Degrees Celsius to degrees Fahrenheit converter

How to convert Celsius to Fahrenheit

Multiply the Celsius temperature by 1.8 (which is 9/5), then add 32: °F = °C × 1.8 + 32. For example, 30 °C × 1.8 = 54, and 54 + 32 = 86 °F. The formula works for any reading; for a temperature change, multiply by 1.8 and skip the 32.

Where 1.8 and 32 come from

Degrees Celsius (°C) come from a scale built on water, which freezes at 0 °C and boils at about 100 °C at sea level. Fahrenheit puts those same two points at 32 °F and 212 °F.

So 100 Celsius degrees cover the same range as 180 Fahrenheit degrees, which makes each Celsius degree 1.8 Fahrenheit degrees. The 32 is there because water freezes at 32 °F, not 0. Centigrade is the old name for Celsius and converts the same way.

Worked examples

• 38 °C, the usual fever threshold: 38 × 1.8 = 68.4, and 68.4 + 32 = 100.4 °F.
• 32 °C, a hot summer afternoon: 32 × 1.8 = 57.6, and 57.6 + 32 = 89.6 °F.
• 45 °C: 45 × 1.8 = 81, and 81 + 32 = 113 °F.
• 98 °C, just short of boiling: 98 × 1.8 = 176.4, and 176.4 + 32 = 208.4 °F.
• −10 °C: −10 × 1.8 = −18, and −18 + 32 = 14 °F. A negative reading follows the same order: multiply, then add 32.

Celsius to Fahrenheit chart

−273.15 °C is absolute zero, the lowest temperature possible, so no reading goes below it. At −40 the two scales show the same number, and 37 °C (98.6 °F) is the traditional figure for normal body temperature.

The double-and-add-30 shortcut

To estimate in your head, double the Celsius number and add 30. It is exact at 10 °C (50 °F) and close for weather: 20 °C gives 70 °F, against an exact 68 °F.

The error grows by 1 °F for every 5 °C away from 10 °C, so the shortcut fails in the kitchen: 180 °C comes out as 390 °F, 34 °F hotter than the exact 356 °F.

Oven temperatures

Recipe tables round Celsius oven settings to 25 °F steps: 180 °C (356 °F) becomes 350 °F, 200 °C (392 °F) becomes 400 °F and 220 °C (428 °F) becomes 425 °F.

A UK recipe marked "fan" gives the setting for a fan oven, about 20 °C below the conventional one. For "180 °C fan" in a conventional oven, convert 200 °C and set about 400 °F. The oven temperature converter also handles gas marks.

Temperature changes: multiply by 1.8 only

A change in temperature has no zero point to shift, so skip the 32. A rise of 10 °C is a rise of 18 °F, and the 1.5 °C global-warming target is 2.7 °F of warming.

Adding 32 to a change turns that 1.5 °C into 34.7 °F, a reading just above freezing, not a difference. NIST lists temperature intervals separately from readings for this reason.

Common mistakes

• Adding 32 before multiplying. (30 + 32) × 1.8 gives 111.6 instead of 86 °F.
• Using 5/9 instead of 9/5. That fraction belongs to the reverse formula: 30 × 5/9 + 32 gives 48.7 °F. Above −40, the Fahrenheit number is always the larger one.
• Converting a reading that was already Fahrenheit. 32 °C is a hot day (89.6 °F), while 32 °F is freezing (0 °C). Check the symbol on the source first.

Converting back, or to kelvin

To go from Fahrenheit to Celsius, subtract 32 and divide by 1.8, or use the Fahrenheit to Celsius converter. The Celsius to Kelvin converter adds 273.15 for science work, and the temperature converter covers Rankine and Réaumur.