Baby fever chart & checker

Is it a fever, and do you need to call someone? Pick your child's age and thermometer, type the reading, and get the AAP-based answer in one step.

Check a temperature

Child's age

Thermometer

Reading

Days with fever so far My child seems very unwell (limp, hard to wake, struggling to breathe, won't drink)

Enter a reading to see what it means. Thresholds: rectal, ear or forehead 100.4°F (38°C); mouth 100°F (37.8°C); armpit 99°F (37.2°C).

Fever chart by age

Age	Fever is	Call pediatrician today	Get care now
Under 3 months	100.4°F / 38°C rectal	Temperature under 97.5°F (36.4°C)	Any fever, even if baby seems fine
3–6 months	100.4°F / 38°C	Any fever; sooner if 102°F (38.9°C) +	Seems very unwell, trouble breathing
6–24 months	100.4°F / 38°C	104°F (40°C) +, or fever over 24 h with no clear cause	105°F (40.6°C) +, limp, non-fading rash, seizure
2 years +	100.4°F / 38°C	104°F (40°C) +, or fever 3 days +	105°F (40.6°C) +, stiff neck, trouble breathing

Why the “fever line” moves with the thermometer

Your child has one core temperature, but each spot you measure sits a different distance from the core. Pick a method and watch where the fever line lands.

100.4°F

Rectal: fever from 100.4°F (38.0°C). Most accurate for babies and children under 3 (AAP).

Rectal readings sit closest to core temperature. The mouth reads about half a degree F lower, and the armpit about a degree lower still, because skin loses heat to the air. That's why the AAP gives different thresholds, and why you shouldn't “add a degree” to an armpit reading. Just use the right line for the method.

When to call

Call 911 or go to the ER now

Baby under 3 months with 100.4°F (38°C) or higher
Trouble breathing, blue or grey lips
A seizure (first one, or lasting over 5 minutes)
Rash that doesn’t fade under a pressed glass
Stiff neck, very drowsy or hard to wake
No wet diaper in 8 hours, no tears, sunken soft spot

Call your pediatrician today

3–6 months with any fever
Temperature 104°F (40°C) or higher at any age
Fever more than 24 hours in under-2s, or 3 days in older children
Ear pain, painful peeing, or fever that went away and came back
You’re worried: trust your instinct

Usually OK to watch at home

Over 6 months, drinking and peeing normally
Playful or alert once the fever comes down
Mild cold symptoms with a fever under 104°F

General guidance based on AAP, NHS and CDC advice, not a diagnosis. If your gut says something is wrong, call your pediatrician or nurse line. You never need permission to seek care.

Caring for a feverish child at home

Offer fluids often: breast milk or formula for babies, water or diluted juice for toddlers. Ice pops count.
Dress in one light layer. Don't bundle a feverish child to “sweat it out”.
Fever medicine is for comfort, not to hit a number. Acetaminophen works from 2 months with a doctor's okay and ibuprofen from 6 months; dose by weight, never give aspirin, and confirm the dose with your pediatrician or pharmacist.
Skip cold baths and rubbing alcohol. They cause shivering, which raises core temperature.

Questions parents ask

What temperature is a fever in a baby?

A rectal, ear or forehead reading of 100.4°F (38°C) or higher is a fever. By mouth, 100°F (37.8°C). Under the arm, 99°F (37.2°C). These are the AAP thresholds.

When is a fever an emergency in a baby?

Any fever of 100.4°F (38°C) or higher in a baby younger than 3 months needs a doctor right away, even if the baby seems fine. At any age, trouble breathing, a non-fading rash, a seizure, stiff neck, extreme sleepiness or signs of dehydration need urgent care.

Is a high number more dangerous than how my child acts?

For children over 3 months, how your child looks and behaves matters more than the exact number. A child with 103°F who is playing between doses is usually less worrying than a child with 101°F who is limp and hard to wake.

Should I wake my child to give fever medicine?

No. The AAP says fever medicine is for comfort. If your child is sleeping comfortably, let them sleep. Never give aspirin to children. Check doses with your pediatrician or pharmacist.

Can teething cause a fever?

Teething may cause a slightly raised temperature, but not a true fever of 100.4°F or more. If your baby has a fever, look for another cause.

Which thermometer is best?

Digital rectal thermometers are the most accurate under age 3 (AAP). Ear thermometers work from 6 months. Oral readings work from about age 4. Armpit and forehead strips are fine for screening but confirm a fever another way in young babies.