100°F to Celsius
100 °F is 37.8 °C. 100 °F is just under the common fever threshold of 100.4 °F (38 °C).
Convert any temperature
Nearby temperatures
| °F | °C |
|---|---|
| 98 °F | 36.7 °C |
| 99 °F | 37.2 °C |
| 100 °F | 37.8 °C |
| 101 °F | 38.3 °C |
| 102 °F | 38.9 °C |
What this reading means
100.0°F (37.8°C) is slightly elevated but below the fever threshold. The standard cut-off for a fever is 100.4°F (38.0°C). A reading here is sometimes called a 'low-grade' temperature — worth keeping an eye on, resting, and staying hydrated, but not itself a fever by the usual definition.
Measurement method changes the number, too: forehead and ear readings can differ from oral, and rectal readings (used for infants) tend to run a little higher. For the same person, a 0.5–1°F difference between methods is normal.
How to convert °F to °C
The exact formula is °C = (°F − 32) × 5/9. For 100.0°F: (100.0 − 32) × 5/9 = 68.0 × 5/9 = 37.8°C. To go the other way, °F = (°C × 9/5) + 32. A quick mental shortcut for Fahrenheit to Celsius: subtract 30 and halve it — close enough for a rough idea, though not exact.
Frequently asked questions
What is 100 degrees Fahrenheit in Celsius?
100°F equals 37.8°C.
Is 100°F a fever?
Not quite — the common fever threshold is 100.4 °F (38.0 °C).