Time of Death Calculator — Algor Mortis Estimation
After death, a body gradually cools toward ambient temperature. Enter the current body temperature, ambient temperature and the environment type, and this calculator estimates how many hours have passed and works back to an approximate time of death. This is an educational tool using Newton's Law of Cooling — actual forensic determination requires a trained examiner using Henssge's nomogram and other methods.
°C
°C
°C
Environment
h
min
Estimated time of death: ~22:42 (±1–3 h uncertainty)
- 1
Temperature ratio
(30 − 20) ÷ (37 − 20) = 0.5882Fraction of original cooling range still remaining. - 2
−ln(temperature ratio)
−ln(0.5882) = 0.5306 - 3
Hours since death
0.5306 ÷ 0.0347 = 15.3Cooling constant k = 0.0347 /hr for the selected environment.
How does this calculator work?
Newton's Law of Cooling gives PMI = −ln[(T_body − T_ambient) / (37 − T_ambient)] / k, where k ≈ 0.035 /hr for still air (higher for wind or water). The result has ±1–3 h uncertainty and is an educational estimate only — real forensic work requires trained professionals.
Formula
How this is calculated
Newton's Law of Cooling models a body losing heat as T(t) = T_ambient + (T_initial − T_ambient) × e^(−k·t). Rearranging for elapsed time t gives t = −ln[(T_body − T_ambient) / (T_initial − T_ambient)] / k. The cooling constant k depends strongly on the environment: a nude 70 kg adult in still indoor air cools at roughly k ≈ 0.035 /hr (Henssge, 1988); moving air or immersion in cold water accelerates cooling significantly.
This tool applies the formula directly with four preset k values covering common conditions. The estimated time of death is then the discovery time minus the computed elapsed hours. Uncertainty is typically ±1–3 hours even under ideal conditions because individual variables — body weight, clothing, body position, post-mortem redistribution of heat — are not captured here.
In real forensic investigations, body temperature is only one of several indicators; lividity (livor mortis), rigor mortis, stomach contents, entomology and witness statements are also considered. Never use this tool for any legal, medical or investigative purpose — consult a licensed forensic pathologist.
Frequently asked questions
Algor mortis is the gradual cooling of a body after death toward the surrounding environmental temperature. It follows an exponential decay curve described by Newton's Law of Cooling, and it is one of the three classic postmortem changes (with livor mortis and rigor mortis) used to estimate time of death.
Under controlled conditions with a known ambient temperature and body weight, the Henssge nomogram (which this calculator simplifies) gives an accuracy of roughly ±1–3 hours for deaths within 24 hours. Accuracy decreases sharply beyond 24 hours as the body approaches ambient temperature.
The cooling rate k varies by a factor of roughly 4× between still indoor air and cold water immersion. A body in cold water cools nearly 4 times faster than one in still air, so the same temperature drop implies a much shorter elapsed time. Clothing, body weight, and whether the body was moved also affect the rate.
Also known as
TG we-Calculate Editorial Team. (2026). Time of Death Calculator — Algor Mortis Estimation [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/time-of-death-calculator
TG we-Calculate Editorial Team. "Time of Death Calculator — Algor Mortis Estimation." TG we-Calculate. 2026. https://we-calculate.com/calculator/time-of-death-calculator.
TG we-Calculate Editorial Team, "Time of Death Calculator — Algor Mortis Estimation," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/time-of-death-calculator
@misc{wecalculate_time_of_death_calculator, title = {Time of Death Calculator — Algor Mortis Estimation}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/time-of-death-calculator}}, year = {2026}, note = {TG we-Calculate} }
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