Temperature Converter
Convert between Celsius (°C), Fahrenheit (°F), and Kelvin (K) instantly. Results update as you type.
All Scales at a Glance
Temperature Conversion Formulas
°C = (°F - 32) × 5/9
K = °C + 273.15
Understanding Temperature Scales
Celsius (°C) — Used by most countries. Water freezes at 0°C and boils at 100°C at standard atmospheric pressure. Named after Swedish astronomer Anders Celsius.
Fahrenheit (°F) — Used primarily in the United States. Water freezes at 32°F and boils at 212°F. Named after German-Polish physicist Daniel Gabriel Fahrenheit.
Kelvin (K) — The SI unit of temperature used in science. Starts at absolute zero (-273.15°C). The degree symbol is not used — it's simply "Kelvin" or "K". Named after Lord Kelvin.
Common Temperature References
| Description | °C | °F | K |
|---|---|---|---|
| Absolute Zero | -273.15 | -459.67 | 0 |
| Water Freezes | 0 | 32 | 273.15 |
| Room Temperature | 20—22 | 68—72 | 293—295 |
| Human Body | 37 | 98.6 | 310.15 |
| Water Boils | 100 | 212 | 373.15 |
| Oven (Baking) | 180 | 356 | 453.15 |
| C and F Equal | -40 | -40 | 233.15 |
Quick Mental Conversion Tips
- °C to °F rough estimate: Double the Celsius value and add 30. Example: 25°C × 50 + 30 = 80°F (actual: 77°F).
- °F to °C rough estimate: Subtract 30, then halve. Example: 80°F — (80-30)/2 = 25°C (actual: 26.7°C).
- Key anchors: 0°C = 32°F, 10°C = 50°F, 20°C = 68°F, 30°C = 86°F, 37°C = 98.6°F, 100°C = 212°F.
Three scales, one physical quantity
Temperature measures the average kinetic energy of particles in a substance. The three scales in active use today are Celsius (°C, the international standard for daily life and most science), Fahrenheit (°F, dominant in the United States), and Kelvin (K, the SI unit, used in physical sciences). Rankine (°R) survives in some US engineering disciplines but is otherwise rare.
The formulas, written out
- °C → °F: F = (C × 9/5) + 32
- °F → °C: C = (F − 32) × 5/9
- °C → K: K = C + 273.15
- K → °C: C = K − 273.15
- °F → K: K = (F − 32) × 5/9 + 273.15
- °R → K: K = R × 5/9
Reference points
| Phenomenon | °C | °F | K |
|---|---|---|---|
| Absolute zero | −273.15 | −459.67 | 0 |
| Water freezes | 0 | 32 | 273.15 |
| Body temperature | 37 | 98.6 | 310.15 |
| Room temperature | 20 | 68 | 293.15 |
| Hot summer day | 35 | 95 | 308.15 |
| Water boils (sea level) | 100 | 212 | 373.15 |
| Oven, hot | 230 | 450 | 503.15 |
| Surface of the Sun | 5,500 | 9,932 | 5,773.15 |
Mental shortcuts
- Quick °C → °F: double the °C and add 30. Within 5°F up to about 30°C. (Exact: ×1.8 + 32.)
- Quick °F → °C: subtract 30 and halve. Same accuracy bounds.
- Two scales meet at −40°. −40°C = −40°F. The only point where Celsius and Fahrenheit read the same number.
- "Add 273" for Kelvin. Close enough for back-of-envelope work; use 273.15 for anything precise.
Why temperature differences are not scale-free
A temperature difference of 10°C equals a difference of 18°F (because the Fahrenheit degree is 5/9 the size of a Celsius degree). But a difference of 10 K equals 10°C exactly — the Kelvin and Celsius degree are the same size; only the zero point differs. This matters in thermodynamic calculations, heat-transfer formulas, and weather "anomaly" reports.