Heat Flux Density Converter

How to Use

1. 1Type a heat flux density value in the input field
2. 2Select your starting unit from the From dropdown - choose from SI / Metric, BTU / US Customary, or Caloric
3. 3Select your target unit from the To dropdown - the result appears instantly
4. 4All 16 conversions appear simultaneously, grouped by unit system
5. 5Hover any result row to reveal the copy (📋) and use-as-input (⇅) buttons
6. 6Click the copy icon to copy a value to your clipboard
7. 7Click ⇅ on any row to use that unit and value as the new input for instant reverse conversion
8. 8Use the ⇄ button between From and To to swap both units while updating the value
9. 9Adjust 'Sig. figures' to control result precision (3 to 12 significant digits)
10. 10Toggle 'Sci notation' for very small values such as mW/m² or very large values such as kW/cm²
11. 11Collapse a group by clicking its header to reduce clutter when you only need one unit system
12. 12Open 'Common conversions & heat transfer reference' at the bottom for a quick-reference table including the solar constant and standard fire-test value

Features

• 16 heat flux density units across 3 unit systems
• SI / Metric: W/m², kW/m², MW/m², mW/m², W/cm², kW/cm², W/mm²
• BTU / US Customary: BTU/(hr·ft²), BTU/(s·ft²), BTU/(min·ft²), BTU/(hr·in²), BTU/(s·in²)
• Caloric: cal/(s·cm²), cal/(min·cm²), kcal/(hr·m²), kcal/(hr·cm²)
• Includes W/m² - the SI standard for solar irradiance and thermal analysis
• Includes BTU/(hr·ft²) - the dominant unit in HVAC and North American building codes
• All 16 conversions shown simultaneously - no need to select a single target unit
• Click any result row to use it as the new input for instant reverse conversion
• Adjustable significant figures: 3, 4, 5, 6, 8, 10, or 12 digits
• Toggleable scientific notation for very small or very large values
• Collapsible unit-system groups to reduce visual clutter
• One-click copy to clipboard for any converted value
• Quick-reference table with 12 key conversions including solar constant and fire-test reference
• Exact factors: 1 BTU = 1055.05585262 J, 1 ft² = 0.09290304 m², 1 cal = 4.184 J (all NIST-traceable)
• Default: 1 W/m² → BTU/(hr·ft²) (most common heat flux conversion)
• 100% browser-based - no server, no data upload

Frequently Asked Questions