Boiler Sizing Calculator

Size hot water and steam boilers for commercial and residential heating.

Heat Load

Boiler Type

System Factors

Standard Boiler Sizes

BHPMBH OutputInput (Gas)
501,6752,100 MBH
1003,3504,200 MBH
1505,0256,300 MBH
2006,7008,400 MBH
30010,05012,600 MBH

1 BHP = 33,475 BTU/hr output

Design Guidelines

Piping Loss: 5-15% for insulated, 15-25% uninsulated

Pickup Factor: 10-20% for intermittent heating

Multiple Boilers: Consider N+1 redundancy

Turndown: Modulating boilers 5:1 to 10:1