Fever Defervescence Calculator

About this calculator

Defervescence is the medical term for the decline phase of a fever, the period when body temperature falls back toward the normal 37 °C (98.6 °F) baseline after peaking. By taking two temperature readings a known amount of time apart, this calculator finds the rate of temperature decline in degrees per hour and linearly projects how much longer it should take to reach normal if the fever keeps falling at the same pace.

Parents, caregivers, and nursing staff track defervescence to judge whether a fever is responding as expected after an antipyretic like acetaminophen or ibuprofen, or whether it is following the typical resolution curve of a viral illness. A fever that plateaus or fails to trend downward despite treatment is one of the signals clinicians watch for when deciding whether further evaluation is warranted.

The projection here is a simple linear estimate from two data points, not a clinical prediction — actual fever curves are rarely perfectly linear, and this tool is for educational tracking only, not medical advice.