What is a temperature converter?
A temperature converter translates between Celsius (°C), Fahrenheit (°F), and Kelvin (K) — the three scales used worldwide. India / most of the world uses Celsius; the US uses Fahrenheit; scientists and engineers use Kelvin for absolute calculations.
Unlike length or mass, temperature scales don't share a zero point — they use offsets, not just multiplication factors. This is why a simple "factor lookup" doesn't work for temperature.
How temperature conversion works
Three formulas:
°F = °C × 9/5 + 32
°C = (°F − 32) × 5/9
K = °C + 273.15
°C = K − 273.15
The offsets are 32 (between °C and °F) and 273.15 (between °C and K).
Worked example
| Common temperature | °C | °F | K |
|---|---|---|---|
| Body temperature | 37.0 | 98.6 | 310.15 |
| Room temperature | 25 | 77 | 298.15 |
| Water freezing | 0 | 32 | 273.15 |
| Water boiling (sea level) | 100 | 212 | 373.15 |
| Mumbai summer peak | 35 | 95 | 308.15 |
| Antarctica winter | -50 | -58 | 223.15 |
| Absolute zero | -273.15 | -459.67 | 0 |
Mental math shortcuts
| Approximation | Use when |
|---|---|
| °C to °F: double and add 30 | Quick US weather chats (close to actual × 9/5 + 32) |
| °F to °C: subtract 30 and halve | Reverse direction |
| 0°C = 32°F | Freezing reference |
| 20°C ≈ 68°F | Comfortable room temperature |
| 100°C = 212°F | Boiling reference |
| -40°C = -40°F | Both scales agree once |
Why three scales
- Celsius: 0 = water freezes, 100 = water boils (at sea level). Designed for everyday observation.
- Fahrenheit: 32 = water freezes, 212 = water boils. Historical; based on Daniel Fahrenheit's brine + body-temperature reference points.
- Kelvin: 0 = absolute zero (no molecular motion). Used in physics, chemistry, and any calculation involving thermodynamic laws.
Engineers use Rankine (= Fahrenheit + absolute) in some US thermodynamics contexts. Rarely encountered today. CalcMaster doesn't include Rankine.
Practical contexts
| Field | Default unit |
|---|---|
| Indian weather forecast | °C |
| US weather forecast | °F |
| Cooking (recipes worldwide) | °C, °F, or "Gas Mark" (UK) — see Oven Temp |
| Body temperature (clinical) | °C (India), °F (US/UK) |
| Industrial heating | °C |
| Cryogenics / liquid gases | K |
| Climate science | °C (IPCC), Kelvin (researchers) |
| Astronomy | K |
Considerations
- Negative Kelvin doesn't exist physically. Below absolute zero (0 K) is theoretically impossible — molecular motion can't go negative.
- Body temperature varies. Normal range: 36.1-37.2 °C (97.0-99.0 °F). Fever begins around 38°C (100.4°F). Hyperthermia/heat stroke at 40°C+ (104°F+).
- Boiling point varies with altitude. At sea level, water boils at 100°C. At Mumbai sea-level: yes. At Manali (2000 m): ~93°C. At Mt. Everest base camp (5000 m): ~84°C. Recipes adjust accordingly.
- Fahrenheit's relevance is fading. Most countries dropped F decades ago. US is the major holdout; younger Americans increasingly use °C through phones and apps.
Limitations
- The calculator handles °C, °F, K only. Rankine, Réaumur, and Newton scales aren't supported (very rarely used today).
- Doesn't handle temperature differences (delta-T) — but the math is simpler for those: 1°C change = 1.8°F change = 1 K change. Use for engineering rate calculations.
Related calculators
- Oven Temp — adds Gas Mark for UK cooking
- Heat Index — feels-like with humidity
- Wind Chill — feels-like with wind
- Dew Point — humidity-temp relationship
- Energy (Conversion) — joules / kWh / calories
Final note. Temperature scale confusion still causes recipe disasters, weather miscommunications, and the occasional medical error. If a recipe says "350°", check whether it's °C or °F — that 162-degree gap is the difference between "perfect roast chicken" and "burned to charcoal". This calculator removes the doubt in 5 seconds.