Calculators
Quick answers for age, money, health and percentages.
Clear, step-by-step answers for everyday sums: ages, percentages, discounts and body mass index.
All Calculators (4)
4 ready to use.
Good to know
- Results are for general information. Check important figures, especially for money, health or official deadlines.
- A percentage change is always measured from the starting value.
- BMI is a screening measure for adults, not a diagnosis.
Which tool do I need?
| If you want to… | Use |
|---|---|
| Find an exact age in years, months and days | Age Calculator |
| Work out a percentage, or a percentage increase or decrease | Percentage Calculator |
| Find a sale price after one or two discounts | Discount Calculator |
| Check adult BMI and the healthy weight range for a height | BMI Calculator |
| Count the days or working days between two dates | Date Difference Calculator |
Questions about Calculators
How do I calculate a percentage of a number?
Multiply the number by the percentage, then divide by 100. For example, 15% of 80 is 80 × 15 ÷ 100 = 12.
How is a percentage change worked out?
Subtract the old value from the new value, divide by the old value, then multiply by 100. For example, a rise from 50 to 65 is (65 − 50) ÷ 50 × 100 = a 30% increase.
How is BMI calculated?
BMI is weight in kilograms divided by height in metres squared. For example, 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) = 22.9. For adults, the World Health Organization treats 18.5 to 24.9 as the normal range.