How we test our calculators
Every calculator is run against worked examples with known answers whenever the site changes. These are some of the checks. Rounding follows the display rules on each page.
| Tool | Input | Expected result |
|---|---|---|
| Temperature | 100 °C | 212 °F · 373.15 K |
| Length | 1 inch | 2.54 cm exactly |
| Length | 1 mile | 1.609344 km exactly |
| Weight | 1 kg | 2.2046226 lb |
| Baking | 1 US cup | 48 teaspoons · 236.588 mL |
| Fuel economy | 30 mpg (US) | 7.8405 L/100 km |
| Mortgage | 350,000 price, 70,000 down, 5.5%, 30 years | 1,589.81 a month · 292,331 interest |
| Loan | 200,000, 4.5%, 25 years | 1,111.66 a month · 133,499.49 interest |
| Auto loan | 30,000, 5,000 down, 2,000 trade-in, 6%, 60 months | 444.65 a month |
| Compound interest | 10,000, 7%, 20 years, 100 a month | 92,480 |
| VAT | 100 at 20% | 120.00 including VAT |
| Discount | 20% off 45 | 36.00 |
| Salary converter | 25 an hour, 40 hours, 52 weeks | 52,000 a year |
| BMI | 70 kg, 175 cm | 22.9 (normal weight) |
| TDEE | male, 30, 70 kg, 175 cm, lightly active | BMR 1,649 · TDEE 2,267 kcal |
| Body fat (Navy) | male 180 cm, neck 38, waist 90 | 19.8% |
| Pregnancy due date | last period 1 Jan 2026 | 8 October 2026 |
| Day of week | 1 January 2000 | Saturday |
| Age | born 15 Jun 1990, at 30 Sep 2026 | 36 years, 3 months, 15 days |
| Paint | 4 × 5 m room, 2.5 m walls, 1 door, 1 window, 2 coats | 7.0 L (7.7 L with 10% allowance) |
| Tile | 4 × 3 m room, 30 cm tiles, 10% waste | 148 tiles |
| Tyre size | 225/65R17 to 235/45R18 | −7.7% · 60 mph reads as 55.4 mph |
| Roman numerals | 1994 | MCMXCIV |
| Number base | 255 decimal | 11111111 binary · FF hex |
| Ring size | US 6 | UK L · EU 52 · 16.51 mm |
| Spain salary | 40,000 gross | 7,739 tax · 2,540 social security · 29,722 net |
Corrections
Pregnancy Due Date: dates could be one day early for visitors west of UTC. Fixed.