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ToolBoxGenie

Temperature Converter

Converters · Added 9 August 2026

Convert a temperature between Celsius, Fahrenheit, Kelvin and Rankine — with the exact formula shown next to every result, so you can check the working.

Result

1 °C in fahrenheit

33.8 °F

°F = (°C × 9/5) + 32

The same value in every unit

Celsius (°C)
1
Fahrenheit (°F)
33.8
Kelvin (K)
274.15
Rankine (°R)
493.47

Temperature scales differ in where zero sits as well as in step size, so these are offset conversions rather than simple multiplications.

How to use the temperature converter

  1. 1Type the temperature in the Value box. Negative numbers are fine — enter −40 as -40.
  2. 2Select the scale it is in and the scale you want. The formula being applied appears directly under the answer.
  3. 3The panel below lists the same temperature on all four scales at once.
  4. 4Swap units reverses the conversion, which is handy for checking that a figure round-trips as you expect.

Examples

A warm day

Input
30 °C
Result
86 °F

The quick mental version — double it and add 30 — gives 90 °F. Close enough for deciding on a jacket, wrong for an oven.

Oven temperature from a US recipe

Input
350 °F
Result
176.666667 °C

Most ovens are set to the nearest 10, so this is the familiar 175 °C or gas mark 4.

Absolute zero

Input
0 K
Result
−273.15 °C

Nothing can be colder. A negative Kelvin figure always means an input error somewhere.

About the temperature converter

Three scales, three different reference points

Celsius pins its scale to water: 0 for freezing and 100 for boiling at sea-level pressure. Fahrenheit's original reference points were a brine freezing mixture and human body temperature, which is why its numbers look arbitrary — water freezes at 32 and boils at 212.

Kelvin abandons reference substances entirely and starts at absolute zero, the point at which molecular motion is minimal. Because it shares Celsius's step size, scientific work can move between the two by adding or subtracting 273.15 and nothing else.

Reference points worth memorising

A handful of anchors makes it possible to sanity-check any conversion at a glance. Water freezes at 0 °C / 32 °F and boils at 100 °C / 212 °F. Normal body temperature is about 37 °C / 98.6 °F. A comfortable room is 20–22 °C or 68–72 °F. A hot summer day is 35 °C / 95 °F.

The rough mental conversion — double the Celsius figure and add 30 — is accurate to within a few degrees across normal weather temperatures, and drifts badly outside that range. For oven temperatures, medical readings or anything technical, use the exact formula.

Frequently asked questions

What is the formula for Celsius to Fahrenheit?
°F = (°C × 9/5) + 32. The 9/5 accounts for Fahrenheit degrees being smaller — there are 180 of them between freezing and boiling against Celsius's 100 — and the +32 shifts the zero point, because water freezes at 32 °F rather than 0 °F.
Is there a temperature where Celsius and Fahrenheit agree?
Yes, exactly one: −40. Minus forty degrees Celsius is minus forty degrees Fahrenheit. It is the single point where the two scales cross, and a quick way to sanity-check any conversion tool.
Why does Kelvin not use a degree symbol?
Kelvin is an absolute scale measured from absolute zero, so a kelvin is a unit of temperature in its own right rather than a position on a scale. It is written 300 K, not 300 °K. Its steps are the same size as Celsius steps, which is why converting between the two is just an offset of 273.15.
What is Rankine used for?
Rankine is to Fahrenheit what Kelvin is to Celsius: an absolute scale starting at absolute zero but stepping in Fahrenheit-sized degrees. It appears in some US engineering and thermodynamics work and almost nowhere else.
Why can I not just multiply to convert temperatures?
Because temperature scales have different zero points as well as different step sizes. Length units all agree that zero means no length, so a single factor works. Zero Celsius and zero Fahrenheit are different physical temperatures, so every conversion needs a shift as well as a scaling.