Fahrenheit to Celsius
Convert fahrenheit (°F) to celsius (°C) instantly. Convert oven, body and outdoor temperatures.
Fahrenheit → Celsius
-17.2222
°C
1 °F = -17.2222 °C
Frequently asked questions
Subtract 32 first, then multiply by 5/9 (or divide by 1.8). The order matters — dividing before subtracting gives a badly wrong answer. For 98.6°F: 98.6 minus 32 is 66.6, divided by 1.8 gives 37°C.
Subtract 30 and halve. For 70°F that gives 20°C against an exact 21.1, and for 90°F it gives 30°C against an exact 32.2. The approximation runs a degree or two low at higher temperatures but is entirely serviceable for weather.
Fever is generally taken as 100.4°F, which is 38°C. Normal body temperature is about 98.6°F or 37°C, though it varies through the day and between individuals. In an adult, 103°F (39.4°C) or above warrants medical attention, as does any fever in a very young infant. This is general information rather than medical advice.
Subtract 32, then divide by 1.8
Going from Fahrenheit to Celsius reverses both operations, and the order matters.
°C = (°F − 32) × 5/9
Subtract 32 first, then divide by 1.8. Doing it the other way — dividing first and then subtracting — produces a wrong answer, and it is the most common mistake in this direction.
For 98.6°F: (98.6 − 32) = 66.6, then 66.6 ÷ 1.8 = 37°C. Dividing first would give 54.8 − 32 = 22.8, which is badly wrong.
The reference points
- −40°F = −40°C — the scales cross here
- 0°F = −17.8°C
- 32°F = 0°C — water freezes
- 50°F = 10°C
- 68°F = 20°C
- 72°F = 22.2°C — the American thermostat default
- 98.6°F = 37°C — normal body temperature
- 100.4°F = 38°C — the usual fever threshold
- 212°F = 100°C — water boils
A mental approximation
Subtract 30 and halve. For 70°F: 40 ÷ 2 = 20°C against an exact 21.1. For 90°F: 60 ÷ 2 = 30°C against an exact 32.2.
The approximation runs a degree or two low at higher temperatures but is entirely serviceable for weather.
Where the conversion is needed
American weather and travel content. A forecast of 85°F is 29.4°C — pleasant. One of 105°F is 40.6°C, which is a heat warning.
Fever thresholds in American medical content. The figures worth carrying: fever begins around 100.4°F (38°C), and 103°F (39.4°C) or above in an adult, or any fever in a very young infant, warrants medical attention.
American recipes, where oven temperatures are in Fahrenheit. The standard 350°F is 176.7°C, which on an Indian oven marked in 10-degree increments means 175 or 180.
Equipment specifications from US manufacturers — operating temperature ranges, storage conditions and thermal ratings.
Why Fahrenheit exists
Daniel Fahrenheit set his scale in 1724 using a brine freezing point as zero and approximate human body temperature near 96, later adjusted. The apparently arbitrary values are the residue of those original reference points after the scale was redefined against water's freezing and boiling points.
The practical argument sometimes made for it is that Fahrenheit degrees are smaller, giving finer resolution in the range of ordinary weather without decimals. The counter-argument is that Celsius anchors on water, which is more useful for cooking, science and anything involving freezing.
Only the United States, its territories, and a small number of other places use Fahrenheit for everyday temperature. India, like most of the world, uses Celsius throughout — including in weather reporting, medicine and cooking.