Question 1

How do I calculate X% of a number?

Accepted Answer

Divide the percentage by 100, then multiply by the number. For example, 20% of 500 = (20 ÷ 100) × 500 = 100.

Question 2

What is 20% of 200?

Accepted Answer

20% of 200 = 40. Calculation: (20 ÷ 100) × 200 = 40. Use the calculator above to find any percentage of any number instantly.

Question 3

How do I work out what percentage one number is of another?

Accepted Answer

Divide the first number by the second, then multiply by 100. For example, 75 out of 300 = (75 ÷ 300) × 100 = 25%.

Question 4

How do I calculate percentage increase or decrease?

Accepted Answer

Subtract the original value from the new value, divide by the original value, then multiply by 100. For example, from 80 to 100: (100 − 80) ÷ 80 × 100 = 25% increase.

Question 5

What is the difference between percentage change and percentage difference?

Accepted Answer

Percentage change measures how much a value has moved from a starting point — it has a direction (increase or decrease). Percentage difference compares two values without a defined starting point, using the average of both as the base. Use percentage change for before/after comparisons; use percentage difference when neither value is the "original".

Question 6

How do I add a percentage to a number?

Accepted Answer

Multiply the number by (1 + percentage ÷ 100). For example, 200 + 20% = 200 × 1.20 = 240. To subtract a percentage, multiply by (1 − percentage ÷ 100) instead.

Question 7

How do I calculate a percentage on a basic calculator?

Accepted Answer

Most calculators have a % button. To find 15% of 80: type 80 × 15 % and the answer (12) appears. Without a % button: type 80 × 0.15 = 12. To add 15% to 80: type 80 × 1.15 = 92.

Question 8

What is 15% of 60?

Accepted Answer

15% of 60 = 9. Calculation: (15 ÷ 100) × 60 = 9. A quick mental shortcut: 10% of 60 is 6, and 5% is half of that (3), so 15% = 6 + 3 = 9.

Question 9

How do I find the original price before a discount or percentage increase?

Accepted Answer

To reverse a discount, divide the sale price by (1 minus the discount as a decimal). For example, if something is 20% off and costs £64, the original price was £64 ÷ 0.80 = £80. To reverse an increase, divide by (1 plus the increase as a decimal): a price that rose 25% to reach £100 was originally £100 ÷ 1.25 = £80.

Question 10

How do I calculate the VAT included in a price?

Accepted Answer

To extract VAT from a VAT-inclusive total at 20%, multiply by 1/6 (or divide by 6). So a £120 total includes £20 VAT, and the ex-VAT price is £100. The formula: VAT = total × (rate ÷ (100 + rate)). At 20%: total × 20 ÷ 120 = total ÷ 6.

Question 11

What percentage is 3 out of 20?

Accepted Answer

3 out of 20 = 15%. Calculation: (3 ÷ 20) × 100 = 15%. Quick mental check: 1 out of 20 = 5%, so 3 out of 20 = 3 × 5% = 15%.

Question 12

How do I work out my percentage score on a test?

Accepted Answer

Divide your marks by the total marks available, then multiply by 100. For example, 36 out of 45 = (36 ÷ 45) × 100 = 80%. If the paper has weighted sections, calculate each section separately before combining.

Question 13

How do I calculate a percentage of a percentage?

Accepted Answer

Multiply the two percentages together and divide by 100. Example: 20% of 30% = (20 × 30) ÷ 100 = 6%. This matters for stacked discounts: 10% off followed by a further 25% off is not 35% off — the effective reduction is 1 − (0.90 × 0.75) = 32.5%.

Question 14

What is 12.5% of a number?

Accepted Answer

12.5% = 1/8, so divide by 8. For example, 12.5% of 240 = 240 ÷ 8 = 30. Other useful fractions: 25% = ÷ 4, 33.3% ≈ ÷ 3, 10% = ÷ 10, 5% = ÷ 20, 1% = ÷ 100.

Percentage Calculator UK — % of a Number, Increase & Change