Illuminance Converter
Convert between different illuminance units including lux, foot-candles, phot, nox, and more
Conversion Settings
No value entered
Conversion Result
Conversion result will appear here
Enter a value and click "Convert" to start
Common Illuminance Values:
- • Sunlight: 100,000 lux
- • Office lighting: 300-500 lux
- • Reading: 200-300 lux
- • Street lighting: 10-20 lux
- • Moonlight: 0.1-0.3 lux
About Illuminance Converter
A comprehensive illuminance converter tool that allows you to convert between various light measurement units. Whether you're working with lighting design, photography, architecture, or scientific applications, this tool provides accurate conversions between lux, foot-candles, phot, nox, millilux, and kilolux.
Why use a Illuminance Converter?
Illuminance conversion is essential in lighting engineering, photography, architecture, and scientific research. Different regions and applications use different illuminance units - lux in most of the world, foot-candles in North America, and specialized units like phot and nox for specific applications. This tool eliminates conversion errors and saves time when working with lighting calculations.
Who is it for?
This tool is perfect for lighting engineers, photographers, architects, interior designers, students studying optics or lighting, facility managers, and anyone working with illuminance measurements that need accurate unit conversions.
How to use the tool
Enter the illuminance value you want to convert in the input field
Select the source unit from the dropdown (lux, foot-candles, etc.)
Choose the target unit you want to convert to
Click 'Convert' to see the result
Use the swap button to quickly reverse the conversion direction
Copy the result or use the clear button to start over
Frequently Asked Questions
How do I convert illuminance units?
Enter the source value, pick the 'from' and 'to' units, and click Convert to see the result. Supports lx (lux, SI), foot-candle (fc), phot, nox. 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 illuminance units does this converter support?
lx (lux, SI), foot-candle (fc), phot, nox. 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 illuminance conversion?
Conversions use the internationally-defined factors where they exist; the result is rounded to 12 significant digits for display. Both are 'photometric' units (weighted for human eye response) — different from 'radiometric' units (W/m²) which measure raw radiant energy. Use photometric for human-visible lighting; radiometric for energy balance and non-visible light. Output is rounded to 12 significant digits for display, and there is no setting to change that.
What's the formula to convert foot-candles (fc) to lux (lx)?
lx = fc × 10.7639. Workplace lighting standards (office desktops ~500 lx, reading 300-500 lx, surgical 10,000+ lx), photography (light meters often display fc or lx), agriculture (greenhouse lighting in μmol/m²/s — different unit, photosynthetic photon flux). For other illuminance-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 illuminance conversion?
**Lux (SI) vs foot-candle (US imperial)** — both measure illuminance (light falling on a surface). 1 fc = 10.7639 lx (the ratio is exactly the inverse of square feet per square metre). **Illuminance vs luminous flux** — illuminance is light per area (lx = lm/m²); flux is total light output (lumens). A 1,000 lm bulb produces different lux depending on the distance and surface area lit.
What's a common real-world use case for illuminance conversion?
Workplace lighting standards (office desktops ~500 lx, reading 300-500 lx, surgical 10,000+ lx), photography (light meters often display fc or lx), agriculture (greenhouse lighting in μmol/m²/s — different unit, photosynthetic photon flux).
What illuminance units are commonly confused?
**lx vs fc** — SI vs US imperial; 1 fc ≈ 10.76 lx. **Illuminance (lx) vs luminance (cd/m²)** — illuminance is incoming light on a surface; luminance is light emitted from a surface (display screens).
How do I handle very large or very small illuminance 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. Both are 'photometric' units (weighted for human eye response) — different from 'radiometric' units (W/m²) which measure raw radiant energy. Use photometric for human-visible lighting; radiometric for energy balance and non-visible light. For data interchange, copy the value; it is shown to 12 significant digits.
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