Convert Joules per Kilogram to Pounds per Horsepower-hour
Joule per Kilogram (J/kg) to Pound per Horsepower-hour (lb/(hp·h)) mass-basis fuel efficiency conversion — enter any value below to get an instant result, or use the table for common values.
Results from this calculator are estimates provided for general informational purposes only, based on formulas, rates, and standards commonly accepted as of 2026. Figures may differ slightly from other calculators or professional sources due to rounding methods, differing assumptions, or regional regulations, and rules may change over time. Always consult a qualified professional — such as a financial advisor, healthcare provider, or other relevant specialist — before making decisions based on these results.
Result
1 J/kg = 5918352.5 lb/(hp·h)
1 Joule per Kilogram = 5918352.5 Pounds per Horsepower-hour
1 Pound per Horsepower-hour = 5918352.5 Joules per Kilogram
1 J/kg in every supported unit
Conversion chart: Joule per Kilogram to Pounds per Horsepower-hour
Conversion table
| Joule per Kilogram (J/kg) | Pound per Horsepower-hour (lb/(hp·h)) |
|---|---|
| 0.01 J/kg | 5.9183525E+08 lb/(hp·h) |
| 0.1 J/kg | 59183525 lb/(hp·h) |
| 1 J/kg | 5918352.5 lb/(hp·h) |
| 2 J/kg | 2959176.3 lb/(hp·h) |
| 3 J/kg | 1972784.2 lb/(hp·h) |
| 5 J/kg | 1183670.5 lb/(hp·h) |
| 10 J/kg | 591835.25 lb/(hp·h) |
| 20 J/kg | 295917.63 lb/(hp·h) |
| 50 J/kg | 118367.05 lb/(hp·h) |
| 100 J/kg | 59183.525 lb/(hp·h) |
| 1000 J/kg | 5918.3525 lb/(hp·h) |
Joule per Kilogram (J/kg)
Definition: The SI derived unit of specific energy — how many joules of energy are released by burning (or otherwise extracting energy from) one kilogram of a fuel or material.
History: A direct combination of the SI joule and kilogram, adopted as the coherent scientific unit for specific energy once both base units were standardized internationally.
Current use: Used in physics and engineering calculations of calorific value, battery energy density, and food energy content wherever SI-consistent units are required throughout a larger calculation.
Pound per Horsepower-hour (lb/(hp·h))
Definition: A classic specific fuel consumption (SFC) rating for reciprocating and turbine engines — pounds of fuel burned per horsepower of output sustained for one hour.
History: Standardized in the early-to-mid 20th century aviation and marine engine industries, when engine output was rated in horsepower and fuel was measured by weight for aircraft loading calculations.
Current use: Still used in piston aero-engine and some marine engine specifications, particularly in the US and in historical/vintage engine documentation.
Supported Units
| Unit | Symbol | Category |
|---|---|---|
| Joule per Kilogram | J/kg | Specific energy (energy/mass) |
| Kilojoule per Kilogram | kJ/kg | Specific energy (energy/mass) |
| Calorie (IT) per Gram | cal/g | Specific energy (energy/mass) |
| Btu (IT) per Pound | Btu/lb | Specific energy (energy/mass) |
| Kilogram per Kilojoule | kg/kJ | Specific fuel consumption (mass/energy) |
| Gram per Calorie (IT) | g/cal | Specific fuel consumption (mass/energy) |
| Pound per Btu (IT) | lb/Btu | Specific fuel consumption (mass/energy) |
| Pound per Horsepower-hour | lb/(hp·h) | Specific fuel consumption (mass/energy) |
| Gram per Kilowatt-hour | g/kWh | Specific fuel consumption (mass/energy) |
About These Parameters
- Value
- The fuel-efficiency figure you want to convert, expressed in the "From" unit. Accepts decimals.
- From Unit
- The unit your input value is currently measured in — a specific-energy unit like J/kg or Btu/lb, or an engine SFC unit like g/kWh.
- To Unit
- The unit you want the result converted into. Use the swap button to flip From and To instantly.
How Fuel Efficiency - Mass Conversion Works
The Formula
Within the same group (both specific energy, or both specific fuel consumption), conversion is a simple multiplication:
result = value × (factor of "From" unit ÷ factor of "To" unit)
Crossing between the two groups instead inverts through the base unit:
SFC unit = (factor of SFC unit) ÷ (value × factor of specific-energy unit)
For Joule per Kilogram → Pound per Horsepower-hour: 1 J/kg = 5918352.5 lb/(hp·h).
Specific Energy vs. Specific Fuel Consumption
Specific energy (J/kg, cal/g, Btu/lb) describes a fuel's raw calorific value — an intrinsic property of the fuel itself, independent of any engine. Specific fuel consumption (g/kWh, lb/(hp·h)) instead describes how efficiently a real engine turns that stored energy into usable mechanical output, and depends on the engine's thermal efficiency, not just the fuel. A lower SFC figure always means a more fuel-efficient engine, the opposite direction from specific energy, where a higher figure means a more energy-dense fuel.
Why g/kWh Replaced lb/(hp·h)
Pounds per horsepower-hour was the standard engine efficiency rating through the early-to-mid 20th century, when horsepower was the universal power unit in aviation and marine engineering. As engine testing and international trade shifted to the metric kilowatt, grams per kilowatt-hour became the global standard — it's the figure printed on virtually every modern diesel and gasoline engine's technical datasheet today.
Example
A diesel engine rated at 200 g/kWh converts to about 0.32879736 lb/(hp·h) — a typical figure for a modern, efficient diesel; older or smaller gasoline engines often run well above 250 g/kWh.
Frequently Asked Questions
How many Pounds per Horsepower-hour are in 1 Joule per Kilogram?
1 Joule per Kilogram (J/kg) equals exactly 5918352.5 Pounds per Horsepower-hour (lb/(hp·h)).
Why does a lower g/kWh mean a better engine, when higher J/kg means a better fuel?
They measure different things in opposite directions. J/kg (specific energy) is a property of the fuel — more energy per kilogram is always better. g/kWh (specific fuel consumption) is a property of the engine — it asks how much fuel mass is spent to deliver one unit of output, so less fuel for the same output means a more efficient engine.
Can I convert a fuel's calorific value directly into an engine's SFC rating?
This converter performs the mathematical reciprocal between the two groups, but that number alone assumes a perfectly (100%) efficient engine. Real engines lose energy to heat, friction, and exhaust, so an actual SFC rating is always numerically worse (higher) than the theoretical reciprocal of the fuel's calorific value.
How accurate are these conversions?
Every conversion factor used here is the exact, internationally recognized relationship between the underlying energy, mass, and power units (e.g. 1 kWh = exactly 3,600,000 joules) — results are limited only by floating-point display precision, not by rounded conversion constants.