Conversion method
Energy deposited per area, sometimes called heat density. This is not volumetric energy density or heat-flow rate per area. Langley means one thermochemical calorie per square centimeter.
kJ/m² = x × 0.001
10 J/m² = 0.01 kJ/m².
| J/m² | kJ/m² |
|---|---|
| 1 | 0.001 |
| 5 | 0.005 |
| 10 | 0.01 |
| 25 | 0.025 |
| 50 | 0.05 |
| 100 | 0.1 |
Unit definitions and sources
Energy deposited per area, sometimes called heat density. This is not volumetric energy density or heat-flow rate per area. Langley means one thermochemical calorie per square centimeter.
| Unit and system | Use | Definition | Relationship |
|---|---|---|---|
| Joule per square meter (J/m²); si | Common units | Base J/m² = value in J/m² × 1. Common use: Heat Energy per Area. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Kilojoule per square meter (kJ/m²); si | Common units | Base J/m² = value in kJ/m² × 1000. Common use: Heat Energy per Area. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Thermochemical calorie per square centimeter (cal th/cm²); si | Specialist units | Base J/m² = value in cal th/cm² × 41840. Common use: Heat Energy per Area. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Langley (Ly); si | Specialist units | Base J/m² = value in Ly × 41840. Common use: Heat Energy per Area. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| BTU (IT) per square foot (BTU IT/ft²); si | Specialist units | Base J/m² = value in BTU IT/ft² × 11356.526682226975. Common use: Heat Energy per Area. Source checked 2026-09-20 (implementation review). | Exact definition; numerical display may be rounded |
| Btu (th)/square foot (BTU th/(ft²)); other | Specialist units | Btu (th)/square foot = 11348.931794792601 j-m2, derived from the component SI/customary definitions. Common use: Heat Energy per Area. 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 heat energy per area conversions
All 6 heat energy per area units convert through Joule per square meter (J/m²). 6 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.