Fever Temperature Calculator

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

Temperature Classification (Adults)

Most clinical definitions put fever at 38.0°C (100.4°F) or higher. The band just below it is a raised temperature rather than a fever, which is why the page starts calling it a fever at 38.0.

Hypothermia starts below 35°C, not just below the normal range. A reading of 35.5°C is usually a cold room, a reading taken after a cold drink, or an armpit or forehead thermometer, and the first step is to check it again. A real core temperature below 35°C needs warming and medical help, and below 32°C it is an emergency.

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.
A temperature below 36°C is a warning sign at this age too. Young babies with a serious infection often run cold rather than hot.

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 39.4°C (103°F) or above, lasts more than 3 days, or is accompanied by severe symptoms.

Older adults: the fever response weakens with age. For older people in care, the Infectious Diseases Society of America counts a single oral reading above 37.8°C (100°F), repeated readings above 37.2°C (99°F), or a rise of 1.1°C (2°F) over the person’s usual temperature as a fever.

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.