Boiler Horsepower Calculator
Convert boiler horsepower (BHP) to BTU/hr, kilowatts and pounds of steam per hour instantly.
Boiler horsepower (BHP) is a steam-industry unit that rates a boiler's capacity to deliver steam — it is not the same as mechanical horsepower. This calculator converts BHP into BTU per hour, kilowatts, and pounds of steam per hour.
Boiler HP Conversion Formulas
One boiler horsepower was defined in 1876 by the American Society of Mechanical Engineers as the power needed to evaporate 34.5 pounds of water per hour "from and at 212 °F" — water already at boiling point turning entirely to steam. Multiplying 34.5 lb/hr by the latent heat of vaporization (about 970.3 BTU/lb) gives the familiar 33,475 BTU/hr figure.
How to Use This Calculator
- Enter the boiler horsepower from the boiler's nameplate or spec sheet.
- Read the heat output in BTU/hr and kW, and the steam rate in lb/hr.
Boiler HP vs. Mechanical HP — Not the Same Unit
Mechanical horsepower (746 W) measures work done by an engine or motor. Boiler horsepower (9,810 W) measures thermal energy delivered as steam — one BHP is about 13.15 times larger than one mechanical HP. They share a name for historical reasons only: early boilers were sized to feed steam engines of a given mechanical horsepower, with generous margin. Never substitute one for the other when sizing equipment.
Boiler Horsepower Conversion Table
| Boiler HP | BTU/hr | kW | Steam lb/hr |
|---|---|---|---|
| 1 | 33,475 | 9.8 | 34.5 |
| 10 | 334,750 | 98.1 | 345 |
| 50 | 1,673,750 | 490 | 1,725 |
| 100 | 3,347,500 | 981 | 3,450 |
| 200 | 6,695,000 | 1,962 | 6,900 |
| 500 | 16,737,500 | 4,905 | 17,250 |
Worked Example
Frequently Asked Questions
1 boiler horsepower equals 33,475 BTU per hour — the energy needed to evaporate 34.5 lb of water per hour from and at 212 °F.
About 9.81 kW. Multiply BHP by 9.8095 to get kilowatts of thermal output.
No. One boiler HP (9,810 W of heat) is about 13.15 times larger than one mechanical HP (746 W of work). They are different units that share a name for historical reasons.
34.5 pounds of steam per hour, evaporated from and at 212 °F. Real-world output varies with feedwater temperature and operating pressure.
Divide the BTU/hr figure by 33,475. A 1,000,000 BTU/hr boiler is about 30 BHP.