Body Temperature Scale: What Each Range Means

Human body temperature is not a fixed number — it varies by person, time of day, age, and measurement method. The 37°C / 98.6°F value comes from a 19th-century study by German physician Carl Wunderlich. More recent research suggests the true average is closer to 36.6°C (97.9°F), and it has been slowly declining over the past 150 years.

Below 35°C
95°F
Hypothermia

Body cannot generate enough heat. Shivering stops. Risk of cardiac arrest. Requires emergency treatment.

35–36°C
95–96.8°F
Low — mild hypothermia risk

Can occur in cold environments, after anesthesia, or in elderly individuals. Monitor closely.

36–37.2°C
96.8–99°F
Normal range ✓

Healthy body temperature for adults. Varies naturally throughout the day — lowest in early morning, highest in late afternoon.

37.3–37.9°C
99.1–100.2°F
Low-grade fever

May indicate early infection, inflammation, or post-vaccination response. Usually not dangerous in healthy adults.

38–39°C
100.4–102.2°F
Fever

Immune system actively fighting infection. Antipyretics (paracetamol, ibuprofen) may help. See a doctor if fever persists more than 3 days.

39–40°C
102.2–104°F
High fever

Seek medical attention, especially in children under 3 or adults over 65. Risk of febrile seizures in young children.

Above 40°C
104°F
Dangerous — seek emergency care

Risk of organ damage. Above 41.5°C (106.7°F) can be fatal. Requires immediate medical intervention.

Fever Thresholds: Children vs Adults

What counts as a fever depends on age. Children run hotter than adults on average, and the danger thresholds differ significantly.

Newborns (0–3 months)
Fever: ≥ 38°C (100.4°F)

Any fever in a newborn is a medical emergency. The immune system is not yet mature. Go to the emergency room immediately.

Infants (3–36 months)
Fever: ≥ 38°C (100.4°F)

Febrile seizures are most common in this age group (2–5% of children). A temperature above 39°C warrants a call to the pediatrician.

Children (3–10 years)
Fever: ≥ 38°C (100.4°F)

Fever is normal during infections. Monitor comfort level and hydration. See a doctor if fever exceeds 39.5°C or lasts more than 3 days.

Adults (18–65)
Fever: ≥ 38°C (100.4°F)

Most fevers in healthy adults resolve on their own. Seek care if fever exceeds 40°C, lasts more than 3 days, or is accompanied by stiff neck or rash.

Elderly (65+)
Fever: ≥ 37.8°C (100°F)

Elderly individuals may have serious infections without high fever. Even a modest temperature rise of 1–1.5°C above baseline warrants attention.

Measurement Method Matters: Why Your Thermometer Reading Varies

The same person at the same moment will show different temperatures depending on where you measure. This is why the "normal" value varies across guidelines.

Method Normal range Fever threshold Accuracy
Rectal 36.6–38°C (97.9–100.4°F) ≥ 38°C (100.4°F) Highest — closest to core temp
Oral 35.5–37.5°C (95.9–99.5°F) ≥ 37.8°C (100°F) Good — affected by food/drink
Axillary (armpit) 34.7–37.3°C (94.5–99.1°F) ≥ 37.2°C (99°F) Lowest — ~1°C below core
Tympanic (ear) 35.8–38°C (96.4–100.4°F) ≥ 38°C (100.4°F) Good — technique-sensitive
Temporal (forehead) 36–37.5°C (96.8–99.5°F) ≥ 38°C (100.4°F) Convenient — less accurate

Temperatures Near 37°C — in Fahrenheit

35°C → 95°F 36°C → 96.8°F 37°C → 98.6°F 38°C → 100.4°F 39°C → 102.2°F 40°C → 104°F 41°C → 105.8°F 42°C → 107.6°F

Related Temperature Topics

30°C = 86°F
Hot summer day — heat stress risk
38°C = 100.4°F
Fever threshold — when to act
40°C = 104°F
High fever — seek emergency care
21°C = 69.8°F
Ideal indoor room temperature

Frequently Asked Questions

What is 37 degrees Celsius in Fahrenheit?
37°C equals 98.6°F. This is calculated using the formula: °F = (37 × 9/5) + 32 = 98.6°F. It is the classic reference value for normal human body temperature, established by Carl Wunderlich in 1851.
Is 37°C a normal body temperature?
Yes, 37°C (98.6°F) is within the normal range. However, "normal" varies between 36.1°C (97°F) and 37.2°C (99°F) depending on the person, time of day, and measurement method. A 2020 Stanford study found the average American body temperature has dropped to about 36.6°C (97.9°F) over the past 150 years.
Is 37°C a fever?
No. 37°C (98.6°F) is not a fever. Most medical guidelines define fever as a temperature of 38°C (100.4°F) or higher. Temperatures between 37.3°C and 37.9°C may be described as a low-grade fever by some clinicians, but 37°C itself is squarely within the normal range.
Why is 98.6°F considered normal body temperature?
The 98.6°F (37°C) standard comes from German physician Carl Wunderlich, who measured axillary (armpit) temperatures in thousands of patients in the 1850s and calculated this average. Modern studies suggest the actual average is slightly lower — around 97.9°F (36.6°C) — and that body temperature has been declining over time, possibly due to reduced chronic inflammation in modern populations.
At what temperature should I go to the hospital?
Adults should seek emergency care for temperatures above 40°C (104°F) or any fever accompanied by severe headache, stiff neck, confusion, or difficulty breathing. For newborns under 3 months, any fever of 38°C (100.4°F) or higher is an emergency.
How do I convert 37°C to Fahrenheit?
Use the formula: °F = (°C × 9/5) + 32. For 37°C: (37 × 9/5) + 32 = 66.6 + 32 = 98.6°F. Or use the converter at the top of this page for any temperature instantly.