CONVERTERS
Temperature Converter
Convert between Celsius, Fahrenheit, and Kelvin instantly.
THREE SCALES
Convert temperatures locally
| Celsius → Fahrenheit | °F = °C × 9/5 + 32 |
|---|---|
| Fahrenheit → Celsius | °C = (°F − 32) × 5/9 |
| Celsius ↔ Kelvin | K = °C + 273.15; °C = K − 273.15 |
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Temperature converter guide
Celsius, Fahrenheit, Kelvin — three scales for the same heat, used in different corners of the world and the sciences. This converter translates between all three instantly: type a value in any unit and the others update live, with the exact formulas always in view.
It runs entirely in your browser — no server, no waiting, works offline.
The three scales, briefly
- Celsius (°C) — the everyday scale of most of the world: 0°C is the freezing point of water, 100°C the boiling point. The SI standard.
- Fahrenheit (°F) — used mainly in the United States (and a few territories). 32°F freezes water, 212°F boils it. 0°F was originally the coldest achievable brine temperature.
- Kelvin (K) — the absolute thermodynamic scale, starting at absolute zero (−273.15°C). No negative values; used in physics, engineering, and color temperature. Water freezes at 273.15 K.
The formulas
The conversions are exact and simple:
- °F = °C × 9/5 + 32
- °C = (°F − 32) × 5/9
- K = °C + 273.15
- °C = K − 273.15
Quick mental anchors: 0°C = 32°F, 21°C ≈ 70°F (room temperature), 37°C = 98.6°F (body temperature), and 100°C = 212°F (boiling).
Why Kelvin exists
Kelvin is the SI scale for thermodynamic temperature. It starts at absolute zero, the lowest possible thermodynamic temperature, so physically meaningful temperatures are not negative in kelvin. Temperature ratios can be used in thermodynamic calculations, but a kelvin value is not a universal measure of how much heat an object contains. In games and design, "color temperature" also uses kelvin, but that is a different concept: it describes the colour of white light (warmer orange around 3000 K, cooler blue around 6500 K).
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 and add 32: °F = °C × 9/5 + 32. 21°C → 21 × 1.8 + 32 = 69.8°F.
What is the formula for Fahrenheit to Celsius?
Subtract 32 and multiply by 5/9: °C = (°F − 32) × 5/9. 98.6°F → (98.6 − 32) × 5/9 = 37°C.
What is absolute zero?
Absolute zero is 0 K = −273.15°C = −459.67°F, the lowest possible thermodynamic temperature. It is a limiting point that cannot be reached by a finite sequence of physical cooling steps.
Why does America use Fahrenheit?
Historical inertia — the scale was invented by Daniel Fahrenheit in 1724 and adopted early in the US. The rest of the world moved to Celsius (and SI) later.
Is there a temperature where Celsius and Fahrenheit are equal?
Yes — −40°. At −40 degrees, both scales read the same: −40°C = −40°F.
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