HVAC Sensible Heat Calculator
This HVAC sensible heat calculator finds the heat an air stream gains or loses from its airflow and temperature change, using the standard 1.08 × CFM × ΔT formula. Add the moisture content in and out, and it also gives the latent heat, the total heat, and the sensible heat ratio, so you can check how much of a coil's capacity goes to cooling the air and how much to drying it.
Results
The HVAC Sensible Heat Calculator is part of our Cooling & Heating collection. Browse more cooling & heating to size, convert, and check your work alongside this tool.
What the HVAC sensible heat calculator does
Sensible heat changes the temperature of air without changing its moisture; latent heat removes or adds moisture without changing temperature. An air conditioner does both. The HVAC sensible heat calculator applies the air-side formulas used in every HVAC design: sensible heat from airflow and temperature difference, latent heat from airflow and moisture difference, and their sum.
Sensible heat formula
The 1.08 comes from air density (0.075 lb/ft³) × specific heat (0.24 BTU/lb°F) × 60 minutes. The 0.68 covers density, the latent heat of water, and the grains per pound conversion. Both assume standard air near sea level.
HVAC sensible heat calculator example
1,200 CFM cooled from 75°F to 55°F, with moisture dropping from 65 to 55 grains per pound:
The total is 34,080 BTU/h, about 2.84 tons, with a sensible heat ratio of 0.76. A typical comfort cooling coil runs between 0.7 and 0.8.
How to use the sensible heat calculation tool
Enter the airflow in CFM and the air temperatures entering and leaving the coil, duct, or room in °F. For latent and total heat, also enter the moisture content of the air in grains per pound, read from a psychrometric chart or a humidity sensor. Leave the moisture fields at zero for sensible heat only. Press Calculate.
Reading sensible and latent heat
The sensible part sets how much the coil cools the air; the latent part sets how much it dries it. A low sensible heat ratio means the system spends more effort on humidity, common in humid climates and at lower airflow. In dry climates, a higher airflow and SHR near 0.85 to 0.9 suit the load. Use the total heat, not just sensible, to compare against the rated capacity of a unit.
When to use a sensible heat ratio check
- Checking the capacity a coil delivers in the field
- Converting CFM to BTU for a supply duct
- Finding the airflow a room load needs (BTU to CFM)
- Comparing summer humidity removal
- Sizing a heating coil or duct heater
Common HVAC sensible heat calculator mistakes
- Comparing sensible heat with total capacity. Add the latent part.
- Using °C with 1.08. The constant is for °F and CFM.
- Guessing airflow. Small airflow errors change the result directly.
- Ignoring altitude. Thin air carries less heat.
Tips for a total heat formula HVAC check
- Measure temperatures in the duct, not at the grille.
- Let the system run 15 minutes before reading.
- Use a psychrometric chart for moisture in grains.
Using 1.08 x CFM x delta T in the field
Measure the return and supply temperatures near the unit and the airflow with a flow hood or from the fan table. A system moving 1,200 CFM with an 18 to 20°F split is delivering roughly 23,000 to 26,000 BTU/h of sensible cooling. The split itself is easy to log with the delta T calculator. If the airflow is unknown, estimate it from the duct size and velocity with the CFM calculator.
Sensible cooling capacity vs the room load
Design starts from the load, then works back to airflow: CFM = sensible load ÷ (1.08 × ΔT). A room with a 6,000 BTU/h sensible load at a 20°F supply split needs about 278 CFM. The heat load calculator gives that starting load. At high altitude, the 1.08 factor drops with air density, by roughly 3% per 1,000 ft.
CFM to BTU: sensible heat at common temperature differences
| Airflow | ΔT 15°F (BTU/h) | ΔT 20°F (BTU/h) | ΔT 25°F (BTU/h) |
|---|---|---|---|
| 400 CFM | 6,480 | 8,640 | 10,800 |
| 800 CFM | 12,960 | 17,280 | 21,600 |
| 1,200 CFM | 19,440 | 25,920 | 32,400 |
| 1,600 CFM | 25,920 | 34,560 | 43,200 |
| 2,000 CFM | 32,400 | 43,200 | 54,000 |
HVAC Sensible Heat Calculator FAQ
What is the sensible heat formula?
Q = 1.08 × CFM × ΔT, giving BTU per hour. 1,200 CFM cooled by 20°F is 25,920 BTU/h.
What is the difference between sensible and latent heat?
Sensible heat changes air temperature; latent heat changes its moisture content.
How do I convert BTU to CFM?
CFM = BTU/h ÷ (1.08 × ΔT). A 24,000 BTU/h sensible load at a 20°F split needs about 1,111 CFM.
What is a good sensible heat ratio?
About 0.7 to 0.8 for comfort cooling in mixed climates, lower in humid climates.