A Fahrenheit to Celsius calculator converts US-style temperatures into the metric scale used almost everywhere else. Enter a value in °F and the calculator returns the °C equivalent using °C = (°F − 32) × 5 ÷ 9.
Useful for sharing US weather forecasts with anyone outside the US, reading metric scientific or medical literature, converting oven temperatures from metric recipes, or just understanding what the news from the rest of the world is actually telling you.
Key takeaway
Fahrenheit and Celsius differ in two ways at once: where they put zero (Fahrenheit's is 32 degrees colder than Celsius's freezing point) and how big each degree is (Fahrenheit degrees are smaller, 1°C = 1.8°F). Converting between them needs both a subtraction (to align zeros) and a multiplication (to rescale the step size).
How it's calculated
The conversion:
°C = (°F − 32) × 5 ÷ 9
The − 32 shifts the Fahrenheit value down so that water's freezing point lands at 0 (where Celsius starts). The × 5/9 (or ÷ 1.8) rescales each Fahrenheit degree into a Celsius degree, there are 9°F per 5°C across the water-freezing-to-boiling span (180°F = 100°C).
Note the order of operations matters: subtract 32 first, then multiply by 5/9. Doing it the other way around (multiplying first then subtracting) gives the wrong answer, try 32°F as a check: (32 − 32) × 5/9 = 0°C ✓, while 32 × 5/9 − 32 ≈ −14.2 ✗.
Source: Standard temperature conversion, °C = (°F − 32) × 5 ÷ 9
Examples
70°F, comfortable indoor temperature
- Temperature 70 °F
70°F converts to 21.1°C, the bottom of the typical comfortable indoor temperature range (most people set thermostats between 68 and 76°F, or 20-24°C). Mental shortcut: 70 − 30 = 40, halved = 20 (close to actual 21).
98.6°F, normal body temperature
- Temperature 98.6 °F
98.6°F is 37°C, the long-cited normal human body temperature (modern research suggests the population average is closer to 36.6°C, but the 37°C reference point is still standard in clinical settings). Above 38°C / 100.4°F is the standard threshold for fever.
Frequently asked questions
How do I convert Fahrenheit to Celsius in my head?
Use the subtract-30-then-halve shortcut: subtract 30 from the Fahrenheit value, then halve it. So 80°F → 50, halved = 25°C (actual: 26.7°C). 50°F → 20, halved = 10°C (actual: 10°C, exactly right). The shortcut is within a few degrees of the real answer across normal weather ranges, plenty accurate for travel planning.
Why is the formula (F − 32) × 5/9, not the other order?
Because you need to shift before you scale. Subtracting 32 first aligns the zero point of Fahrenheit (32°F = 0°C). Multiplying by 5/9 then rescales each Fahrenheit degree into the larger Celsius degree. If you scaled first then subtracted, the offset would be in the wrong "scale", try it with 32°F: the right way gives 0°C, the wrong way gives ~−14°C.
What's the formula in reverse?
Going Celsius back to Fahrenheit, the formula flips: °F = °C × 9/5 + 32. Multiply first by 9/5 (= 1.8) to rescale, then add 32 to shift the zero point into the Fahrenheit position. So 0°C → 0 × 1.8 + 32 = 32°F (water freezing). 100°C → 100 × 1.8 + 32 = 212°F (water boiling).
When do scientists use Celsius vs. Kelvin?
Both are metric, but Kelvin is absolute, its zero is at absolute zero (no thermal motion at all). Celsius's zero is at water's freezing point. The two scales have identical step size, so converting is just an offset: K = °C + 273.15. Scientists use Kelvin for thermodynamics and any physics where ratios matter (a gas at 600 K really is twice as hot as one at 300 K); Celsius is fine for everyday temperatures.