TechTools

Radiance/Irradiance Converter

From
To
Sig. figures:

Watt per square metre

W/m²

1(input)

Milliwatt per square metre

mW/m²

1000

Microwatt per square metre

μW/m²

1.00000e+6

Kilowatt per square metre

kW/m²

0.001

Megawatt per square metre

MW/m²

1.00000e-6

Watt per square centimetre

W/cm²

0.0001

Milliwatt per square centimetre

mW/cm²

0.1

Microwatt per square centimetre

μW/cm²

100

BTU per hour per sq. foot

BTU/hr·ft²

0.316998

BTU per minute per sq. foot

BTU/min·ft²

0.0052833

BTU per second per sq. foot

BTU/s·ft²

8.80551e-5

Calorie per sec per sq. cm

cal/s·cm²

2.38846e-5

Calorie per min per sq. cm

cal/min·cm²

0.00143308

Erg per second per sq. cm

erg/s·cm²

1000

Langley per minute

Ly/min

0.00143308

Langley per hour

Ly/hr

0.0859845

Langley per day

Ly/day

2.06398

Hover any row to copy or use as input.

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Convert between all common irradiance and radiant flux density units across three groups: SI (W/m², mW/m², μW/m², kW/m², MW/m², W/cm², mW/cm², μW/cm²), Imperial (BTU/hr·ft², BTU/min·ft², BTU/s·ft²), and Thermal/Solar (cal/s·cm², cal/min·cm², erg/s·cm², Langley/min, Langley/hr, Langley/day). All groups collapsible. Adjustable significant figures, sci notation, swap, copy-per-row.

How to Use

  1. 1Enter a flux density value in the From field and choose the source unit
  2. 2Select the target unit in the To dropdown to see the instant result
  3. 3Browse SI, Imperial, and Thermal/Solar groups - collapse any group you don't need
  4. 4Hover any row and click Copy to copy that value
  5. 5Click ↕ on a row to use that value as the new input
  6. 6Open the Reference panel for solar constant, 1-sun standard, and safety thresholds

Features

  • SI group: W/m², mW/m², μW/m², kW/m², MW/m², W/cm², mW/cm², μW/cm²
  • Imperial group: BTU/hr·ft², BTU/min·ft², BTU/s·ft²
  • Thermal/Solar group: cal/s·cm², cal/min·cm², erg/s·cm², Langley/min, Langley/hr, Langley/day
  • All three groups collapsible; two-way From/To conversion with swap
  • 3–12 significant figures and scientific notation toggle
  • Reference panel with solar constant, 1-sun standard, UV safety thresholds
  • 100% browser-based - all conversions in JavaScript

Frequently Asked Questions

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