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⚡ ELECTRICAL CALCULATOR
Fuel Flow Rate Conversion Calculator
Convert fuel flow rates between gallons per hour (GPH), liters per hour (LPH), pounds per hour (lb/hr), and kilograms per hour (kg/hr). Essential for aviation, automotive, and marine engines.
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Affects mass-to-volume conversion density
Convert fuel flow rates between gallons per hour (GPH), liters per hour (LPH), pounds per hour (lb/hr), and kilograms per hour (kg/hr). Essential for aviation, automotive, and marine engines.
Converted Flow Rate
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⚠️ Disclaimer: Fuel density values are nominal at standard temperature. For aviation weight and balance, engine fuel system design, or safety-critical calculations, use certified fuel density data for your specific fuel batch and temperature conditions.
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Sources & Methodology
✓Formulas and reference data verified against authoritative sources listed below.
Fuel flow rate is a critical parameter in engine management, aviation weight and balance, fuel system design, and emissions calculations. Different industries use different units — aviation typically uses pounds per hour for weight-based calculations, automotive uses gallons or liters per hour for volume-based fuel economy, and engineering uses kg/hr for thermal calculations.
Volume vs. Mass Flow Rate
Volume flow (GPH, LPH) measures how much fuel volume passes per hour. Mass flow (lb/hr, kg/hr) measures fuel weight per hour. Mass flow is preferred in aviation because aircraft weight must be tracked precisely for load and balance calculations. The conversion between them depends on fuel density.
Fuel Density Values by Type
Fuel density varies by fuel type and temperature. At standard conditions (15°C / 59°F): Gasoline ≈ 6.0 lb/gal (0.72 kg/L); Diesel ≈ 7.1 lb/gal (0.85 kg/L); Jet-A aviation fuel ≈ 6.7 lb/gal (0.80 kg/L); Avgas 100LL ≈ 6.0 lb/gal (0.72 kg/L). Density decreases slightly at higher temperatures.
Aviation Fuel Flow Calculations
In aviation, fuel flow instruments typically display in lb/hr or GPH. Pilots use fuel flow data to calculate time to fuel exhaustion: Time = Usable Fuel ÷ Fuel Flow Rate. A Cessna 172 burning 8.5 GPH with 40 gallons usable has approximately 4.7 hours of endurance.
Automotive Fuel Economy vs. Flow Rate
Automotive fuel economy (MPG, L/100km) measures distance per volume. Fuel flow rate measures volume per time. To convert: Flow Rate (GPH) = Speed (mph) ÷ Fuel Economy (MPG). At 60 mph getting 30 MPG, flow rate is 2 GPH.
Volume conversions use 1 US gallon = 3.785 liters. Mass conversions use fuel-specific density: gasoline 6.0 lb/gal, diesel 7.1 lb/gal, Jet-A 6.7 lb/gal, Avgas 100LL 6.0 lb/gal.
Fuel Flow Conversion Formulas
Fuel Type
Density (lb/gal)
Density (kg/L)
Color
Gasoline (regular)
6.0
0.721
Clear / Slightly Yellow
Avgas 100LL
6.0
0.721
Blue
Jet-A / Jet-A1
6.7
0.803
Clear / Straw
Diesel (ULSD)
7.1
0.851
Clear / Amber
JP-8 (military)
6.7
0.803
Clear
💡 Aviation Note: Fuel density changes with temperature (approximately 0.1% per °F). For critical weight and balance calculations in aviation, use the actual fuel density at the ambient temperature, not the standard value. Many aircraft POHs provide fuel weight at various temperatures.
Frequently Asked Questions
Multiply GPH by 3.785: LPH = GPH × 3.785. For example, 10 GPH = 37.85 LPH. This is a straight unit conversion based on 1 US gallon = 3.785 liters.
Multiply GPH by the fuel's density in pounds per gallon: lb/hr = GPH × density. For gasoline (6.0 lb/gal): 10 GPH = 60 lb/hr. For diesel (7.1 lb/gal): 10 GPH = 71 lb/hr.
Jet-A aviation fuel has a density of approximately 6.7 lb/gal (0.80 kg/L) at 15°C (59°F). This value is used for weight and balance calculations in aviation, though actual density varies with temperature and fuel batch.
Aviation fuel flow is measured by fuel flow transducers and displayed on cockpit instruments in units of gallons per hour (GPH) or pounds per hour (lb/hr). Turbine engines and larger aircraft typically use lb/hr for precision weight tracking.
A typical sedan at highway speeds gets 30–40 MPG. At 65 mph, that translates to about 1.6–2.2 GPH (6–8.3 LPH). A high-performance or turbocharged vehicle might use 4–8 GPH at full throttle.
Aircraft weight and balance calculations require mass, not volume. Using lb/hr directly gives the rate of weight change, which is needed to calculate the aircraft's current weight, center of gravity, and fuel reserves over time.
These are different units measuring different things. LPH is a flow rate (volume per time), while L/100km is fuel economy (volume per distance). To convert: L/100km = (LPH ÷ Speed in km/hr) × 100.
A typical Cessna 172 burns 8–9 GPH (30–34 LPH) at cruise. A Piper Cherokee burns 9–10 GPH. Turboprops like a Pilatus PC-12 burn approximately 50–65 GPH depending on power setting.
At altitude, naturally aspirated engines receive less air density, so fuel flow decreases proportionally. A turbocharged or turbine engine maintains fuel flow better at altitude. Lean of peak operation can reduce fuel flow by 10–20% while maintaining power.
Specific fuel consumption is fuel flow per unit of power output, measured in lb/hr/hp or g/kWh. It is used to compare engine efficiency. A typical gasoline aircraft engine has a best SFC of about 0.39–0.45 lb/hr/hp.