Thermal Comfort PMV Calculator
The Predicted Mean Vote (PMV) index, developed by Professor P.O. Fanger and standardized in ASHRAE Standard 55 and ISO 7730, is the most widely used measure of building thermal comfort. PMV predicts the average thermal sensation of a group of people on a seven-point scale from -3 (cold) to +3 (hot), with 0 being thermally neutral. It depends on six variables: air temperature, mean radiant temperature, air velocity, humidity, metabolic rate (activity level), and clothing insulation. This calculator uses a simplified formulation where mean radiant temperature equals air temperature and a low air velocity is assumed, suitable for typical office environments.
Simplified PMV formula (Fanger)
L = M - W - C - R - Ersw - Edif - Cres - Eres
PMV = (0.303 * e^(-0.036*M) + 0.028) * L
Simplified: PMV approx 0.303 * e^(-0.036*M*58.2) * (55*M - 0.24*(Ta + 273.15) - 2*RH + 58*Icl - 0.42*(55*M - 58.15))
PPD (%) = 100 - 95 * e^(-(0.03353 * PMV^4 + 0.2179 * PMV^2))
This is a simplified Fanger PMV equation suitable for standard office conditions. The full equation requires solving for clothing surface temperature iteratively. This implementation assumes mean radiant temperature equals air temperature and air velocity is 0.1 m/s (still air). For precision HVAC design, use the full ISO 7730 algorithm with measured radiant temperature and air velocity.
ASHRAE 55 comfort context
- ASHRAE Standard 55-2020 defines acceptable thermal conditions as PMV between -0.5 and +0.5 for 80 percent occupant satisfaction.
- The associated PPD (Predicted Percentage Dissatisfied) is always at least 5 percent even at PMV = 0, reflecting individual variation in thermal preference.
- Building energy use for heating and cooling accounts for about 40 percent of US energy consumption (EIA). Widening acceptable comfort ranges by 1 degree can reduce HVAC energy use by 5 to 10 percent.
- ASHRAE's adaptive comfort model (for naturally ventilated buildings) allows wider temperature ranges based on outdoor running mean temperature, reflecting occupant adaptation.
- The WELL Building Standard and LEED v4 reference ASHRAE 55 for their indoor environmental quality credits.
Frequently asked questions
What is the Predicted Mean Vote (PMV)?
PMV is a thermal comfort index developed by P.O. Fanger that predicts the mean thermal sensation vote of a large group of people on a scale from -3 (cold) to +3 (hot), with 0 representing neutral comfort. It is the basis of ASHRAE Standard 55 and ISO 7730 for building thermal comfort.
What does the PMV scale mean?
The ASHRAE 7-point thermal sensation scale: -3 Cold, -2 Cool, -1 Slightly cool, 0 Neutral, +1 Slightly warm, +2 Warm, +3 Hot. ASHRAE Standard 55 recommends PMV be within -0.5 to +0.5 for 80 percent occupant acceptance.
What is the clo unit for clothing?
The clo (clothing insulation unit) measures the thermal insulation of clothing. 0 clo = naked; 0.5 clo = light summer clothing (shorts and T-shirt); 1.0 clo = typical business suit; 1.5 clo = heavy sweater and pants; 2.0 clo = heavy winter clothing and coat.
What is the met unit for metabolic activity?
The met (metabolic equivalent of task) measures metabolic rate relative to seated rest. 1 met = 58.2 W/m2 (seated at rest); 1.2 met = sedentary office work; 2.0 met = standing light work or slow walking; 3.0 met = brisk walking; 4.0 met = light exercise.
Why is ASHRAE Standard 55 important?
ASHRAE Standard 55 (Thermal Environmental Conditions for Human Occupancy) is the primary US standard for indoor thermal comfort. It is referenced in building codes and green building rating systems (LEED, WELL). The standard defines acceptable thermal conditions for HVAC design to achieve satisfactory comfort for 80 percent of occupants.
Official sources
- ASHRAE: ASHRAE Standard 55 Thermal Comfort.
- ASHRAE: ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers).
- EPA: EPA Indoor Air Quality and Building Energy.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.