Temperature Converter

The formulas.

• Celsius to Fahrenheit: °F = °C × 9/5 + 32. Fahrenheit to Celsius: °C = (°F − 32) × 5/9.
• Kelvin: K = °C + 273.15. Kelvin has no degree sign and starts at absolute zero.
• Rankine: °R = °F + 459.67, an absolute scale with Fahrenheit-sized degrees, still used in some US engineering.

The calculator converts your value to Celsius first, then to the other scales. Body temperature of 98.6 °F becomes (98.6 − 32) × 5/9 = 37 °C, 310.15 K and 558.27 °R.

Readings versus differences. A common mistake is converting a temperature change with the full formula. If the weather warms by 10 °C, it has warmed by 18 °F, not 50 °F. Differences only scale, by 9/5 or 5/9, with no offset; and a change of 1 °C equals a change of 1 K. Choose "A temperature difference" for changes, tolerances, climate warming figures and recipe adjustments, and "A temperature reading" for actual temperatures.

Reference points.

• Absolute zero: 0 K, −273.15 °C, −459.67 °F. Nothing can be colder, so the converter rejects anything below it.
• −40 is the same in Celsius and Fahrenheit, the one point where the scales cross.
• Water freezes at 0 °C (32 °F) and boils at 100 °C (212 °F) at sea level. At higher altitudes it boils lower, about 90 °C at 3,000 m.
• Normal body temperature is around 37 °C (98.6 °F), though it varies from about 36.1 to 37.2 °C; a fever is generally 38 °C (100.4 °F) or above.
• Room temperature is around 20–22 °C (68–72 °F).

Quick mental conversions. Double the Celsius figure and add 30 for a rough Fahrenheit: 20 °C gives 70 °F (exact: 68). For Fahrenheit to Celsius, subtract 30 and halve. These are within a few degrees for everyday weather but drift at extremes, so use the exact result for cooking, medicine and science.

Cooking. Oven temperatures in recipes often convert to rounded figures: 180 °C is listed as 350 °F (exactly 356 °F), and 200 °C as 400 °F (exactly 392 °F). Fan ovens usually run about 20 °C lower than conventional settings. UK gas marks are another scale: gas mark 4 is about 180 °C.

Where each scale is used. Celsius is used for weather and daily life almost everywhere. Fahrenheit remains standard in the United States and a few other places. Kelvin is the SI unit for science, used for colour temperature of lights (a 2,700 K warm bulb, 6,500 K daylight) and in physics. Rankine is rare outside US thermodynamics.

History. Daniel Fahrenheit proposed his scale in 1724; Anders Celsius proposed his in 1742, originally with 0 for boiling and 100 for freezing, reversed after his death. Since 2019 the kelvin has been defined from the Boltzmann constant, and Celsius is defined from the kelvin.

Precision. Results are rounded to two decimal places; Kelvin readings from Celsius are exact to the 0.15 offset.

Body temperature in Fahrenheit

Inputs: Temperature: 98.6; From: Fahrenheit (°F); Type: A temperature reading

Enter 98.6, choose Fahrenheit and "A temperature reading". Subtracting 32 and multiplying by 5/9 gives 37 °C, and the absolute scales follow.

Result: 98.6 °F = 37 °C 98.6 °F 310.15 K 558.27 °R For reference: hot day / near body temperature.

A 10-degree rise

Inputs: Temperature: 10; From: Celsius (°C); Type: A temperature difference

Enter 10, choose Celsius and "A temperature difference". Only the 9/5 scale applies, so a 10 °C rise is 18 °F, not 50 °F.

Result: A change of 10 °C equals: 10 °C 18 °F 10 K 18 °R (Differences scale only, no 32° offset.)

Where the scales meet

Inputs: Temperature: -40; From: Celsius (°C); Type: A temperature reading

Enter −40 in Celsius. It converts to −40 °F, the only temperature with the same number on both scales.

Result: -40 °C = -40 °C -40 °F 233.15 K 419.67 °R For reference: at or below water's freezing point.

How do I convert Celsius to Fahrenheit?

Multiply by 9/5 and add 32.

What is 37 °C in Fahrenheit?

98.6 °F.

Is a 10 °C rise 50 °F?

No. A 10 °C change is an 18 °F change.

What is absolute zero?

0 K, −273.15 °C or −459.67 °F.

When are Celsius and Fahrenheit equal?

At −40.

Does it work offline?

Yes, once the page has loaded.