Time of Death Calculator

Estimate post-mortem interval using Henssge's double-exponential body cooling model.

Last reviewed: June 2026

Built and maintained by Shannon Patterson · Last updated June 2026

Rectal Temperature

°C

Ambient Temperature

°C

Body Mass

Cooling Condition Factor Educational approximation only; formal casework uses condition-specific correction tables.

Estimated Post-Mortem Interval

Approximate Time of Death

Model Uncertainty

What this calculator solves

This page estimates a post-mortem interval (PMI) from body cooling, not an exact time of death. It uses rectal temperature, ambient temperature, body mass, and a cooling-condition correction factor to solve the Henssge double-exponential cooling equation numerically. The output should be read as a scenario estimate under the assumptions you entered.

The implemented cooling quotient is Q = (rectal temperature - ambient temperature) / (37.2 - ambient temperature). For ambient temperatures up to 23.2°C, the equation uses Q = 1.25e^Bt - 0.25e^5Bt. For warmer ambient temperatures, it uses the alternate Henssge coefficient form Q = (10/9)e^Bt - (1/9)e^10Bt. In both cases, B is calculated from body mass and the selected condition factor, and the browser solves for time t by bisection.

How to choose the condition factor

The factor is an educational shorthand for thermal conditions. A standard unclothed body in still dry air uses 1.0. Clothing, bedding, or other insulation slows cooling, so the effective factor increases. Wetness, moving air, or water exposure can speed cooling, so the factor decreases. Real investigations use more detailed correction tables and scene notes rather than a short dropdown.

When the result is unreliable

Treat the result as unreliable when the body temperature is at or below ambient temperature, the measured core temperature is still near or above the assumed initial 37.2°C, the environment changed materially, the body was moved between locations, or the scene involved strong radiant heat, water, wind, heavy insulation, decomposition, hypothermia, hyperthermia, or delayed/inaccurate readings. A non-rectal or surface temperature is not a drop-in replacement for the core temperature expected by the model.

Worked examples

Stable indoor room: rectal temperature 28°C, ambient temperature 20°C, body mass 70 kg, and factor 1.0 produces a PMI near 16.0 hours. That does not mean a clock time is proven; it means the entered scenario fits that cooling interval under the model.

More insulation: the same readings with heavy clothing or one to two blankets set to factor 1.4 produce a longer interval near 22.1 hours because insulation slows cooling.

Accelerated cooling: the same readings with wet body or moving air set to factor 0.7 produce a shorter interval near 11.7 hours because cooling is faster.

Frequently Asked Questions

It estimates a post-mortem interval from rectal temperature, ambient temperature, body mass, and a cooling-condition correction factor. It is an educational implementation of body-cooling equations, not a forensic or legal determination.

It is most useful when rectal and ambient temperatures were measured carefully, the body stayed in a reasonably stable thermal environment, and the case is still in the early cooling period. Changing rooms, wind, water, insulation, fever, hypothermia, or decomposition can make the estimate unreliable.

The correction factor approximates how clothing, coverings, wetness, air movement, or water exposure change the effective cooling rate. Clothing and covers usually slow cooling by increasing the effective mass factor, while water or moving air can accelerate cooling.

Only with strong caution. If the body moved through different thermal environments, the single ambient-temperature assumption no longer describes the whole cooling history, so the numerical result should be treated as a rough scenario check rather than an estimate.

Do not treat the output as reliable. The model assumes a measured core temperature, typically rectal temperature, and a known ambient temperature. Inaccurate readings, delayed readings, or substituted surface temperatures can materially change the result.

Model checks and sources

Henssge PMI model checks
Check	Why it matters	How this page handles it
Body warmer than ambient	Cooling equations cannot estimate PMI after the body has equilibrated with the environment.	The calculator returns an indeterminate warning.
Ambient below 37.2°C	The quotient denominator uses the assumed initial body temperature.	Inputs at or above that ambient level are rejected.
Ambient above 23.2°C	The Henssge equation uses a different coefficient set in warmer conditions.	The runtime switches from the 1.25/0.25 form to the 10/9 and 1/9 form.
Scene-condition factor	Clothing, water, wind, and coverings can substantially change cooling.	The dropdown applies a simplified effective-mass factor and labels it as educational.

Henssge PMI model checks

Check

Why it matters

How this page handles it

Body warmer than ambient

Cooling equations cannot estimate PMI after the body has equilibrated with the environment.

The calculator returns an indeterminate warning.

Ambient below 37.2°C

The quotient denominator uses the assumed initial body temperature.

Inputs at or above that ambient level are rejected.

Ambient above 23.2°C

The Henssge equation uses a different coefficient set in warmer conditions.

The runtime switches from the 1.25/0.25 form to the 10/9 and 1/9 form.

Scene-condition factor

Clothing, water, wind, and coverings can substantially change cooling.

The dropdown applies a simplified effective-mass factor and labels it as educational.