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Temperature Converter

Celsius, Fahrenheit, Kelvin and Rankine

By Guga — BrowserTools maintainer, Tbilisi, Georgia Updated 2026-09-21
Free Private No uploads
What is Temperature Converter?

Temperature is the one everyday conversion that is not a simple ratio, and the reason is the 32-degree offset baked into the Fahrenheit scale. Every figure here goes through the exact formulas — Fahrenheit is Celsius times nine fifths plus 32, Kelvin is Celsius plus 273.15, Rankine is Kelvin times nine fifths — so the four scales interconvert without drift and minus 40 is the single temperature where Celsius and Fahrenheit agree. Because absolute scales exist, Rankine is included alongside Kelvin for engineering work, and it runs to 671.67 degrees where water boils. The results are trimmed to four decimal places, which is far finer than any thermometer. A reference table converts six landmarks — absolute zero, freezing, room temperature, body temperature, fever threshold and boiling — across all four scales at once.

Convert temperatures between Celsius, Fahrenheit, Kelvin and Rankine with instant results and common reference points like body temperature and boiling points.

Private Temperature Converter In Your Browser

Temperature Converter is processed locally with client-side JavaScript. Your files never touch a server, and there is no queue to wait in.

Step-by-Step

How to use Temperature Converter

1

Enter the reading in the Value box, which opens at 20.

2

Tap a button under From scale to pick the scale the reading is in.

3

Tap a target under To scale, or press the arrow between them to reverse the direction.

4

Check the All scales grid for the other three readings at a glance, and consult the reference table below for landmark temperatures.

Key Capabilities
  • Four scales including Rankine, the Fahrenheit-based absolute scale used in engineering
  • Exact affine conversions, not a lookup table of rounded pairs
  • A landmark table covering absolute zero through boiling point across all four scales
  • Readings trimmed to four decimal places for precision beyond any thermometer's
Common Use Cases
  • A cook translating an oven temperature from a Fahrenheit recipe for a European oven that only shows Celsius.
  • A lab technician recording a control sample's temperature in Kelvin alongside the Celsius reading their instrument displays.
  • A parent checking a child's temperature against the 38 °C fever threshold their clinic quoted.
Clear Answers

Frequently Asked Questions

Why is minus 40 the same in Celsius and Fahrenheit?
It is the one temperature where the two scales' different zero points cancel out. Solve C x 9/5 + 32 = C and you get C = -40 exactly. It is a handy sanity check: if a converted value near that region looks wrong, the arithmetic, not the formula, is at fault.
Is a rise of 20 °C the same as a rise of 20 °F?
No, and this trips people up constantly. A 20 °C rise is 36 °F, because Fahrenheit steps are five ninths the size of a Celsius step. Only the temperature values line up after the offset is applied — differences never do, and 20 °C is 68 °F while a 20 °F rise from 68 °F lands on 88 °F, which is 31.1 °C.
What is Rankine for?
It is the absolute scale built on the Fahrenheit degree, so 0 °R is absolute zero. It shows up in US engineering and thermodynamics wherever a power or heat-flow figure is derived from Fahrenheit measurements: 0 °C works out to 491.67 °R and boiling water to 671.67 °R.
Where does 273.15 come from?
It is the size of a Celsius degree above absolute zero, fixed by definition. Kelvin is simply Celsius shifted up by that constant, and Rankine is Kelvin scaled by nine fifths. Both constants are exact, not measured, which is why the four scales stay consistent however far you chain the conversions.