Footcandles to Lux Calculator

About the Footcandles to Lux Calculator

A footcandles to lux calculator converts illuminance from the US customary unit (footcandles, fc) to the international SI unit (lux) using the exact conversion factor: 1 footcandle = 10.7639 lux. While most of the world uses lux for lighting measurements, the United States maintains footcandles in professional lighting standards, architectural specifications, and occupational health regulations. The Illuminating Engineering Society (IES) publishes its lighting recommendations in footcandles; OSHA illumination requirements for workplaces are specified in footcandles; US theatrical lighting designers work in footcandles on set. When international architects, engineers, or manufacturers need to interpret US lighting specifications — or when US professionals work on global projects — this conversion is essential for ensuring specifications are correctly interpreted across standards. Our calculator converts any footcandle value to lux instantly, shows the reverse calculation for spot-checking, and provides a reference table of common US footcandle recommendations alongside their lux equivalents for quick project comparison. The conversion is exact because both units measure the same physical quantity — luminous flux per unit area — using different area units (square feet vs. square metres).

How It Works

Lux = Footcandles × 10.764. The factor comes from the unit conversion: 1 foot = 0.3048 m, so 1 ft² = 0.0929 m². 1 lumen per ft² = 1 lumen per 0.0929 m² = 10.764 lm/m² = 10.764 lux. The relationship is exact by definition. Common conversions: 1 fc = 10.76 lux; 5 fc = 53.8 lux; 10 fc = 107.6 lux; 20 fc = 215.3 lux; 30 fc = 322.9 lux; 50 fc = 538.2 lux; 100 fc = 1,076 lux; 200 fc = 2,153 lux. IES and OSHA footcandle references: OSHA 29 CFR 1926.56 construction sites: first aid 30 fc; warehouses 10 fc; tunnels, shafts 5 fc; general construction 3 fc. IESNA office recommendations: 30-50 fc (300-500 lux) general; 50-75 fc (500-800 lux) detailed visual tasks.

Tips & Best Practices

• ✓OSHA footcandle minimums for US workplaces (29 CFR 1926.56): general construction 3 fc; tunnels/underground 5 fc; warehouses 10 fc; first aid stations 30 fc; offices 30 fc minimum. These are minimums — IES recommends 30-50 fc for productive office work.
• ✓Theatrical lighting conventions: US stagehands and lighting directors specify brightness in footcandles on stage. A typical drama: 75-100 fc on performers at center stage. Rock concert production: 200-500 fc on the performance area. European theatres use lux but the same physical standards apply.
• ✓Photography light meters: some legacy light meters (Weston, Sekonic vintage models) read in footcandles rather than lux. Converting the meter reading to lux allows use of modern exposure calculation formulas: EV = log₂(lux × t_s / 0.65) where t_s is the shutter time and 0.65 is the lens transmission factor.

Who Uses This Calculator

US and international architects comparing IES footcandle recommendations to EN 12464 lux standards. Lighting designers working on international projects who need to translate US specifications to SI units. OSHA compliance officers converting workplace lighting requirements to metric equivalents for multinational facilities. Photographers converting between US footcandle and international lux-based exposure calculations.