Lux to Foot-Candles Converter (and Foot-Candles to Lux)

How it works

fc = lx × 0.09290304 = lx ÷ 10.7639 · lx = fc × 10.7639 · 1 klx = 1,000 lx · 1 ph = 10,000 lx · 1 nx = 0.001 lx · from lumens: fc = lm ÷ ft², lx = lm ÷ m²

Lux and foot-candles both measure illuminance, the amount of light landing on a surface. One lux is one lumen spread over a square meter, and one foot-candle is one lumen spread over a square foot. A square foot is 0.09290304 m², so a foot-candle is about 10.76 times brighter than a lux: divide lux by 10.7639 (or multiply by 0.0929) to get foot-candles, and multiply foot-candles by 10.7639 to get lux. The conversion is exact, because the foot is defined as exactly 0.3048 m. US lighting codes and the OSHA construction standard give light levels in foot-candles, while light meters, European standards and most of the world use lux, so the same rule of thumb appears in both. The calculator also converts to kilolux (daylight meters), phot (lm/cm², an old CGS unit) and nox (millilux, for night vision). In "Lumens and area" mode it gives the average illuminance from a known light output; under More options you can reduce it for light lost to walls and fixtures. The table compares your level with OSHA minimums and typical settings. For the exposure value used in photography, use the lux to EV calculator; for light from a lamp at a distance, use the illuminance inverse-square calculator.

Worked example

A light meter reads 500 lx on an office desk. 500 × 0.09290304 = 46.452 foot-candles, which is above the OSHA minimum of 30 fc for offices. In reverse, 30 fc × 10.7639 = 322.92 lx. With 3,000 lumens spread evenly over a 120 sq ft room, the average is 3,000 ÷ 120 = 25 fc, or 269.1 lx.

Sources: RapidTables: Lux to foot-candles conversion (× 0.09290304) · OSHA 29 CFR 1926.56, Table D-3: Minimum illumination intensities in foot-candles · Wikipedia: Lux (typical illuminance levels, phot and nox) · Wikipedia: Foot-candle

Frequently asked questions