Radiance/Irradiance Converter

Convert between W/m², mW/cm², BTU/hr·ft², cal/cm²·min, erg/cm²·s, and solar flux units. Essential for optics, solar energy, environmental science, and engineering.

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Common Conversions
Quick access to frequently used conversions
Unit Information

Metric Units

International System of Units (SI) measurements

W/m²
metric
Watts per Square Meter
Watts per square meter (SI unit)
mW/m²
metric
Milliwatts per Square Meter
Milliwatts per square meter
μW/m²
metric
Microwatts per Square Meter
Microwatts per square meter
W/cm²
metric
Watts per Square Centimeter
Watts per square centimeter
mW/cm²
metric
Milliwatts per Square Centimeter
Milliwatts per square centimeter
kW/m²
metric
Kilowatts per Square Meter
Kilowatts per square meter

Imperial Units

Traditional British and American measurements

W/ft²
imperial
Watts per Square Foot
Watts per square foot
BTU/hr·ft²
imperial
BTU per Hour per Square Foot
British Thermal Units per hour per square foot

Scientific Units

Scientific and technical measurements

cal/cm²·min
scientific
Calories per Square Centimeter per Minute
Calories per square centimeter per minute
erg/cm²·s
scientific
Ergs per Square Centimeter per Second
Ergs per square centimeter per second
SFU
scientific
Solar Flux Units
Solar flux units (10⁻²² W/m²/Hz)
Preferences

Applications

Solar Energy

  • • Solar panel efficiency calculations
  • • Solar irradiance measurements
  • • Solar thermal system design
  • • Solar resource assessment

Optics & Photonics

  • • Laser power density measurements
  • • Optical system design
  • • Light intensity calculations
  • • Photodetector calibration

Environmental Science

  • • Climate research and modeling
  • • Atmospheric radiation studies
  • • UV index calculations
  • • Solar radiation monitoring

Engineering

  • • Heat transfer calculations
  • • Thermal system design
  • • Building energy analysis
  • • Industrial process control

Radiance and Irradiance Units

SI Units

W/m²: Watts per square meter (standard SI unit)

mW/m²: Milliwatts per square meter

μW/m²: Microwatts per square meter

nW/m²: Nanowatts per square meter

pW/m²: Picowatts per square meter

kW/m²: Kilowatts per square meter

Area-Based Units

W/cm²: Watts per square centimeter

mW/cm²: Milliwatts per square centimeter

W/ft²: Watts per square foot

BTU/hr·ft²: British Thermal Units per hour per square foot

cal/cm²·min: Calories per square centimeter per minute

Specialized Units

erg/cm²·s: Ergs per square centimeter per second

solar flux units: Solar flux units (10⁻²² W/m²/Hz)

Langley: 1 cal/cm² (historical unit)

Solar constant: ~1361 W/m² at Earth's orbit

Standard conditions: 25°C, 1 atm pressure

About Radiance and Irradiance Conversion

Radiance and irradiance conversion involves converting between different units of power per unit area. These measurements are crucial for understanding light intensity, solar radiation, and thermal energy transfer in various scientific and engineering applications.

Key Relationships

  • • 1 W/m² = 1000 mW/m² = 1,000,000 μW/m²
  • • 1 W/cm² = 10,000 W/m² = 10 kW/m²
  • • 1 W/ft² = 10.76 W/m²
  • • 1 BTU/hr·ft² = 3.15 W/m²
  • • 1 cal/cm²·min = 697.8 W/m²
  • • 1 erg/cm²·s = 0.001 W/m²

Common Irradiance Values

  • Moonlight: 0.001 W/m²
  • Indoor Lighting: 10-100 W/m²
  • Sunlight (Cloudy): 100-500 W/m²
  • Sunlight (Clear): 800-1200 W/m²
  • Laser Pointer: 1000-10000 W/m²
  • Industrial Laser: 10⁶-10¹² W/m²
  • Solar Constant: 1361 W/m²

This converter provides precise conversions between all radiance and irradiance units, making it easy to work with any measurement scale. Whether you're designing solar energy systems, conducting optical research, or analyzing environmental data, our radiance converter ensures accurate and reliable results.

Scientific Background

Irradiance is a measure of the power of electromagnetic radiation per unit area incident on a surface. It is fundamental to understanding energy transfer through radiation and is used extensively in physics, engineering, and environmental science.

Physical Principles

  • Power Density: Energy per unit time per unit area
  • Wavelength Dependence: Varies with electromagnetic spectrum
  • Distance Effect: Follows inverse square law
  • Atmospheric Effects: Absorption and scattering
  • Surface Properties: Reflectance and absorption

Measurement Methods

  • Pyranometers: Measure total solar irradiance
  • Pyrheliometers: Measure direct solar radiation
  • Photodiodes: Convert light to electrical current
  • Thermopiles: Measure thermal effects of radiation
  • Spectroradiometers: Measure spectral distribution

Understanding radiance and irradiance is crucial in solar energy, optics, climate science, and many other fields. Our converter provides the mathematical relationships needed to work with these measurements across different unit systems and applications.

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