Temperature Converter

Convert between all 8 temperature scales instantly, with real-world context, formulas and colour temperature.

Celsius °C

Fahrenheit °F

Kelvin K

Rankine °Ra

Delisle °De

Newton °N

Réaumur °Ré

Rømer °Rø

🌡️

Human Feeling

💧

Water Phase

📌

Nearest Reference

💡

Blackbody Colour

Conversion Formulas

°C → °F°F = °C × 9/5 + 32

°F → °C°C = (°F − 32) × 5/9

°C → KK = °C + 273.15

°C → °Ra°Ra = (°C + 273.15) × 9/5

°C → °De°De = (100 − °C) × 3/2

°C → °N°N = °C × 33/100

°C → °Ré°Ré = °C × 4/5

°C → °Rø°Rø = °C × 21/40 + 7.5

Reference Temperature Table

Reference Point	°C	°F	K

How to use

Type any number into one of the eight scale boxes (Celsius, Fahrenheit, Kelvin, Rankine, Delisle, Newton, Reaumur, Romer).
All other scales update live as you type.
Watch the 3D thermometer and the context cards (feels like, phase, reference, blackbody colour) update.
Tap the copy icon next to any value to copy it to the clipboard.
Open Quick Reference to jump to common temperatures like body heat, freezing, boiling.

Frequently asked questions

How do I convert Celsius to Fahrenheit?

Multiply by 9/5 and add 32. For example, 20 C becomes 68 F. The tool does this for you instantly across all eight scales.

What is Kelvin used for?

Kelvin is the SI base unit of temperature. It starts at absolute zero (no thermal motion) and is used in physics, chemistry, and astronomy. 0 K is -273.15 C.

Why are there eight different temperature scales?

Before the SI system, different scientists in different regions defined their own scales. Celsius, Fahrenheit, and Kelvin are still in everyday use. Rankine, Delisle, Newton, Reaumur, and Romer are mostly historical but still appear in older texts and specialised fields.

Is my data sent anywhere?

No. Every conversion runs locally in your browser. Nothing is uploaded, stored on a server, or logged.

The formulas, and why Fahrenheit feels arbitrary

Celsius to Fahrenheit is F = C x 9/5 + 32; the reverse is C = (F - 32) x 5/9. The offset exists because Fahrenheit zeroed his scale on a brine freezing mixture, while Celsius anchored 0 and 100 to water freezing and boiling at sea level. Kelvin removes the offset entirely: K = C + 273.15, with 0 K as absolute zero, the point where molecular motion stops. Scientists use Kelvin because doubling kelvins genuinely doubles thermal energy; doubling Celsius does not.

Reference points worth knowing cold

-40 is the crossover where both scales agree: -40 C = -40 F.
Body temperature: 37 C = 98.6 F. Fever territory begins around 38 C / 100.4 F.
Comfortable room: 20-22 C = 68-72 F. A 1 C thermostat change is 1.8 F.
Oven work: 180 C = 356 F (recipes round to 350 F), 200 C = 392 F (rounds to 400 F). Fan ovens typically run recipes 20 C lower.
Water: freezes 0 C / 32 F, boils 100 C / 212 F at sea level, but only about 95 C in Denver. Boiling point drops roughly 1 C per 300 m of altitude.

Quick mental approximation

For weather, double the Celsius and add 30: 20 C becomes about 70 F (true value 68). It drifts at extremes but is within 2-3 degrees across the everyday range, which is all a packing decision needs.

Why degree differences convert differently

A subtle trap: converting a temperature and converting a temperature difference are different operations. "The oven is 200 C" becomes 392 F using the full formula with its +32 offset. But "raise the temperature by 20 C" becomes "raise it by 36 F"... intervals scale by 9/5 alone, with no offset, because the offset cancels when two temperatures are subtracted. Weather reports trip over this constantly ("10 degrees warmer" means different things in each scale), and the same logic explains why a 1 C fever rise is the 1.8 F your American relatives describe as nearly two degrees. Kelvin sidesteps it entirely: a kelvin and a Celsius degree are the same size, offset aside.