A percentage calculator that shows the working.
15% of 200 is 30
These numbers are an example. Type over them.
The working
- Turn the percentage into a decimal15 ÷ 100= 0.15
- Multiply by the number0.15 × 200= 30
15% of 200 is 30
Type two numbers and the answer appears with every step of the working, so you can check it by hand. It all happens in your browser; nothing you type is sent anywhere.
How do you work out a percentage of a number?
Divide the percentage by 100 to turn it into a decimal, then multiply by the number. For 15% of 200: 15 ÷ 100 = 0.15, then 0.15 × 200 = 30.
How do you work out what percentage one number is of another?
Divide the part by the whole, then multiply by 100. For 30 out of 200: 30 ÷ 200 = 0.15, then 0.15 × 100 = 15, so 30 is 15% of 200.
How do you work out a percentage change?
Take the starting number from the new one, divide by the starting number, then multiply by 100. From 80 to 100: 100 − 80 = 20, 20 ÷ 80 = 0.25, 0.25 × 100 = 25, a 25% increase.
The starting number matters. Going back from 100 to 80 is a 20% decrease, not 25%, because the 20 is now divided by 100. A change from 0 has no percentage, because the sum would divide by 0. In every mode, an answer with more than 2 decimal places is rounded to 2, marked ≈ and called “about”; the working keeps the longer figure. An answer that would round to 0 is given to 3 significant figures instead.
How do you add or take off a percentage?
Work out the percentage of the number first, then add it or take it away. For 20% off 80: 20 ÷ 100 = 0.2, 0.2 × 80 = 16, then 80 − 16 = 64. To add 10% to 200: 10 ÷ 100 = 0.1, 0.1 × 200 = 20, then 200 + 20 = 220.
The % key on the main calculator does the same in one sum: 200 + 10% gives 220. For a 10% tip worked into a longer sum, see splitting a bill step by step. For GST, use the GST calculator, and for halves, thirds and quarters the fraction calculator.
How do you reverse a percentage?
Divide by the number the change multiplied the original by. A price after 20% off is 0.8 of the original, so a sale price of $64 was 64 ÷ 0.8 = 80. A price after 10% was added is 1.1 of the original, so $220 was 220 ÷ 1.1 = 200. Taking 10% off $220 gives $198, not $200, because the 10% that was added was 10% of $200, not of $220. The main calculator does either division.