Lux to Foot-candle Converter
Quickly convert from Lux to Foot-candle.
How to convert
Formula:
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Illuminance measures how much light falls on a surface — the fundamental quantity for lighting design, photography, workplace safety, and horticulture.
Where is it used?
• Workplace & Building Lighting — Standards like EN 12464-1 (Europe) and IESNA (North America) specify minimum maintained illuminance for offices (500 lux), corridors (100 lux), surgical suites (10,000–100,000 lux), and...
Examples:
• 1 footcandle (fc) = 10.764 lux
• 1 lux (lx) = 0.0929 footcandles
Illuminance measures luminous flux incident on a surface area, making it the core quantity for lighting design, visual comfort, safety compliance, photography, and controlled-environment agriculture. Professionals frequently convert between lux (SI), footcandles (imperial), and legacy photometric units when comparing standards, equipment specifications, and field measurements.
Illuminance is the luminous flux incident per unit area of a surface. The SI unit is the lux (lx), equal to one lumen per square metre (1 lx = 1 lm/m²). The US customary unit is the footcandle (fc or lm/ft²): 1 fc = 10.764 lux. The cgs unit phot (ph) (1 lm/cm² = 10,000 lux) is obsolete but appears in older literature. Illuminance is distinct from luminance (how bright a surface looks) and luminous flux (total light emitted by a source).
Where is it used?
- Workplace & Building Lighting — Standards like EN 12464-1 (Europe) and IESNA (North America) specify minimum maintained illuminance for offices (500 lux), corridors (100 lux), surgical suites (10,000–100,000 lux), and other spaces.
- Photography & Cinematography — Exposure meters measure incident illuminance in lux or footcandles to calculate correct camera settings (aperture, shutter speed, ISO). Studio lighting is set and verified with lux meters.
- Horticulture & Controlled Environment Agriculture — Light intensity for plant growth is measured in lux (for general comparison) and PPFD (μmol/m²/s) for precision; conversion between lux and PPFD depends on the spectral quality of the light source.
- Emergency & Safety Lighting — Building codes specify minimum illuminance for escape routes and emergency exits (typically 1–10 lux at floor level) to ensure visibility during power failure.
- Display & Screen Ergonomics — Office ergonomics standards specify maximum ambient illuminance at screen positions to prevent glare and reflections that reduce display readability.
Common Conversion Mistakes
Confusing lux with lumens
Lux (lm/m²) measures light received at a surface; lumens measure total light emitted by a source. A 1,000 lm lamp creates 1,000 lux on a 1 m² surface directly below, but only 100 lux spread over 10 m². Distance and geometry determine illuminance; lumen output alone does not.
Confusing lux with footcandles — the factor of ~10
1 footcandle = 10.764 lux. When reading specifications, a US office standard of 50 fc = 538 lux — not 50 lux. Converting between legacy US standards (fc) and international standards (lux) requires the 10.764 factor, often approximated as ×10 or ÷10 for quick estimates.
Applying illuminance to describe surface appearance
Illuminance tells you how much light hits a surface, not how bright it looks. A black surface and a white surface receiving the same 500 lux have very different luminances. Perceived brightness depends on illuminance × reflectance. For visual comfort analysis, luminance (cd/m²) is more relevant than illuminance.
Ignoring the cosine law and measurement angle
Illuminance on a tilted surface follows the cosine law: E = E₀ × cos(θ), where θ is the angle between the light direction and the surface normal. A surface tilted 60° from the light direction receives only 50% of the horizontal illuminance. Lux meters must be held perpendicular to the measurement surface for accurate readings.
Quick Reference Table
| From | To |
|---|---|
| 1 footcandle (fc) | 10.764 lux |
| 1 lux (lx) | 0.0929 footcandles |
| 1 phot (ph) | 10,000 lux |
| Full moonlight | ~1 lux |
| Sunrise/sunset | ~400 lux |
| Overcast daylight outdoors | ~1,000 lux |
| Direct sunlight | ~100,000 lux |
| Office standard (EN 12464-1) | 500 lux maintained |
Frequently Asked Questions
What is the difference between lux and lumens?
Lumens (lm) measure total luminous flux emitted by a light source — a property of the source. Lux (lm/m²) measures luminous flux received per unit area at a surface — a property of the lit surface at a specific location. A 1,000 lm lamp produces 1,000 lux on 1 m², 250 lux on 4 m², and 111 lux on 9 m². Lux depends on both the source output and the distance and geometry of the installation.
How do I convert footcandles to lux?
Multiply footcandles by 10.764 to get lux. To convert lux to footcandles, multiply by 0.0929. Quick approximation: lux ÷ 10 ≈ footcandles; footcandles × 10 ≈ lux. Example: a US standard of 50 fc for office task lighting = 50 × 10.764 = 538 lux, which aligns with the European EN 12464-1 recommendation of 500 lux for office work.
How much light do plants need, measured in lux?
Low-light houseplants (ferns, pothos): 500–2,500 lux. Medium-light plants (most tropical foliage): 2,500–10,000 lux. High-light plants (cacti, most fruiting vegetables): 10,000–30,000 lux. Full-spectrum outdoor sunlight: ~100,000 lux. For precision horticulture, PPFD (μmol/m²/s) is preferred because lux does not account for the spectral efficiency of different light colors for photosynthesis.
What lux levels are required for different workplaces?
EN 12464-1 and IESNA RP-1 specify: corridors/stairways 100 lux; general offices 500 lux; drafting and detailed assembly work 750–1,000 lux; fine watchmaking and surgical tasks 1,500–10,000 lux. Emergency escape route lighting requires a minimum of 1 lux at floor level (EN 1838). Outdoor sports facilities typically require 200–500 lux for recreational use, 750–2,000 lux for broadcast television.
Sources & Standards
- CIE S 008/E:2001 — Lighting of Work Places (indoor)
- EN 12464-1:2021 — Light and lighting: workplaces indoors
- IES RP-1-20 — Recommended Practice: Office Lighting (North America)
- ISO 8995-1:2002 — Lighting of indoor work places
Reviewed by The Unit Hub Editorial Team · March 2026