Calculate fuel flow in GPH from engine horsepower using BSFC, fuel density and load factor, plus fuel cost per hour and run time on your tank.
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Hp To Gph Formula
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/(hpยทhr).
- LF is load factor (fraction from 0 to 1; e.g., 100% load = 1.0).
- ฯfuel 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 |
| โ | 0.0101 |
| 1/6 | 0.0135 |
| ยผ | 0.0203 |
| โ | 0.0270 |
| โ | 0.0304 |
| ยฝ | 0.0405 |
| โ | 0.0506 |
| โ | 0.0540 |
| ยพ | 0.0608 |
| โ | 0.0709 |
| 1 | 0.0810 |
| 1ยผ | 0.1013 |
| 1โ | 0.1080 |
| 1ยฝ | 0.1216 |
| 1ยพ | 0.1418 |
| 2 | 0.1621 |
| 2ยฝ | 0.2026 |
| 3 | 0.2431 |
| 4 | 0.3241 |
| *Estimates assume gasoline defaults used by this page (BSFC = 0.50 lb/(hpยทhr), fuel density = 6.17 lb/US gal) at 100% load (LF = 1.0). This implies 1 hp โ 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/(hpยทhr)), fuel density (lb/US gal), and load factor (0 to 1).
- Then use the formula: GPH = (HP ร BSFC ร LF) รท ฯfuel (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/(hpยทhr), fuel density = 6.17 lb/US gal, and load factor = 100%). Estimated fuel flow: GPH = (456 ร 0.50 ร 1.0) รท 6.17 โ 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 GPHโfuel 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.
