Boiler Size Calculator

Estimate boiler heating capacity from area.

Heating required (BTU/h) 70,000

Heating required (kW) 20.515

Formula: BTU = area × BTU/ft²

Step-by-step with your numbers:

1. Values used:

2. Floor area = 2,000

3. BTU per ft² = 35

5. Heating required = Floor area x BTU per ft² = 2,000 x 35 = 70,000BTU/h

6. Heating required = 20.515kW

Did we solve your problem today?

Rough-size a boiler from floor area (adjust for climate and insulation).

The math behind it

BTU/h = area × ~30–40 BTU/ft² for a typical house. ÷ 3,412 for kW.

2,000 ft² at 35 BTU/ft² → 70,000 BTU/h.

Hot water needs?

Add capacity for domestic hot water separately.