Room Heating Calculator

Use our room heating calculator to determine the most efficient and economical way to heat a large enclosed area.


The Room Heating Calculator is designed to be an approximate sizing guide for determining heat loss from a room. The Wizard will determine a total heat loss value based on your specific room data. The resulting value can then be used for specifying the appropriate Chromalox comfort heater for your heating needs.

1. Room Size & Specs

Length: ft. Width: ft. Height: ft.
Total Sq. Footage: ft. Room Cu. Footage: ft.
Item Area R-Factor = BTU/Hr/Degrees F
Windows Sq. ft. x =
Doors Sq. ft. x =
Net Walls Sq. ft. x =
Roof Sq. ft. x =
Floor Perimeter* Sq. ft. x =
Transmission Losses Total =

*Use the R-Factor Reference to lookup common material R-Factor values. Important: R-Factor values are additive. For example, 2" of softwood results in an R-Factor of 2 x 1.25 = 2.5.

*For floor perimeter use U-factor of 1.2 for 1" insulation or 0.7 for 2" insulation.

2. Design Information

Air Changes per hour: Outside Design Temp:
Inside Design Temp:
Temperature Difference:

3. Calculations

Air Changes Loss: Cu. Ft / hr x0.019 BTU / Cu. Ft =
Total Losses Transmission Losses + Air Change Loss =

Total Heating Requirement

Total Losses x Temperature Difference = Total BTU / Hr
BTU/Hr/Degrees F x Degrees F = BTU / Hr

Conversion to Watts

Total BTU / Hr / 3.412 BTU per watt = Total Watts per hour