How to calculate a percentage
Multiply the number by the percent and divide by 100. For example, 15% of 250 = 250 × 15 ÷ 100 = 37.5.
Sale prices and VAT
The “Value − %” row instantly gives a sale price — a £45 top at 20% off is £36. The “Value + %” row adds a percentage on top, handy for 20% VAT on a net price. To reverse a 20%-off sale and find the original, divide the sale price by 0.8.
Working out a percentage change
To express a rise or fall as a percentage, take the difference, divide by the original value, then multiply by 100. A price moving from £80 to £100 is (100 − 80) ÷ 80 × 100 = a 25% increase; going back from £100 to £80 is a 20% fall — the percentages differ because the starting point changes.
Frequently asked questions
Can I use it for a discount?
Yes — the “Value − %” row gives the price after a discount of that percent.
How do I find the original price before a sale?
Divide the sale price by (1 minus the discount as a decimal). A £36 item at 20% off was £36 ÷ 0.8 = £45 before the reduction.
What’s the difference between a percentage and a percentage point?
A move from 4% to 6% is 2 percentage points, but a 50% increase in the rate. Points measure the gap between two percentages; percentage change measures growth relative to the start.