Time of Death
Forensic time of death calculator using body temperature (algor mortis) and Glaister equation. Includes rigor mortis reference table and charts for medical use.
About This Calculator
The Time of Death Calculator estimates the time elapsed since death using two forensic methods — algor mortis (body temperature cooling) and rigor mortis (postmortem muscle stiffening). It is designed for forensic scientists, medical examiners, crime scene investigators, and pathology students who need a quick approximation of the postmortem interval (PMI).
The primary calculation uses the Glaister equation: Time since death (hours) = (98.6 — Body Temperature in °F) / T. The cooling factor T accounts for environmental conditions — below freezing (32°F / 0°C) the body cools more rapidly (T = 1.5), while above freezing the cooling is slower (T = 0.75). The result is displayed in hours and minutes for practical use in death investigations.
For a more comprehensive estimate, the calculator includes a rigor mortis reference table that correlates body temperature (warm/cold) and stiffness (flexible/stiff) to standard postmortem intervals. Rigor mortis typically begins within 2 hours, peaks at 6–8 hours, and resolves after 24–36 hours. Combining both methods — along with livor mortis (blood pooling) and other postmortem changes — improves estimation accuracy for forensic casework.
The temperature-based method works best within the first 18 hours after death, as the body gradually approaches ambient temperature and the cooling curve flattens. Clothing, body size, humidity, and air movement all influence the cooling rate and should be factored into any forensic interpretation.
Regional Notes
Worldwide: The Glaister equation uses Fahrenheit by convention, as normal body temperature of 98.6°F (37°C) is the standard reference. Input temperatures in °F or convert from Celsius using the formula (°C × 9/5 + 32 = °F). The freezing threshold is 0°C (32°F). The rigor mortis timeline is physiologically consistent across all regions and populations.
Limitations: Algor mortis estimation provides a reasonable approximation but is affected by many variables. Results should be used alongside other evidence — livor mortis, putrefaction stage, insect activity, and scene context — for forensic purposes. Always consult a qualified forensic pathologist for legal determinations.
Frequently Asked Questions
How does the time of death calculator work?
The calculator uses the Glaister equation (algor mortis) to estimate time since death. It measures the temperature drop from the normal body temperature of 98.6°F to the measured body temperature, divided by a cooling factor T that depends on the ambient temperature.
What is algor mortis?
Algor mortis is the postmortem cooling of the body until it reaches the ambient temperature. The rate of cooling depends on the environmental conditions — bodies cool faster in cold environments and slower in warm environments.
What is the formula for calculating time of death?
The Glaister equation is: Time since death (hours) = (98.6 − Body Temperature in °F) / T. When ambient temperature is below 32°F (0°C), T = 1.5. When ambient temperature is 32°F or above, T = 0.75.
How does rigor mortis help determine time of death?
Rigor mortis follows a predictable timeline: warm and flexible suggests less than 2 hours since death, warm and stiff indicates 2–8 hours, cold and stiff suggests 8–36 hours, and cold and flexible indicates more than 36 hours since death.
What factors affect algor mortis cooling rate?
Multiple factors affect cooling rate: ambient temperature (freezing vs non-freezing), clothing, body size and fat distribution, position of the body, air movement, and whether the body is in water or on land.
Can time of death be estimated in Celsius?
The Glaister equation traditionally uses Fahrenheit. To convert Celsius to Fahrenheit: multiply by 9/5 and add 32. Normal body temperature is 37°C (98.6°F), and the freezing threshold is 0°C (32°F).
How accurate is time of death estimation using body temperature?
Algor mortis estimation provides a reasonable approximation but is affected by many variables. Forensic pathologists combine it with rigor mortis, livor mortis, and other postmortem changes for a more accurate estimate. The method is most reliable within the first 12–18 hours after death.
Who uses time of death calculations?
Time of death calculations are used by forensic pathologists, medical examiners, crime scene investigators, and law enforcement to establish a timeline in suspicious death investigations. It is also studied by medical and forensic science students.