Illuminance Converter

An illuminance converter translates how much luminous flux falls on a surface per unit area. This free tool handles lux (lx), foot-candles (fc), and phot (ph) — the standard units for lighting design, workplace standards, photography exposure guides, and architectural specs.

Illuminance is measured in lumens per square metre (1 lx = 1 lm/m²). Enter a value, pick From and To units, and read the result instantly. All illuminance unit conversion runs locally in your browser — nothing is uploaded.

SI and European specs use lux; US lighting plans often use foot-candles. The exact factor:

fc = lux ÷ 10.7639  ·  lux = fc × 10.7639

Searches like lux to foot candle, foot candle to lux, lux to fc, and lux converter all use this relationship. Quick anchors: 1 fc = 10.76 lux · 100 lux ≈ 9.29 fc · 300 lux ≈ 27.9 fc (typical office) · 500 lux ≈ 46.5 fc · 1,000 lux ≈ 92.9 fc (detailed bench work).

Use this page as a live lux to foot-candle calculator or foot candles converter when comparing US datasheets to EN 12464 workplace lighting tables quoted in lux.

One foot-candle is one lumen per square foot (lm/ft²). One lux is one lumen per square metre — so a square metre is about 10.76 times larger than a square foot, giving the 10.764 conversion factor.

The phot (ph) is a CGS unit: 1 phot = 10,000 lux = 929 fc. Older photography and photometry texts may quote phot; convert to lux or fc here for modern specs.

Practical illuminance levels (approximate): moonlight ~0.3 lux · living room ~50–150 lux · office 300–500 lux · supermarket ~750 lux · daylight overcast ~10,000 lux · full sun up to ~100,000 lux. These are incident light on a surface — not lamp wattage.

Illuminance (lux, fc) is light arriving at a surface. Luminance (cd/m², nit) is light leaving a surface — what the eye sees as brightness of an object or screen.

Searches like luminance to illuminance conversion and convert illuminance to luminance are not simple unit factors. They depend on geometry and surface properties. For a perfectly diffusing (Lambertian) reflector with reflectance ρ:

L (cd/m²) ≈ E (lux) × ρ ÷ π

Example: 500 lux on a white wall (ρ ≈ 0.8) gives L ≈ 500 × 0.8 / π ≈ 127 cd/m². This tool converts illuminance units (lux ↔ fc ↔ phot) only — not cd/m². For display brightness in nits, you need a luminance conversion or the formula above with known reflectance.

Foot candles to watts converter searches mix illuminance on a surface with electrical power of a lamp. They are related only through lumens, efficacy, and distance:

• Lumens (lm) = watts × luminous efficacy (lm/W) — LED ~80–150 lm/W, incandescent ~15 lm/W
• Illuminance E (lux) = lumens falling on area ÷ area (m²) — depends on fixture and room geometry

You cannot convert fc directly to watts without knowing how many lumens reach the surface and over what area. Convert fc → lux here, then use lighting design software or the inverse-square / utilisation factor for a specific room. Wattage belongs on lamp datasheets; lux and fc measure result on a work plane.

Occupational standards (e.g. EN 12464, IES recommendations) specify minimum lux for tasks: corridors ~100 lx, general office 500 lx, technical drawing 750 lx, precision assembly 1,000 lx. US documents in foot-candles divide the lux target by 10.764 — this illuminance converter does that instantly.

Photographers sometimes refer to EV (exposure value) and scene brightness; incident light meters often read in lux or fc. Converting between lx and fc keeps exposure notes consistent when switching between metric and imperial equipment manuals.

For LED strip specs quoted in lm/m combined with mounting height, calculated lux at a surface still requires beam angle and distance — unit conversion of the final lux or fc value is what this tool provides.

This tool converts between lux, foot-candle, and phot using standard factors. It does not convert:

• Luminance (cd/m², nit, stilb) — brightness of emissive/reflective surfaces
• Luminous flux (lumens) or luminous intensity (candela) without area geometry
• Electrical watts or colour temperature (K)

For lux to foot candle, foot candle to lux, phot to lux, and general illuminance unit conversion, use the dropdowns above — accurate, client-side, and free.