Time Of Death Calculator

Estimate the postmortem interval (hours since death) from rectal and ambient temperature, body weight, and clothing/environment, using Henssge's forensic cooling formula.

Quick Facts

Method
Henssge double-exponential cooling formula
The standard forensic method for early postmortem interval from rectal temperature.
Reliable window
Roughly the first 24-48 hours
Accuracy falls as the body approaches ambient temperature.
Published precision
±2.8 hours (95% CI, best case)
Wider for unusual clothing, environment, or body weight.

Your Results

Calculated
Estimated time since death
-
Postmortem interval (hours)
Estimated time of death
-
Exam time minus the interval
Cooling rate constant
-
Henssge's B, per hour
Confidence interval
-
95% CI on the estimate

Ready

Enter the scene temperature readings, then calculate the estimated postmortem interval.

About the Time Of Death Calculator

This calculator estimates the early postmortem interval (PMI) - the elapsed time since death - using Henssge's rectal-temperature cooling formula, the standard method taught in forensic medicine for estimates made within the first one to two days. It combines a measured rectal temperature, the ambient temperature at the scene, the body's weight, and a corrective factor for clothing and environment to solve for elapsed hours.

How the formula works

After death, the core temperature falls from an assumed starting point of 37.2°C toward the ambient temperature, following a curve that is slow at first (a thermal "plateau") and then approximately exponential. Henssge modeled this as a double-exponential equation:

  • For ambient temperatures at or below 23°C: (Trectal - Tambient) / (37.2 - Tambient) = 1.25 × e-Bt - 0.25 × e-5Bt
  • For ambient temperatures above 23°C: (Trectal - Tambient) / (37.2 - Tambient) = 1.11 × e-Bt - 0.11 × e-10Bt

Here B is a cooling-rate constant computed from body weight (M, in kg) and a corrective factor (Cf) for insulation: B = 1.2815 ÷ (Cf × M)0.625 - 0.0284. Because the equation cannot be solved for time (t) directly, the calculator searches numerically for the elapsed hours that make the right-hand side match the measured temperature ratio.

Choosing the corrective factor

The corrective factor is the largest source of controllable error. A naked body exposed to wind or wet ground loses heat quickly (Cf around 0.35-0.5); a body in typical indoor still air with no covering is close to the reference value of 1.0; clothing, bedding, or wrapping insulates the body and slows cooling (Cf of 1.2 and higher). Pick the option closest to the actual scene conditions - a mismatch here shifts the estimate more than small temperature reading errors do.

When to consult a professional

This tool performs the standard cooling-curve arithmetic for education and estimation. It is not a legal or medical determination of time of death. Actual forensic conclusions weigh this estimate alongside rigor mortis, livor mortis, stomach contents, insect activity, and scene evidence, and should be made by a medical examiner or forensic pathologist.

Frequently Asked Questions

What formula does this calculator use?
It uses Henssge's double-exponential rectal cooling formula, the standard method taught in forensic medicine for estimating the early postmortem interval. It relates the measured rectal temperature to ambient temperature, an assumed starting core temperature of 37.2°C, body weight, and a corrective factor for clothing and environment, then solves for elapsed hours since death.
How accurate is the Henssge method?
Henssge's original validation reports a 95% confidence interval of about ±2.8 hours under reference conditions (corrective factor near 1.0, moderate body weight). The interval widens for unusual clothing or environments, extreme body weight, or measurements taken long after death, so treat the result as a range, not a precise timestamp.
What is the corrective factor and why does it matter?
The corrective factor (Cf) adjusts the cooling rate for how insulated the body was: a low factor such as 0.35-0.5 applies to a naked body in wind or wet conditions, which cools quickly, while a high factor such as 1.5-2.0 applies to a heavily clothed or wrapped body, which cools slowly. Choosing the wrong factor is one of the largest sources of error in the estimate.
Can this replace a forensic pathologist's determination?
No. This tool performs the standard temperature-based arithmetic for education and estimation only. Actual time-of-death determinations combine this method with rigor mortis, livor mortis, stomach contents, entomology, and scene evidence, and should be made by a medical examiner or forensic pathologist.

Related calculators