Temperature Converter: Celsius, Fahrenheit, and Kelvin with Health Interpretation
Is 102°F a high fever? What does 39°C mean? Should you be worried? This tool not only converts body temperature between all three measurement scales — it also tells you what the reading means for your health, based on established clinical thresholds.
The Conversion Formulas
°F to °C: (°F − 32) × 5/9
°C to °F: (°C × 9/5) + 32
Kelvin = °C + 273.15
Worked Examples
38.5°C (moderate fever) to °F:
(38.5 × 9/5) + 32 = 69.3 + 32 = 101.3°F
99°F to Celsius:
(99 − 32) × 5/9 = 67 × 0.556 = 37.2°C
Convert your temperature instantly with our Temperature Converter.
Body Temperature Health Ranges
| Celsius | Fahrenheit | Health Status |
|---|
| Below 35°C | Below 95°F | Hypothermia — medical emergency |
| 35.0–36.0°C | 95.0–96.8°F | Below normal |
| 36.1–37.2°C | 97.0–99.0°F | Normal |
| 37.3–37.9°C | 99.1–100.2°F | Low-grade fever |
| 38.0–38.9°C | 100.4–102.0°F | Moderate fever |
| 39.0–40.0°C | 102.2–104.0°F | High fever |
| Above 40°C | Above 104°F | Very high fever — seek medical care |
Understanding Fever
A fever (pyrexia) is a body temperature above 38°C (100.4°F). It is a physiological response — the body raising its temperature to create an environment less hospitable to pathogens. Most fevers are caused by infections (viral or bacterial) and resolve on their own.
- Low-grade fever (37.3–38°C): Common with viral illness, vaccinations, mild infections. Often does not require medication.
- Moderate fever (38–39°C): Most common range for influenza and bacterial infections. Can be managed with paracetamol or ibuprofen if causing discomfort.
- High fever (39–40°C): Warrants monitoring. See a doctor if it persists more than 48 hours, especially in children under 3.
- Very high fever (above 40°C / 104°F): Medical emergency. Risk of febrile convulsions in young children. Seek emergency care.
Important Measurement Notes
Measurement site matters. Rectal temperature is most accurate (+0.5°C versus oral). Oral is standard for adults. Axillary (armpit) reads 0.5°C lower than oral. Ear thermometers are fast but less reliable.
Normal temperature varies. It is not fixed at 37°C — it varies throughout the day (lowest in morning, highest in late afternoon), with age (older adults run slightly lower), and with activity.
Normal for children can be slightly higher — fever thresholds are 38°C rectally for infants under 3 months, warranting immediate medical attention.
Final Thoughts
Knowing what a temperature reading means is just as important as knowing what the number is. This converter gives you both — the converted value and a clear health interpretation.
Convert and interpret any body temperature with our free Temperature Converter.
Always consult a healthcare professional for medical decisions, especially for fevers in infants, young children, or immunocompromised individuals.