Supply Air Temperature Rise Calculator
Furnace temperature rise from CFM and BTU.
Enter your values
ⓘ Live results
Results
- Temperature rise
- 52.9 °F
- Assessment
- Within typical rated range
Quick answer
Temperature rise across a furnace equals its heat output divided by 1.08 times the system airflow in CFM.
ΔT = BTU/hr output / (1.08 x CFM)
How to use the Supply Air Temperature Rise Calculator
- 1Enter the furnace's rated heating output in BTU per hour.
- 2Enter the system's actual airflow in CFM at the current blower speed.
- 3Compare the resulting temperature rise to the furnace nameplate's rated rise range.
Worked example
Using the values the calculator loads with:
Inputs
- Furnace output80000 BTU/hr
- System airflow1400 CFM
Results
- Temperature rise52.9 °F
- AssessmentWithin typical rated range
Frequently asked questions
Why does temperature rise matter?
Running outside the furnace's rated rise range risks overheating the heat exchanger or delivering lukewarm air.
How do I fix a high rise?
Check for a dirty filter, closed dampers or undersized ducts restricting airflow, or increase blower speed.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.