Lux to Footcandles Calculator

About the Lux to Footcandles Calculator

A lux to footcandles calculator converts international SI illuminance measurements in lux to US customary footcandles for use in American lighting standards, IES recommendations, OSHA compliance, and architectural specifications. The conversion is simple and exact: 1 lux = 0.09290 footcandles (or equivalently, 1 footcandle = 10.764 lux). Despite nearly universal global adoption of the SI system, the United States lighting industry, theatrical community, and building codes continue to use footcandles as the primary unit of illuminance. When a lighting designer in Europe or Australia delivers a photometric report using lux, or when luminance measurements from a European light meter need to be interpreted for a US client or specification, the lux-to-footcandles conversion is essential. Our calculator converts any lux value to footcandles with accompanying reference values showing what common footcandle levels mean in practice — from minimum emergency egress requirements to full surgical theatre illumination. The footcandle result is immediately applicable to IES Lighting Handbook recommendations, LEED v4 lighting credits, and OSHA workplace lighting regulations.

How It Works

Footcandles = Lux / 10.764 = Lux × 0.09290. The exact mathematical relationship: 1 lux = 1 lm/m²; 1 fc = 1 lm/ft²; since 1 m² = 10.7639 ft², 1 lux = 1/10.7639 fc = 0.09290 fc. Examples: 100 lux = 9.3 fc; 300 lux = 27.9 fc; 500 lux = 46.5 fc; 750 lux = 69.7 fc; 1,000 lux = 92.9 fc; 10,000 lux = 929.0 fc. IES recommendations in footcandles for reference: hallways and corridors: 5-10 fc; residential living: 10-20 fc; offices (general): 30-50 fc; reading and detailed work: 50-75 fc; retail merchandise display: 50-100 fc; surgical: 200 fc+. Converting these to lux: 30 fc = 322.9 lux; 50 fc = 538.2 lux; 75 fc = 807.3 lux.

Tips & Best Practices

• ✓LEED v4 lighting requirements: ASHRAE 90.1 (referenced by LEED) specifies maximum lighting power densities in W/ft², not footcandles. However, LEED EQ credit for interior lighting requires minimum maintained 25 fc (270 lux) at task areas and maximum 500 fc (5,400 lux) to avoid glare. The lux-to-fc conversion is needed when photometric reports are submitted in SI units.
• ✓Photography setups: incident light meters on professional sets read in either lux or footcandles depending on the meter model and user preference. Converting between systems: 100 lux = 9.3 fc. A cinema standard of 500-1,000 lux = 46.5-92.9 fc. Cinematographers typically aim for 4-8 fc base exposure in controlled studio settings.
• ✓Canadian lighting standards: Canada uses both systems — SI (lux) in national standards and engineering specifications, footcandles in some US-influenced commercial specifications. Understanding both and the conversion factor is important for pan-North American projects.

Who Uses This Calculator

European and international lighting engineers translating photometric reports to US footcandle standards for American clients. Architects verifying that a lighting design meets IES recommendations expressed in footcandles. US-based designers receiving lux-based photometric data from international fixture manufacturers. LEED project coordinators converting measured lux levels to footcandles for credit documentation.