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Fever temperature guide: °F, °C and what it means

100.4°F (38.0°C) is the standard threshold for a fever in most clinical guidelines. Here's the complete range — from normal to when it's time to seek medical advice — in both °F and °C.

100.4°Ffever threshold

38.0°Cfever threshold

98.6°Faverage normal

Temperature ranges: °F, °C and what they mean

°F	°C	Category	General guidance
95.0°F	35.0°C	Below normal	—
97.0–99.0°F	36.1–37.2°C	Normal range	—
99.1–100.3°F	37.3–37.9°C	Elevated / low-grade	Watch, rest, fluids
100.4–102.2°F	38.0–39.0°C	Fever	Rest, fluids, monitor
102.3–104.0°F	39.1–40.0°C	High fever	Consider medical advice, especially if it persists
104.1°F+	40.1°C+	Very high fever	Seek medical attention promptly

These are widely used clinical conventions, not a diagnosis. "Normal" body temperature itself varies by person, age, time of day, and how it's measured (oral, ear, forehead, and rectal readings all differ slightly). A single number rarely tells the full story — how someone feels, other symptoms, and how long a fever lasts usually matter more than the exact reading.

Why this is more useful than a plain converter

A calculator can tell you that 103°F is 39.4°C. It can't tell you that 39.4°C falls in the "high fever" range, or that persistent high fevers are generally worth discussing with a doctor. That context is the point of this page.

Every common fever reading, converted

°F	°C
99°F	37.2°C
100°F	37.8°C
100.4°F	38.0°C
101°F	38.3°C
102°F	38.9°C
103°F	39.4°C
104°F	40.0°C
105°F	40.6°C
106°F	41.1°C

Frequently asked questions

What temperature is considered a fever?

100.4°F (38.0°C) or above is the standard clinical threshold used by most health guidelines.

What is a high fever?

Generally, 102.3°F (39.1°C) and above is considered a high fever. Readings of 104°F (40°C) or higher are considered very high and worth prompt medical attention.

Is 99°F a fever?

No — 99°F (37.2°C) is within or just above the normal range for most people, not typically classed as a fever.

Should I see a doctor for a fever?

This page gives general information, not medical advice. If a fever is very high, persistent, or accompanied by concerning symptoms, contact a healthcare professional.