Temperature converter

Unit converters

Convert Celsius, Fahrenheit and Kelvin.

Updated May 17, 2026

Convert temperature

ValueUnit

In every scale

Unit	Value	Copy
Celsius °C	100
Fahrenheit °F	212
Kelvin K	373.15
Rankine °R	671.67

Quick start

How to convert temperature

Type a value, pick the source scale, read every other scale in the result table.

Step 1

Type the temperature

Enter the value and pick its unit. Switching the unit dropdown converts the displayed value so its meaning is preserved.
Step 2

Read all scales

Celsius, Fahrenheit, Kelvin and Rankine update live in the table. The source unit row is highlighted.
Step 3

Copy a value

Hit Copy on any row to grab that scale's value. Values below absolute zero trigger a physics warning.

In-depth guide

Temperature converter — Celsius, Fahrenheit, Kelvin, Rankine

Convert between the four common temperature scales. Type a value, pick the source unit, and see every other scale update in the table — with a warning if your input falls below absolute zero.

Conversion formulas

From	To	Formula
°C	°F	°F = °C × 9/5 + 32
°F	°C	°C = (°F − 32) × 5/9
°C	K	K = °C + 273.15
K	°R	°R = K × 9/5
°F	°R	°R = °F + 459.67

Common reference points

Reference	°C	°F	K
Absolute zero	−273.15	−459.67	0
Water freezes	0	32	273.15
Room temperature	20	68	293.15
Human body	37	98.6	310.15
Water boils (1 atm)	100	212	373.15
Surface of the sun	5505	9941	5778

Which scale is used where

Celsius — daily life in most of the world, scientific work everywhere.
Fahrenheit — daily life in the United States. Cooking ovens, weather, thermostats.
Kelvin — physics, astronomy, lighting (colour temperature in K). Always positive.
Rankine — US thermodynamics, HVAC and aerospace engineering. Same degree size as Fahrenheit, zero at absolute zero.

Frequently asked questions

Why does the tool warn me about absolute zero?

Temperature has a physical floor at 0 Kelvin (−273.15 °C, −459.67 °F, 0 °R). Values below it are unphysical, so we flag them rather than silently converting nonsense.

What's the difference between Celsius and Kelvin?

Both have the same degree size; Kelvin's zero is shifted to absolute zero. To convert: K = C + 273.15. Scientists prefer Kelvin because it makes physical equations cleaner (no negative temperatures).

When would I ever use Rankine?

American mechanical engineering — thermodynamics tables, gas turbine performance, heating/cooling calculations in HVAC. Rankine is to Fahrenheit what Kelvin is to Celsius: same degree size, zero at absolute zero.

Is the result rounded?

Yes — to 6 decimal places. JavaScript numbers are IEEE-754 doubles, so the underlying conversion is exact for these magnitudes; rounding only affects display.

Why does picking a different source unit keep my value?

When you switch the source unit dropdown we convert the displayed value to the new unit so the meaning is preserved — pick Celsius with 100, switch to Fahrenheit, and you'll see 212 (the same temperature, just relabelled).

Does this work offline?

Yes. All math runs in your browser. Once the page is loaded you can convert in airplane mode.

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