × 100 = 25%.
What percent is 45 out of 60?
45 ÷ 60 × 100 = 75%. This is how test scores are usually turned into percentages.
If a price drops 50% and then rises 50%, is it back to the start?
No. $100 minus 50% is $50, and $50 plus 50% is only $75. The rise is calculated on the smaller number, so you end up 25% lower than where you started.
How do I find the original number before a percentage was added?
Divide by 1 plus the rate. If $138 includes a 15% increase, the original was 138 ÷ 1.15 = $120. Our sales tax calculator does this for tax.