Fahrenheit readings come from US weather apps, home thermostats, meat thermometers and many medical thermometers sold in America. Anyone used to Celsius needs to subtract and divide to make sense of them — this converter does both, in the right order, and shows the work so you can repeat it on paper.
How to use the Fahrenheit to Celsius converter
- Type the reading in Temperature in Fahrenheit (°F). It can be negative, down to −459.67 °F (absolute zero).
- The result appears in °C, with kelvin and Rankine for the same temperature.
- The As a temperature change row tells you what the number means as a difference — for example, “the oven runs 25 °F hot”.
- Below the steps is a chart from −40 °F to 500 °F, annotated with fever thresholds and USDA cooking temperatures.
The Fahrenheit to Celsius formula
Subtracting 32 measures how far the reading is above the freezing point of water. Multiplying by 5/9 then rescales those Fahrenheit degrees into the larger Celsius degrees. Doing it in the other order — dividing first — is the most common mistake and gives a wrong answer.
Worked example: normal body temperature
Step 1. Subtract 32: 98.6 − 32 = 66.6.
Step 2. Multiply by 5/9: 66.6 × 5 ÷ 9 = 37 °C.
The same steps for a home thermostat set to 72 °F: 72 − 32 = 40, and 40 × 5/9 = 22.22 °C.
Body temperature in Fahrenheit and Celsius
Thermometers sold in the US often default to Fahrenheit, while doctors’ guidance from most other countries is written in Celsius:
| °F | °C | Notes |
|---|---|---|
| 97.0 | 36.11 | Within the normal range for many adults |
| 98.6 | 37.00 | The traditional “normal” figure |
| 99.5 | 37.50 | Slightly raised |
| 100.4 | 38.00 | Fever threshold used by the CDC |
| 101.0 | 38.33 | Fever |
| 102.0 | 38.89 | Fever |
| 103.0 | 39.44 | Fever |
| 104.0 | 40.00 | High fever |
This table is for converting units only. Normal ranges depend on age and on where the temperature is taken (mouth, ear, forehead, armpit). For medical decisions, follow your clinician's or the thermometer maker's guidance.
Weather and indoor temperatures
| °F | °C | What it feels like |
|---|---|---|
| 0 | −17.78 | Bitter cold |
| 32 | 0 | Freezing |
| 50 | 10 | Cool, jacket weather |
| 68 | 20 | Typical room temperature |
| 75 | 23.89 | Warm, pleasant |
| 86 | 30 | Hot |
| 100 | 37.78 | Very hot |
A handy pattern: every 18 °F step is exactly 10 °C, so 50, 68 and 86 °F land on round Celsius numbers.
Safe cooking temperatures
The USDA publishes minimum internal temperatures in Fahrenheit. In Celsius they are:
| Food | °F | °C |
|---|---|---|
| Whole cuts of beef, pork, lamb (with 3-minute rest) | 145 | 62.78 |
| Ground meats | 160 | 71.11 |
| Poultry | 165 | 73.89 |
Thermometers outside the US often round these to 63, 71 and 74 °C.
Why “subtract 30 and halve” only half works
The quick estimate turns 68 °F into 19 °C (exact 20) and 50 °F into 10 °C (exact). But 98.6 °F becomes 34.3 °C — nearly 3 degrees short — and 350 °F becomes 160 °C instead of 176.67 °C. Use it for the weather, not for health or cooking. For the reverse direction, use Celsius to Fahrenheit.
Frequently asked questions
How do you convert Fahrenheit to Celsius?
Subtract 32, then multiply by 5/9 (or divide by 1.8). For 68 °F: 68 − 32 = 36, and 36 ÷ 1.8 = 20 °C. The subtraction must come first.
What is 100 °F in Celsius?
100 °F is 37.78 °C — a little above typical body temperature, and a very hot day if it is the air temperature.
What temperature is a fever in Celsius?
The CDC uses 100.4 °F, which is exactly 38.0 °C, as the threshold for a fever. A reading of 104 °F is 40 °C.
Is 98.6 °F really normal body temperature?
98.6 °F (37 °C) is the traditional average, dating from 19th-century measurements. Normal temperature varies from person to person, by time of day and by where it is measured, and many modern studies find typical readings a few tenths of a degree lower.
What is a quick way to estimate °F to °C?
Subtract 30 and halve the result. It is within about 1 °C for everyday weather between 35 °F and 65 °F, but it drifts for hot or very cold temperatures and should not be used for fevers.