Enter the horsepower (hp) or fuel flow into the calculator. The calculator will estimate the other value using brake specific fuel consumption (BSFC), fuel density, and an engine load factor. (Horsepower does not convert to GPH as a fixed universal constant.)
- All Unit Converters
- CC to HP Calculator
- WHP to HP Calculator
- CFM to HP Calculator
- RWKW to HP Calculator
- PSI to HP Calculator
- GPH to HP Calculator
- Hydraulic Flow to HP Calculator
Hp To Gph Formula
GPH=\frac{HP\cdot BSFC \cdot LF}{\rho_{fuel}}Variables:
- GPH is the fuel flow rate in US gallons per hour.
- HP is the brake/shaft horsepower (hp).
- BSFC is brake specific fuel consumption in lb/(hp·hr).
- LF is load factor (fraction from 0 to 1; e.g., 100% load = 1.0).
- ρfuel is fuel density in lb/US gal.
There is no single universal conversion from horsepower to gallons per hour. However, you can estimate fuel flow from horsepower using BSFC, fuel density, and the operating load factor with the formula above.
| Horsepower (hp) | Fuel Flow (US GPH) |
|---|---|
| 1/16 | 0.0051 |
| ⅛ | 0.0101 |
| 1/6 | 0.0135 |
| ¼ | 0.0203 |
| ⅓ | 0.0270 |
| ⅜ | 0.0304 |
| ½ | 0.0405 |
| ⅝ | 0.0506 |
| ⅔ | 0.0540 |
| ¾ | 0.0608 |
| ⅞ | 0.0709 |
| 1 | 0.0810 |
| 1¼ | 0.1013 |
| 1⅓ | 0.1080 |
| 1½ | 0.1216 |
| 1¾ | 0.1418 |
| 2 | 0.1621 |
| 2½ | 0.2026 |
| 3 | 0.2431 |
| 4 | 0.3241 |
| *Estimates assume gasoline defaults used by this page (BSFC = 0.50 lb/(hp·hr), fuel density = 6.17 lb/US gal) at 100% load (LF = 1.0). This implies 1 hp ≈ 0.081 US GPH. | |
How to Calculate Hp To Gph?
The following steps outline how to estimate fuel flow (GPH) from horsepower (or horsepower from fuel flow) using BSFC, fuel density, and load factor.
- First, determine the horsepower (hp) or the fuel flow rate (GPH).
- Next, choose or determine the BSFC (lb/(hp·hr)), fuel density (lb/US gal), and load factor (0 to 1).
- Then use the formula: GPH = (HP × BSFC × LF) ÷ ρfuel (or rearrange to solve for HP).
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
horsepower (hp) = 456 (assume gasoline BSFC = 0.50 lb/(hp·hr), fuel density = 6.17 lb/US gal, and load factor = 100%). Estimated fuel flow: GPH = (456 × 0.50 × 1.0) ÷ 6.17 ≈ 36.95 US GPH.
FAQs
What does GPH stand for in the context of this calculator?
GPH stands for gallons per hour, a fuel flow rate. In this calculator it represents US gallons of fuel per hour (unless you select LPH or IGPH).
Why is it important to know the GPH for a given horsepower?
An estimated GPH helps with planning fuel needs and operating costs. Keep in mind horsepower alone does not determine GPH—fuel flow depends on engine efficiency (BSFC), fuel type, and load.
Can the HP to GPH formula be used for any type of engine?
The relationship here is an engineering estimate based on BSFC and fuel density, and it can be used broadly if you choose appropriate BSFC/density values for your engine and fuel. Manufacturer data or measurements are best for precise results.
Is there a way to improve the fuel efficiency reflected by the GPH value?
Yes. Improving efficiency typically means lowering BSFC for the same power output (or reducing required power): good maintenance, correct tuning, avoiding unnecessary load, and operating in an efficient RPM/load range can all reduce fuel use.
