Fever Temperature Calculator
Classify a body temperature reading as normal, low-grade fever, moderate fever, or high fever.
Supports both Celsius and Fahrenheit, with age-based guidance.
Understanding Body Temperature and Fever
Normal body temperature is often cited as 37°C (98.6°F), but this is an average. A healthy range is typically 36.1°C to 37.2°C (97°F to 99°F). Body temperature also varies throughout the day — it is lowest in the morning and highest in the late afternoon.
Temperature Conversion
Celsius to Fahrenheit: °F = (°C × 9/5) + 32 Fahrenheit to Celsius: °C = (°F − 32) × 5/9
Fever Classification (Adults)
| Temperature | Classification |
|---|---|
| Below 36.1°C (97°F) | Hypothermia (below normal) |
| 36.1°C – 37.2°C (97°F – 99°F) | Normal |
| 37.3°C – 38.0°C (99.1°F – 100.4°F) | Low-grade fever |
| 38.1°C – 39.0°C (100.5°F – 102.2°F) | Moderate fever |
| 39.1°C – 40.0°C (102.3°F – 104.0°F) | High fever |
| Above 40.0°C (104°F) | Very high fever — seek medical attention |
Age-Specific Guidance
Infants (under 3 months): Any temperature of 38.0°C (100.4°F) or higher is a medical emergency. Seek immediate medical attention.
Infants 3–6 months: Consult a doctor for any fever of 38.0°C (100.4°F) or above.
Children 6 months to 2 years: Contact a doctor if fever is above 39°C (102°F) or lasts more than 24 hours.
Children 2+ and Adults: Low-grade fevers often resolve on their own. Seek care if fever is above 39.4°C (103°F), lasts more than 3 days, or is accompanied by severe symptoms.
When to Seek Immediate Help
- Any fever in a baby under 3 months old
- Temperature above 40°C (104°F) in anyone
- Fever with stiff neck, confusion, or rash
- Fever after returning from travel to a tropical region
Disclaimer: This tool is for general information only. Always consult a healthcare professional for medical advice about fever management.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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