How do you calculate a percent of a number?

Change the percent to a decimal by dividing by 100, then multiply. For 18% of 250: 0.18 × 250 = 45.

How do you work out what percent one number is of another?

Divide the part by the whole and multiply by 100. 27 out of 30 is 27 ÷ 30 = 0.9, which is 90%.

What is the easiest way to find a percent in your head?

Find 10% by dividing by 10, then build from it. For 30% of 70, 10% is 7, so 30% is 3 × 7 = 21.

How do you find the original number from a percent?

Divide the part by the percent to find 1%, then multiply by 100. If 25% of a number is 30, then 1% is 1.2 and 100% is 120. Or notice that 25% is a quarter, so the whole is 4 × 30 = 120.

Is 20% of 50 the same as 50% of 20?

Yes, both are 10. A percent of one number always equals that number percent of the other, which can turn a hard question into an easy one.

What grade learns percentages?

In the US, percent starts in grade 6 (6.RP.A.3.c), with percent increase, decrease, tax and tips in grade 7 (7.RP.A.3). In England, Year 5 introduces per cent and Year 6 calculates percentages of amounts.

Is there a free percentages worksheet with answers?

Yes. Use the Print a worksheet button on this page. Each worksheet is freshly made, and the answer key can show answers only or answers with worked steps.

Grades 6 and 7 (Years 6 to 8 in England)

Percentages: how to find a percent of a number

Here is how to calculate percentages: finding a percent of a number, writing one number as a percent of another, and working back to the whole. Try the free percent practice below, then print a fresh percentages worksheet with an answer key.

The method, step by step

Write the percent as a fraction out of 100 or as a decimal: 35% = 35/100 = 0.35.
Multiply the number by that fraction or decimal.
To work it out in your head instead, find 10% by dividing by 10, and 1% by dividing by 100.
Build the percent you need from those pieces, such as 35% = 10% + 10% + 10% + 5%.
Check the size: a percent under 100% must give an answer smaller than the number you started with.

CCSS 6.RP.A.3.CCCSS 7.RP.A.3England: Y6 Ratio and proportionEngland: KS3 NumberEngland: GCSE Foundation RatioEngland: GCSE Foundation Number

Worked example

What is 35% of 240?

Per cent means out of 100, so 35% = 35/100.
10% of 240 is 240 ÷ 10 = 24.
30% is three lots of 10%: 3 × 24 = 72.
5% is half of 10%: 24 ÷ 2 = 12.
35% = 30% + 5%, so 72 + 12 = 84.
Check with the decimal: 0.35 × 240 = 84. So 35% of 240 is 84.

Practice now

Question 1 of 100 correct

A download is 35% complete. So far 56 MB have downloaded. How big is the whole file, in MB?

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What a percent means

Per cent means per hundred. 35% means 35 out of every 100, so it is the fraction 35/100 and the decimal 0.35. That is what makes percentages so handy for comparing: every amount becomes a share of the same 100.

Picture a bar split into 10 equal parts. Each part is 10% of the bar. If the whole bar stands for 240, each part is worth 24, three parts are worth 72, and the whole bar, 100%, is 240. A hundred square works the same way: shade 35 of the 100 small squares and you have shaded 35% of it.

How to calculate percentages: three kinds of question

Almost every percent question is one of three types. Each uses the same three numbers: the part, the whole and the percent. Spot which one is missing and you know what to do.

Percent of a number (the part is missing): 20% of 150 = 0.2 × 150 = 30.
What percent (the percent is missing): 18 out of 24 is 18 ÷ 24 = 0.75, which is 75%.
Finding the whole (the whole is missing): 40% of a number is 80. Then 10% is 80 ÷ 4 = 20, so 100% is 20 × 10 = 200.

A quick check catches most slips. 20% is one fifth, so 30 should be a fifth of 150, and it is, because 30 × 5 = 150.

Percent of a number in your head

A few benchmark percents make mental math quick. Learn these and you can build almost any whole-number percent.

50%: halve it. 50% of 86 is 43.
25%: halve it, then halve again. 25% of 360 is 90.
10%: divide by 10. 10% of 470 is 47.
5%: half of 10%. 5% of 470 is 23.5.
1%: divide by 100. 1% of 470 is 4.7.
Put them together: 15% of 80 is 8 + 4 = 12, and 75% of 80 is 60.

Percents also swap round. 8% of 50 is the same as 50% of 8, which is 4. When one order looks hard, try the other.

Percent increase and decrease

To increase an amount by a percent, find the percent and add it on. To decrease it, take it away. A $60 jacket with 25% off: 25% of 60 is 15, so the sale price is 60 − 15 = $45. A quicker way is a multiplier: 25% off leaves 75%, and 0.75 × 60 = 45.

To find a percent change, divide the change by the original amount. A club that grows from 400 to 480 members has grown by 80, and 80 ÷ 400 = 0.2, which is a 20% increase. Always divide by the starting amount, not the new one.

How it is taught in school

In the US, Common Core introduces percent in grade 6 as a rate per 100: finding a percent of a quantity, and finding the whole when you know a part and the percent (6.RP.A.3.c). Grade 7 uses percents in multistep problems such as tax, tips, markups and markdowns, simple interest, and percent increase and decrease (7.RP.A.3).

In England, Year 5 pupils learn that per cent means parts per hundred and write percentages as fractions and decimals. Year 6 pupils calculate percentages of amounts, such as 15% of 360, and use percentages to compare. Percentage increase, decrease and original value problems are part of Key Stage 3.

How parents can help

Make sure fractions out of 100 feel easy first. If 3/4 = 75/100 makes sense, 75% will too.
Use sale signs in shops. Ask what 30% off a $40 item saves, then what the new price is.
Practice 10% and 50% of everyday numbers until they are automatic. They are the building blocks for everything else.
Ask for an estimate first: is 35% of 240 more or less than half? Roughly a third?
Keep sessions short. Print a fresh worksheet, let your child mark it with the answer key, and go through the worked steps for any they missed.

Common mistakes

Putting the numbers the wrong way round. 12 out of 48 is 12 ÷ 48 = 0.25, or 25%. Working out 48 ÷ 12 = 4 answers a different question.
Treating 5% as the number 5. 15% of 60 is 6 + 3 = 9, because 5% is half of 10%, not 6 + 5 = 11.
Moving the decimal point the wrong way. 7% is 0.07, not 0.7, which is 70%.
Stopping one step early. For a 20% discount on $50, the saving is $10, but if the question asks for the sale price, the answer is $40.
Dividing by the new amount in a percent change. A rise from 50 to 60 is 10 ÷ 50 = 20%, not 10 ÷ 60.
Thinking a 50% rise followed by a 50% fall gets you back to the start. 100 up 50% is 150, and 150 down 50% is 75.

Questions people ask

How do you calculate a percent of a number?: Change the percent to a decimal by dividing by 100, then multiply. For 18% of 250: 0.18 × 250 = 45.
How do you work out what percent one number is of another?: Divide the part by the whole and multiply by 100. 27 out of 30 is 27 ÷ 30 = 0.9, which is 90%.
What is the easiest way to find a percent in your head?: Find 10% by dividing by 10, then build from it. For 30% of 70, 10% is 7, so 30% is 3 × 7 = 21.
How do you find the original number from a percent?: Divide the part by the percent to find 1%, then multiply by 100. If 25% of a number is 30, then 1% is 1.2 and 100% is 120. Or notice that 25% is a quarter, so the whole is 4 × 30 = 120.
Is 20% of 50 the same as 50% of 20?: Yes, both are 10. A percent of one number always equals that number percent of the other, which can turn a hard question into an easy one.
What grade learns percentages?: In the US, percent starts in grade 6 (6.RP.A.3.c), with percent increase, decrease, tax and tips in grade 7 (7.RP.A.3). In England, Year 5 introduces per cent and Year 6 calculates percentages of amounts.
Is there a free percentages worksheet with answers?: Yes. Use the Print a worksheet button on this page. Each worksheet is freshly made, and the answer key can show answers only or answers with worked steps.

Updated November 1, 2026.

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