Fever temperatures in Celsius and Fahrenheit
Is 37.8 °C a fever? What is 101 °F in Celsius? A body temperature conversion chart, where a fever starts, and how the thermometer site changes the reading.
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Tool for this job: Temperature Converter
A fever is a temperature of 38.0 °C (100.4 °F) or higher, the threshold most health services use. To convert, °F = °C × 9/5 + 32: 37.0 °C is 98.6 °F, 38.5 °C is 101.3 °F and 39.0 °C is 102.2 °F. The full chart below covers 36.0 to 41.0 °C in steps of 0.1.
Thermometers, medicine leaflets and health advice do not always use the same scale. A parent reading 101 °F on a thermometer bought abroad, or a leaflet that says to seek help above 39 °C, needs a quick conversion. This guide gives the body-temperature range in both scales.
Body temperature chart
| °C | °F | Usually means |
|---|---|---|
| 35.0 | 95.0 | Low: hypothermia threshold |
| 36.5 | 97.7 | Normal |
| 37.0 | 98.6 | Normal |
| 37.5 | 99.5 | Upper normal |
| 38.0 | 100.4 | Fever |
| 38.5 | 101.3 | Fever |
| 39.0 | 102.2 | High fever |
| 40.0 | 104.0 | Very high fever |
| 41.0 | 105.8 | Dangerously high |
For any other value, use the Temperature Converter, which shows Celsius, Fahrenheit and Kelvin side by side.
Full chart: 36.0 to 41.0 °C
Every tenth of a degree, converted with °F = °C × 9/5 + 32 and rounded to one decimal place.
| °C | °F | °C | °F | °C | °F |
|---|---|---|---|---|---|
| 36.0 | 96.8 | 37.7 | 99.9 | 39.4 | 102.9 |
| 36.1 | 97.0 | 37.8 | 100.0 | 39.5 | 103.1 |
| 36.2 | 97.2 | 37.9 | 100.2 | 39.6 | 103.3 |
| 36.3 | 97.3 | 38.0 | 100.4 | 39.7 | 103.5 |
| 36.4 | 97.5 | 38.1 | 100.6 | 39.8 | 103.6 |
| 36.5 | 97.7 | 38.2 | 100.8 | 39.9 | 103.8 |
| 36.6 | 97.9 | 38.3 | 100.9 | 40.0 | 104.0 |
| 36.7 | 98.1 | 38.4 | 101.1 | 40.1 | 104.2 |
| 36.8 | 98.2 | 38.5 | 101.3 | 40.2 | 104.4 |
| 36.9 | 98.4 | 38.6 | 101.5 | 40.3 | 104.5 |
| 37.0 | 98.6 | 38.7 | 101.7 | 40.4 | 104.7 |
| 37.1 | 98.8 | 38.8 | 101.8 | 40.5 | 104.9 |
| 37.2 | 99.0 | 38.9 | 102.0 | 40.6 | 105.1 |
| 37.3 | 99.1 | 39.0 | 102.2 | 40.7 | 105.3 |
| 37.4 | 99.3 | 39.1 | 102.4 | 40.8 | 105.4 |
| 37.5 | 99.5 | 39.2 | 102.6 | 40.9 | 105.6 |
| 37.6 | 99.7 | 39.3 | 102.7 | 41.0 | 105.8 |
Where a fever starts
A temperature of 38.0 °C (100.4 °F) or above is the threshold most health services use for a fever. Normal body temperature is not exactly 37 °C for everyone; it varies from person to person, rises slightly in the evening, and is often a little higher in young children.
The thermometer site matters
- Rectal and ear readings tend to run a little higher than mouth readings.
- Armpit readings tend to run lower, so a normal-looking armpit reading may hide a mild fever.
- Forehead scanners are convenient but more easily affected by sweat, sun and drafts.
Take a second reading if the first seems surprising, and use the same method each time.
The conversion formulas
- °F = °C × 9 ÷ 5 + 32. So 38 × 1.8 = 68.4, plus 32 = 100.4 °F.
- °C = (°F − 32) × 5 ÷ 9. So (102 − 32) = 70, × 5 ÷ 9 = 38.9 °C.
Around body temperature, a quick check: each 1 °C is 1.8 °F, so half a degree Celsius is 0.9 °F.
Reading a thermometer bought abroad
Many digital thermometers can switch between °C and °F, usually by holding the power button for a few seconds while the thermometer is off; the manual will say. If yours cannot, keep a copy of the chart above with it. When writing temperatures down for a doctor, note the scale and the measurement site, such as “38.4 °C, under the tongue, 9 pm”, along with the time and any medicine given, since fever reducers lower the reading for several hours.
When to get medical advice
This page is a conversion aid, not medical advice. Health services generally advise getting help promptly for a fever in a baby under three months, a very high temperature, a fever with a rash that does not fade when pressed, stiff neck, confusion, difficulty breathing, or a fever that lasts several days. Follow the guidance of your local health service and call emergency services if someone seems seriously unwell.
Converting other temperatures
For cooking and oven settings, see recipe conversions and oven temperatures.