How to Calculate Boiler Sizing
What is Boiler Sizing?
Boiler Sizing Calculator helps contractors and tradespeople accurately size, spec, and estimate materials and systems.
Formula
Boiler BTU = Heat Loss (BTU/hr) × Safety Factor (1.25)
Step-by-Step Guide
- 1Calculate building heat loss through walls, windows, roof
- 2Apply the formula using your project measurements
- 3Add required safety factors or waste allowances per code
Worked Examples
Input
80,000 BTU/hr heat loss
Result
Boiler = 80,000 × 1.25 = 100,000 BTU input
Common Mistakes to Avoid
- ✕Not applying code-required safety factors or derating
- ✕Forgetting to account for waste and cut losses in material estimates
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