Foot-Candles to Lux Converter
Enter an illuminance value in foot-candles and get the equivalent in lux — the SI unit used in international lighting standards, architectural specifications, and photometry reports.
Exact conversion
The foot-candle to lux relationship is fixed by definition: one square metre contains exactly 10.763910… square feet, making the conversion factor a precise constant, not an approximation.
One reading, one point
Illuminance varies across a surface and with distance from the source. A single meter reading tells you the level at that spot — not the average for the whole room.
What is a foot-candle?
The US imperial unit of illuminance
A foot-candle (symbol: fc) is the US and imperial measure of illuminance — the luminous flux per unit area falling on a surface. One foot-candle equals one lumen per square foot. It is the unit found in US building codes, OSHA regulations, and theatrical and photographic lighting specifications. Lux (lx) is the equivalent SI unit: one lux equals one lumen per square metre. Since a square metre is larger than a square foot, one foot-candle is a larger unit of illuminance than one lux.
Enter your foot-candle reading to get the lux equivalent instantly — useful when working with international lighting standards or comparing measurements from different systems.
Because a square metre is larger than a square foot, one foot-candle represents a greater illuminance than one lux. The exact conversion factor comes from the definition of the foot: 1 ft = 0.3048 m, so 1 ft² = 0.09290304 m², and 1 fc = 1 lm/ft² = 1/0.09290304 lm/m² ≈ 10.7639 lx. To convert foot-candles to lux, you multiply by this factor.
lux = fc × 10.7639To go in the other direction — lux to foot-candles — divide by 10.7639. The full constant is 10.763910416709722, derived from the exact SI definition of the foot.
Knowing the lux value is most useful when you compare it against established reference levels. According to the Illuminating Engineering Society (IES) and international lighting guidelines, a dim residential corridor needs around 4–5 fc (about 50 lux), while a living room for general tasks sits at 9–19 fc (100–200 lux). Office and school environments typically require 30–50 fc (300–500 lux) at the task surface to support sustained reading and writing without eye strain.
Retail and supermarket floors are commonly specified at around 70 fc (750 lux) to make merchandise colours vivid and appealing. An overcast outdoor sky provides roughly 90 fc (1 000 lux), a bright cloudy day around 929 fc (10 000 lux), and direct sunlight on a clear summer day can reach 9 000 fc (100 000 lux) or more. Film and photography studios in the US report in foot-candles because older equipment and industry standards were built around the imperial system. If your lighting code specifies lux and your meter shows foot-candles, this converter gives you the exact value to verify compliance.
This calculator converts the unit only — it does not measure or estimate the actual illuminance in your space.
A single reading captures one point in space
Illuminance falls off with the square of the distance from the light source and varies significantly across a room or work surface. Lighting standards specify maintained average illuminance levels, not the peak at one spot. For compliance verification, take multiple readings across the task area and average them according to the relevant standard (IES, EN 12464, or local code).