Temperature °F → °C
Convert temperature from °F to °C
Sources last checked: 2026-11-03
Temperature °F → °C
Convert temperature from °F to °C
Converts units only; reference ranges depend on the laboratory, the assay and the patient.
What is the Temperature °F → °C?
Body temperature is given in degrees Fahrenheit in the USA and in degrees Celsius in Europe, Turkey and in scientific literature. Unlike most unit conversions, this one is not a pure factor: the scales have different zero points, so 32 is subtracted before dividing by 1.8. The definitions follow NIST SP 811 and the SI brochure.
When to use it
- Reading US case reports, textbooks or patient records
- Interpreting home thermometers or devices set to °F
- Entering a temperature into a score or form defined in °C
When not to use it
- Temperature differences (e.g. a change over time): divide the difference by 1.8 without subtracting 32
- Comparing values measured at different body sites as if they were equivalent
How it is calculated
°C = (°F − 32) ÷ 1.8
Clinical pearls and limitations
- Converts units only; reference ranges depend on the laboratory, the assay and the patient.
- Fixed points: 32 °F = 0 °C and 212 °F = 100 °C (freezing and boiling of water at sea level).
- Subtract first, then divide: (°F − 32) ÷ 1.8. Dividing first is the most common mistake.
- Rectal, oral, axillary, tympanic and core measurements give systematically different values; the site and method matter as much as the unit.
- Thresholds for fever or hypothermia depend on the guideline and the measurement site.
Frequently asked questions
How do I convert Fahrenheit to Celsius?
Subtract 32, then divide by 1.8. Example: 98.6 °F → (98.6 − 32) ÷ 1.8 = 37.0 °C; 104 °F → (104 − 32) ÷ 1.8 = 40.0 °C.
Why can't I just multiply by a factor?
Because 0 °F and 0 °C are different temperatures. The scales differ both in step size (1.8) and in zero point (32).
How do I convert a temperature change from °F to °C?
Divide by 1.8 only. A rise of 1.8 °F equals a rise of 1 °C.
Evidence and guidelines
- Primary source: NIST Special Publication 811 (2008), Guide for the Use of the International System of Units — Appendix B.8/B.9 conversion factors: 1 lb = 0.45359237 kg, 1 in = 2.54 cm, 1 mmHg = 133.322 Pa, t/°C = (t/°F − 32)/1.8.
- BIPM. The International System of Units (SI), 9th edition, 2019 — Table 8 (non-SI units accepted for use with the SI, incl. litre) and the definition of the kelvin and degree Celsius.
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<p><a href="https://medelix.ai/en/calculators/fahrenheit-to-celsius">Temperature °F → °C calculator by Medelix</a></p>For healthcare professionals and medical students. These tools support, and do not replace, clinical judgement. Always check results against the original source and your local protocols.