The Temperature Converter converts between Celsius (°C), Fahrenheit (°F) and Kelvin (K). In India, weather and cooking use Celsius, while many digital thermometers and doctors in clinics still quote body temperature in Fahrenheit (98.6 °F). Science uses Kelvin. This page gives you the exact formulas, a fever chart and useful reference temperatures.
How to use the temperature converter
- Enter a temperature. Negative values are allowed.
- Choose the From scale and the To scale.
- Press Convert, or Swap units to reverse.
Temperature conversion formulas
K = °C + 273.15 °C = K − 273.15
°F = (K − 273.15) × 9/5 + 32
Temperature can’t be converted with a single multiplication factor like length or weight, because the scales have different zero points. The converter applies these formulas directly.
Worked examples
- 37 °C → 37 × 1.8 + 32 = 98.6 °F
- 102 °F → (102 − 32) × 5/9 = 38.9 °C
- 45 °C (a hot day in Rajasthan) → 113 °F
- −18 °C (freezer) → −0.4 °F
- 25 °C → 298.15 K
Body temperature and fever chart
| °C | °F | What it usually means (adult, oral) |
|---|---|---|
| Below 35.0 | Below 95.0 | Hypothermia. Seek medical help. |
| 36.1 – 37.2 | 97.0 – 99.0 | Normal range |
| 37.3 – 38.0 | 99.1 – 100.4 | Slightly raised / low-grade |
| 38.1 – 39.0 | 100.6 – 102.2 | Fever |
| 39.1 – 40.0 | 102.4 – 104.0 | High fever |
| Above 40.0 | Above 104.0 | Very high. Get urgent medical attention. |
Normal temperature varies by person, time of day and measurement site. Rectal and ear readings run higher, armpit readings lower. In infants under 3 months, any temperature of 38 °C (100.4 °F) or more needs a doctor’s attention. This chart is general information, not medical advice.
Reference temperatures
| Reference point | °C | °F | K |
|---|---|---|---|
| Absolute zero | −273.15 | −459.67 | 0 |
| Celsius and Fahrenheit are equal | −40 | −40 | 233.15 |
| Water freezes | 0 | 32 | 273.15 |
| Comfortable AC setting (BEE default) | 24 | 75.2 | 297.15 |
| Normal body temperature | 37 | 98.6 | 310.15 |
| IMD heatwave (plains, max temperature) | 40+ | 104+ | 313.15+ |
| Water boils (sea level) | 100 | 212 | 373.15 |
| Baking a cake | 180 | 356 | 453.15 |
| Pizza oven | 250 | 482 | 523.15 |
Oven temperatures for recipes
US recipes give oven temperatures in °F. Most Indian OTGs and microwave-convection ovens are marked in °C:
| °F | °C (rounded) | Use |
|---|---|---|
| 300 °F | 150 °C | Slow baking, meringues |
| 350 °F | 180 °C | Cakes, most cookies |
| 375 °F | 190 °C | Muffins, pies |
| 400 °F | 200 °C | Roasting vegetables, bread |
| 425 °F | 220 °C | Roasting, pizza in an OTG |
For a fan or convection oven, reduce the stated temperature by about 10–20 °C.
Quick mental conversion
For weather, °F ≈ °C × 2 + 30 is close enough. 30 °C gives about 90 °F (exact: 86 °F). Going the other way, °C ≈ (°F − 30) ÷ 2. Use the exact formula for fever readings, where a degree matters.
A short history
Daniel Gabriel Fahrenheit proposed his scale in 1724. Anders Celsius proposed a 100-degree scale in 1742, originally with 0 as boiling and 100 as freezing, and it was later reversed. Lord Kelvin introduced the absolute scale in 1848. Since 2019, the kelvin has been defined through the Boltzmann constant, and degrees Celsius are defined from kelvins.
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 (1.8) and add 32. For example, 30 °C × 1.8 + 32 = 86 °F.
How do I convert Fahrenheit to Celsius?
Subtract 32 and multiply by 5/9. For example, (100 °F − 32) × 5/9 = 37.8 °C.
Is 99 °F a fever?
Generally no. 99 °F (37.2 °C) is at the upper end of normal for an oral reading. A fever is usually 100.4 °F (38 °C) or higher.
At what temperature are Celsius and Fahrenheit the same?
At −40. −40 °C equals −40 °F.
How do I convert Celsius to Kelvin?
Add 273.15. Room temperature of 25 °C is 298.15 K. Kelvin has no negative values.