Luminosity Converter
Convert between different luminosity and illuminance units including candela, lumen, lux, foot-candle, and nit. Accurate conversions for lighting calculations.
Conversion Settings
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Conversion Result
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Enter a value and click "Convert" to start
About Luminosity Converter
A comprehensive luminosity converter that handles conversions between various light measurement units including luminous intensity (candela), luminous flux (lumen), illuminance (lux, foot-candle), and luminance (nit). Essential for lighting design, photography, and engineering applications with precise conversion formulas.
Why use a Luminosity Converter?
Critical for lighting designers, photographers, engineers, and researchers who work with different light measurement standards. Prevents calculation errors in lighting projects, photography setups, and scientific measurements while supporting both professional and educational luminosity conversion needs.
Who is it for?
Essential for lighting engineers, photographers, cinematographers, architects, electrical engineers, and students studying optics or lighting design. Also valuable for interior designers, stage lighting technicians, and anyone working with illumination specifications across different measurement systems.
How to use the tool
Enter your luminosity value in the input field
Select the source unit (candela, lumen, lux, foot-candle, or nit); the target list only shows units of the same quantity
Choose your target unit for conversion
View the converted value
Copy the result for use in lighting calculations or specifications
Frequently Asked Questions
How do I convert luminosity units?
Enter the source value, pick the 'from' and 'to' units, and click Convert to see the result. Supports intensity (cd, mcd, kcd, candle), flux (lm, mlm, klm), illuminance (lx, fc, mlx, klx, phot) and luminance (nit, cd/m², foot-lambert, lambert, stilb, apostilb). Units convert within the same quantity only; the tool does not convert between cd and lm, or use lm/W or W. Copy the converted value to clipboard. Conversion runs entirely in your browser — values never leave the device. Results are shown to up to 12 significant digits with trailing zeros removed; there is no precision setting.
What luminosity units does this converter support?
Intensity (cd, mcd, kcd, candle), flux (lm, mlm, klm), illuminance (lx, fc, mlx, klx, phot) and luminance (nit, cd/m², foot-lambert, lambert, stilb, apostilb). The set covers SI base and derived units, common imperial/US-customary units, and domain-specific units where relevant. SI prefixes (k, M, G, m, μ, n) apply where applicable. For any unit not in the list that you need converted, mention it via feedback — the unit set evolves based on user requests.
How accurate is the luminosity conversion?
SI and photometric factors are exact, while the historical international candle (1.019 cd) is approximate; the result is rounded to 12 significant digits for display. Candela is a SI base unit (one of seven), defined since 1979 via the luminous efficacy of monochromatic radiation at 540 THz (green light). Lumen = candela × solid angle (sr). Output is rounded to 12 significant digits for display, and there is no setting to change that.
What's the formula to convert candela (cd) to lumens (lm) at uniform sphere?
This tool does not convert between candela and lumens, because that needs the beam pattern. By hand, for an omnidirectional source lm = cd × 4π. Light bulb specifications (lumens for total brightness, lm/W for efficiency), flashlight ratings (cd for beam intensity), LED design (lm/W is the efficacy benchmark — modern LEDs reach 200+ lm/W). For other luminosity-unit pairs, the tool applies the appropriate exact conversion factor automatically — no manual formula needed. Results are rounded to 12 significant digits, which is more than engineering specs typically need.
What's the key accuracy caveat for luminosity conversion?
**Candela (cd) vs lumen (lm) — different concepts**. Candela measures luminous intensity in a specific direction (light per solid angle). Lumen measures total luminous flux (light output in all directions). For a uniform omnidirectional source, 1 cd = 4π lm ≈ 12.57 lm. For directional sources (LEDs, flashlights), the lm and cd values depend on the beam pattern. **Lumens per watt (lm/W)** measures efficacy — how much visible light per electrical power consumed.
What's a common real-world use case for luminosity conversion?
Light bulb specifications (lumens for total brightness, lm/W for efficiency), flashlight ratings (cd for beam intensity), LED design (lm/W is the efficacy benchmark — modern LEDs reach 200+ lm/W).
What luminosity units are commonly confused?
**Candela (cd) vs lumen (lm)** — directional intensity vs total flux. **Lumen vs lux** — lumen is light output; lux is illuminance (lumens per square metre on a surface).
How do I handle very large or very small luminosity values?
Use SI prefixes for clean scaling: kilo (10³), mega (10⁶), giga (10⁹), milli (10⁻³), micro (10⁻⁶), nano (10⁻⁹). For very large or very small results, the tool switches to exponent notation (e.g. 1.23e15) at 1e15 and above or below 1e-9. Candela is a SI base unit (one of seven), defined since 1979 via the luminous efficacy of monochromatic radiation at 540 THz (green light). Lumen = candela × solid angle (sr). For data interchange, copy the value; it is shown to 12 significant digits.
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