Heating Calculator
Radiator Sizing Calculator
Use our free radiator sizing calculator to accurately determine the heating requirements (in BTUs) for any room. Perfect for selecting the right size hydronic radiator based on room dimensions and insulation quality.
Table of Contents
Room Parameters
Heating Requirement
Recommended radiator heat output
Radiator Sizing Formula
Volume (cu ft) = Length × Width × Height
Base BTU = Volume × Base Factor
Required BTU = Base BTU × Room Multiplier × Wall Multiplier
Base Factor = Based on insulation (Good=4, Average=5, Poor=6).
Room Multiplier = Living (1.1), Bedroom (1.0), Bathroom (1.2), Kitchen (1.0), Hallway (1.1).
Wall Multiplier = Depending on number of outside walls (1 wall = 1.1, 2 walls = 1.2, 3 walls = 1.3).
Common Room Heat Requirements (BTU/hr)
| Room Size | Insulation Quality | Approx. BTU Needed |
|---|---|---|
| Small (100 sq ft) | Good | ~3,600 |
| Small (100 sq ft) | Poor | ~5,400 |
| Medium (200 sq ft) | Average | ~9,000 |
| Large (300 sq ft) | Average | ~13,500 |