Conversion method
Specific fuel energy (heating value), not vehicle distance per fuel. Mass per energy is reciprocal and requires positive values. Higher and lower heating values describe different measurements; unit conversion does not switch them.
kJ/kg = x × 0.001
10 J/kg = 0.01 kJ/kg.
| J/kg | kJ/kg |
|---|---|
| 1 | 0.001 |
| 5 | 0.005 |
| 10 | 0.01 |
| 25 | 0.025 |
| 50 | 0.05 |
| 100 | 0.1 |
Unit definitions and sources
Specific fuel energy (heating value), not vehicle distance per fuel. Mass per energy is reciprocal and requires positive values. Higher and lower heating values describe different measurements; unit conversion does not switch them.
| Unit and system | Use | Definition | Relationship |
|---|---|---|---|
| Joule per kilogram (J/kg); si | Common units | Base J/kg = value in J/kg × 1. Common use: Fuel Energy per Mass. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Kilojoule per kilogram (kJ/kg); si | Common units | Base J/kg = value in kJ/kg × 1000. Common use: Fuel Energy per Mass. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Megajoule per kilogram (MJ/kg); si | Specialist units | Base J/kg = value in MJ/kg × 1000000.0. Common use: Fuel Energy per Mass. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Thermochemical calorie per gram (cal th/g); si | Specialist units | Base J/kg = value in cal th/g × 4184. Common use: Fuel Energy per Mass. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| International Table calorie per gram (cal IT/g); si | Specialist units | Base J/kg = value in cal IT/g × 4186.8. Common use: Fuel Energy per Mass. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| BTU (IT) per pound (BTU IT/lb); si | Specialist units | Base J/kg = value in BTU IT/lb × 2326. Common use: Fuel Energy per Mass. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Kilogram per joule (kg/J); si | Specialist units | Base J/kg = 1 / value in kg/J. Common use: Fuel Energy per Mass. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Gram per kilowatt hour (g/kWh); si | Specialist units | Base J/kg = 3600000000.0 / value in g/kWh. Common use: Fuel Energy per Mass. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Btu (th)/pound (BTU th/(lb)); other | Specialist units | Btu (th)/pound = 2324.4444444444443 j-kg, derived from the component SI/customary definitions. Common use: Fuel Energy per Mass. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
Sources: NIST: SP 811 Appendix B.8: conversion factors; BIPM: SI prefixes
Precision of fuel energy per mass conversions
All 9 fuel energy per mass units convert through Joule per kilogram (J/kg). 9 have an exact defined relationship to the base unit and 0 are conventional or measured values. Results and the tables on this page come from the same engine, so a table value can be checked against the converter directly.
Standard display shows up to six decimal places, switching to scientific notation for very large or small values. Calculation uses JavaScript binary floating point independently of display rounding, so extra digits are not a claim about measurement accuracy. Each unit lists its own source; a citation records where the definition comes from, not an independent review. See Conversion methodology for the review and correction process.