Boiler Size Calculator

Calculate the required boiler size (BTU/h) for your home or building based on square footage, climate, and insulation.

Building Name *

What would you like to calculate? *

Square Footage *

Heated floor area

Climate Zone *

Insulation Quality *

Ceiling Height (ft) *

Average ceiling height

Number of Windows *

Windows increase heat loss

Fuel Type *

Fuel Price *

Price per gallon/therm

Boiler Efficiency (%) *

AFUE rating

Boiler Size Guide

1,500 sqft75,000 BTU

2,000 sqft100,000 BTU

2,500 sqft125,000 BTU

3,000 sqft150,000 BTU

3,500 sqft175,000 BTU

4,000 sqft200,000 BTU

🔥 Boiler Sizing Formulas:
BTU/h: (Sqft × Climate Factor × Insulation Factor × Height Factor) + Window Loss • MBH: BTU/h / 1000 • Fuel Usage: BTU/h / (Fuel Energy Content × Efficiency)

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Boiler Size Recommendation

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Step-by-Step Calculation

Detailed sizing analysis

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BTU/h

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BTU/hr

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MBH

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thousand BTU/hr

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Fuel Usage

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gal/hr

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Operating Cost

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$/hr

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Boiler Recommendation

Suggested boiler size and specifications

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Formula Reference

Boiler sizing formulas

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Boiler Tips

Choosing the right boiler

🔥 HVAC Disclaimer: Boiler size calculations are estimates. Professional load calculations (Manual J) are recommended for accurate sizing. Results are for educational purposes.