Heat Density Converter

Heat density is heat energy per area, the energy that reaches or passes through a surface: q = Q / A. Its SI unit is the joule per square meter (J/m²). It is not a rate; heat per area and time, such as W/m², is in the Heat Flux Density Converter.

Two uses keep the older units alive:

• Solar radiation, measured in langleys, one calorie per square centimeter. A clear summer day can deliver 500 to 700 Ly to the ground.
• Arc flash, where the incident energy of an electrical fault and the rating of protective clothing are given in cal/cm². About 1.2 cal/cm² on bare skin is enough for a second-degree burn.

How to convert heat density

Type a value into any field, and every other unit is calculated at once. For example, protective clothing rated at 8 cal/cm²:

1. In J/m²: multiply by 41,840.

   8 * 41,840 = 334,720 J/m²

2. In J/cm²: a square meter is 10,000 cm², so divide that by 10,000.

   334,720 / 10,000 = 33.47 J/cm²

And a day of 600 Ly of sunshine is 600 * 41,840 = 25,104,000 J/m², about 25.1 MJ/m².

Common conversions

Heat density units

• Joule / meter² (J/m²): The Joule per Square Meter represents the amount of energy, measured in joules, distributed across an area of one square meter.
  Conversion Factor: 1 J/m² = 1 J/m² (Base Unit)

• Calorie (th) / centimeter² (cal/cm²): The Calorie per Square Centimeter signifies the heat energy, measured in calories, spread over one square centimeter.
  Conversion Factor: 1 cal/cm² = 41,840 J/m²

• Langley (Ly): The Langley is a unit of heat density that corresponds to one calorie per square centimeter.
  Conversion Factor: 1 Ly = 1 cal/cm² = 41,840 J/m²

• Btu / foot² (Btu/ft²): The British Thermal Unit per Foot² denotes the heat energy, measured in BTUs, distributed over one square foot.
  Conversion Factor: 1 Btu (IT) / ft² = 11,356.5 J/m²; 1 Btu (th) / ft² = 11,348.9 J/m²