How to Calculate Percentages
The word "percentage" comes from the Latin per centum, meaning "by the hundred". It is simply a ratio expressed as a fraction of 100. Whether you are trying to calculate a 20% discount on a commercial invoice, or figuring out your body fat percentage increase over the holidays, our Percentage Calculator handles the heavy lifting instantly.
Finding X% of Y
This is the most common real-world percentage problem. For instance, what is 15% of £250? To solve this manually, you convert the percentage into a decimal by dividing by 100 (15 / 100 = 0.15). You then multiply the base number by this decimal (250 × 0.15 = 37.5).
Finding what percentage one number is of another
If you scored 45 marks out of a possible 60 on an exam, what is your percentage grade?
The mathematical approach is to divide the part by the whole to get a decimal (45 ÷ 60 = 0.75). You then multiply by 100 to shift the decimal point two places to the right, yielding 75%.
Calculating Percentage Increase or Decrease
Percentage difference (or sequence change) is heavily used in finance, stock market tracking, and science to measure growth or decay over time.
- Step 1: Find the absolute difference between the two values (New Value - Old Value).
- Step 2: Divide that difference by the Old Value.
- Step 3: Multiply the final decimal by 100.
If your rent increased from £1,200 to £1,350, the difference is £150. Dividing 150 by 1,200 gives 0.125. Multiply by 100, and it shows your rent suffered a 12.5% increase.