About the Foot-Candles to Lux Converter
This illuminance converter switches between foot-candles, the unit used in US lighting design and on many light meters, and lux, the SI unit used in most of the world and in international standards. It also covers kilolux (common for sunlight and plant-growing meters), phot, milliphot, lumens per square inch and nox for very dim light.
Use it when a lighting spec, grow-light chart or photography guide uses a different unit from your meter, when comparing a US office lighting target with a European one, or when checking whether a space is bright enough for the task. A foot-candle is one lumen spread over one square foot; a lux is one lumen over one square metre, so one foot-candle is about 10.76 lux.
Illuminance measures light falling on a surface. It is not the same as luminous flux (lumens, the total output of a lamp) or luminance (how bright a surface looks, in cd/m²) — use the lux-to-lumens tool if you need to go from a target light level to lamp output.
How to use the foot-candles to lux converter
- 1Enter the illuminance reading or specification.
- 2Select the unit it is in, for example foot-candles.
- 3Select the unit you need, for example lux.
- 4Read the result, the full table of units and the typical light level it matches.
Formula and method
All illuminance units are lumens divided by an area, so converting between them is just a ratio of areas. One square foot is exactly 0.09290304 m² (because 1 ft = 0.3048 m), so one lumen per square foot equals 1 ÷ 0.09290304 = 10.7639104 lumens per square metre. To convert foot-candles to lux multiply by 10.764; to convert lux to foot-candles multiply by 0.0929.
The phot is the old CGS unit of one lumen per square centimetre (10,000 lux), a milliphot is 10 lux, one lumen per square inch is 1 ÷ 0.00064516 m² = 1,550.0031 lux, and the nox is a millilux. The converter multiplies your value by the lux in the source unit and divides by the lux in the target unit.
- lx
- Lux, one lumen per square metre (SI)
- fc
- Foot-candle, one lumen per square foot
- ph
- Phot, one lumen per square centimetre
Worked examples
50 foot-candles office target in lux
50 × 10.7639 = 538.2 lux, which is a typical illuminance for general office work — the same as 0.538 kilolux.
500 lux in foot-candles
Multiply by 0.09290304: 500 × 0.0929 = 46.45 foot-candles. European guidance written in lux translates to roughly 46 fc on a US meter.
Direct sunlight, 100,000 lux
100,000 × 0.09290304 = 9,290 foot-candles. Since a phot is 10,000 lux, the same light is 10 phot.
Frequently asked questions
How many lux are in a foot-candle?+
One foot-candle equals 10.7639 lux, because a square foot is 0.0929 square metres. Many people round to 10 or 10.76 for quick estimates.
How do I convert lux to foot-candles?+
Divide lux by 10.764, or multiply by 0.0929. For example, 300 lux ÷ 10.764 = 27.9 foot-candles.
What is the difference between lux and lumens?+
Lumens measure the total light a source emits. Lux measures how much of that light lands on each square metre of a surface. The same 1,000-lumen lamp gives 1,000 lux over 1 m² but only 100 lux spread over 10 m².
How bright is 1,000 lux?+
About 1,000 lux is a brightly lit workspace or an overcast day near a window. Typical indoor rooms are 100–500 lux, while direct midday sunlight can exceed 100,000 lux.
Is a foot-candle related to candela?+
Historically a foot-candle was the light one standard candle cast on a surface one foot away. Today it is defined purely as one lumen per square foot; candela is a separate unit of luminous intensity.