Fever chart (adults and children over 3 months)
| Reading (°F) | Reading (°C) | Classification |
|---|---|---|
| 97.0–99.0°F | 36.1–37.2°C | Normal |
| 99.1–100.3°F | 37.3–37.9°C | Elevated / low-grade |
| 100.4–102.2°F | 38.0–39.0°C | Fever |
| 102.3–104.0°F | 39.1–40.0°C | High fever |
| Above 104.0°F | Above 40.0°C | Very high - seek medical advice |
| Above 106.0°F | Above 41.1°C | Medical emergency (hyperpyrexia) |
Babies are different
For infants under 3 months, any rectal temperature of 100.4°F (38°C) or higher is an immediate call-the-doctor situation - do not wait to see how the baby does. For babies 3–24 months, call if the fever reaches 102°F (38.9°C), lasts more than 24 hours, or comes with unusual drowsiness, poor feeding, rash, or trouble breathing.
When adults should seek care
Call a clinician if you have
- A fever above 103°F (39.4°C)
- Any fever lasting more than three days
- Fever with stiff neck, severe headache, chest pain, shortness of breath, confusion, rash, or dehydration
Go to emergency care for a reading above 105°F (40.6°C).
Treating the number itself matters less than comfort: fluids, rest, and - if appropriate for you - acetaminophen or ibuprofen. Avoid aspirin for anyone under 18. This page is general information, not medical advice; when in doubt, call your doctor or local health line.
Taking a temperature that you can trust
Fever decisions ride on half a degree, so measurement technique matters:
- Under 3 months: rectal readings only - they are the standard every threshold in this chart assumes for infants.
- 3 months to 4 years: rectal or temporal (forehead); ear thermometers work from about 6 months if positioned well.
- 4 years and up: oral works once a child can hold the probe under the tongue with a closed mouth.
- Adults: any method, but stay consistent and wait 15 minutes after eating, drinking or exercise for oral readings.
Whichever method you use, our normal body temperature guide shows how each one reads relative to oral. Tracking the tiny morning-to-morning shifts of the menstrual cycle is a different job again; see how basal temperature tracking works.
Three fever myths worth dropping
- “The higher the fever, the sicker the child.” Not reliably. A miserable child at 101°F needs more attention than a playful one at 102.5°F. Behavior beats the number, except at the emergency thresholds.
- “Fevers cause brain damage.” Ordinary fevers do not; the body caps them around 105-106°F. The dangerous territory is heat stroke, an external overheating problem, not illness fever.
- “Teething causes real fevers.” Teething can nudge temperature up slightly, but anything at or above 100.4°F (38°C) should be treated as illness, not teeth.
Measurement method comes before chart interpretation
A temperature number is only useful when the measurement site and device are known. Oral, ear, forehead, rectal and underarm readings are not interchangeable, and technique can move a result. Record the number, time, method and symptoms instead of silently “correcting” one method to another with a fixed offset.
If a reading is unexpected, check the device instructions and repeat it correctly. Recent exercise, a hot bath, heavy clothing and the timing of fever-reducing medicine can affect interpretation. A trend measured the same way is often more useful than several readings taken with different devices.
Age and symptoms determine urgency, not the chart color by itself. Guidance for young infants differs from guidance for older children and adults. Seek professional advice for the age-specific threshold, or sooner for breathing trouble, confusion, seizure, severe dehydration or another concerning symptom. This page is a reference for discussing a reading, not a diagnosis.
Keep the thermometer clean and stored as its manufacturer directs. Replace damaged covers or weak batteries, and do not use a device outside its stated measurement site or range. One repeatable method is more useful than many inconsistent readings.