Calculator Inputs
Example Data Table
| Case | Air °F | Radiant °F | Air fpm | RH % | Met | Clo | Expected Feel |
|---|---|---|---|---|---|---|---|
| Office desk | 75 | 75 | 20 | 50 | 1.2 | 0.5 | Near neutral |
| Cool meeting room | 68 | 68 | 25 | 45 | 1.1 | 0.7 | Slightly cool |
| Warm lobby | 80 | 81 | 15 | 55 | 1.3 | 0.5 | Slightly warm |
Formula Used
This tool uses the predicted mean vote method. Imperial inputs are first converted to metric units. Air temperature and mean radiant temperature move from Fahrenheit to Celsius. Air speed moves from feet per minute to meters per second. Clothing insulation is converted from clo to square meter kelvin per watt. Metabolic rate is converted from met to watts per square meter.
The PMV equation balances body heat production against heat losses from evaporation, sweating, respiration, radiation, and convection. The calculator then estimates PPD, or predicted percentage dissatisfied, from the PMV value. A PMV near zero suggests neutral thermal sensation. A lower value suggests cool discomfort. A higher value suggests warm discomfort.
Main relation: PPD = 100 - 95 × e[-0.03353 × PMV⁴ - 0.2179 × PMV²].
How to Use This Calculator
- Enter air temperature in degrees Fahrenheit.
- Enter mean radiant temperature in degrees Fahrenheit.
- Add air speed in feet per minute.
- Enter indoor relative humidity as a percentage.
- Set activity level in met units.
- Set clothing insulation in clo units.
- Press the calculate button.
- Review PMV, PPD, and comfort status above the form.
Imperial PMV Comfort Guide
What This Calculator Measures
Thermal comfort is not based on temperature alone. People react to air movement, humidity, clothing, activity, and radiant surfaces. This calculator brings those factors together. It gives one practical comfort score called PMV. It also gives PPD. That value estimates the share of people who may feel dissatisfied in the same space.
Why Imperial Inputs Help
Many building teams in the United States record field data in imperial units. Thermometers show degrees Fahrenheit. Airflow meters may show feet per minute. This page accepts those familiar units. It then converts values internally for the comfort model. That keeps data entry simple. It also keeps the calculation aligned with accepted engineering practice.
Reading the PMV Value
A PMV of zero means neutral sensation. Positive values mean the space feels warm. Negative values mean the space feels cool. Many projects target a band near zero. A common comfort band is between minus 0.5 and plus 0.5. This range does not please everyone. It does show that most occupants should feel reasonably comfortable.
Using PPD for Decisions
PPD makes the result easier to explain. A lower PPD means fewer expected complaints. A higher PPD means more possible dissatisfaction. Facility teams can compare several operating conditions with this value. They can test higher air speed, lighter clothing, or small setpoint changes.
Important Field Notes
Good input quality matters. Measure air temperature near occupied height. Check radiant temperature near windows, exterior walls, or hot equipment. Use realistic clothing and activity values. Do not treat PMV as a perfect prediction. Drafts, sunlight, floor temperature, personal preference, age, and adaptation can change comfort. Still, PMV is useful for screening indoor conditions. It supports better discussions between designers, operators, and occupants. Use repeated readings for stronger comfort planning.
FAQs
What is PMV?
PMV means predicted mean vote. It estimates average thermal sensation on a cold to hot scale using temperature, humidity, air speed, clothing, and activity.
What is PPD?
PPD means predicted percentage dissatisfied. It estimates how many occupants may feel thermally uncomfortable under the same room conditions.
Why does this calculator use imperial entries?
Many users collect building readings in Fahrenheit and feet per minute. The calculator accepts those values and converts them internally.
What PMV range is comfortable?
A common target is between -0.5 and +0.5. This range suggests near neutral comfort for many indoor spaces.
What does clo mean?
Clo measures clothing insulation. Light summer clothing may be near 0.5 clo. Heavier indoor clothing may be near 1.0 clo.
What does met mean?
Met describes activity level. Seated office work is often near 1.2 met. Walking or active work needs higher values.
Can PMV predict every person’s comfort?
No. PMV gives a group estimate. Personal preference, health, drafts, sunlight, and adaptation can change individual comfort.
Can I download the results?
Yes. After calculating, use the CSV button for spreadsheet data or the PDF button for a printable report.