What is the difference between foot-candles and lux?

Both foot-candles (fc) and lux (lx) measure illuminance - how much light falls on a surface. Foot-candles are imperial units used primarily in the US (1 fc = 1 lumen/ft²), while lux is the SI metric unit used internationally (1 lx = 1 lumen/m²). The conversion is 1 fc = 10.764 lux.

When should I use foot-candles vs lux?

Use foot-candles when working with US standards (IES Lighting Handbook, OSHA requirements) or US-based projects. Use lux for international projects, European standards (EN 12464-1), or ISO specifications. Most modern lighting software supports both units, but always match the unit system to your project's standard requirements.

What are typical illuminance levels for offices?

Office lighting standards recommend: general office space 30-50 fc (300-500 lux), computer work areas 50 fc (500 lux), conference rooms 30-50 fc (300-500 lux), lobbies and corridors 10-20 fc (100-200 lux). IES and EN 12464-1 provide detailed recommendations by task type.

Why is 10.764 the conversion factor?

The factor 10.764 comes from the relationship between square feet and square meters. Since 1 foot = 0.3048 meters, 1 square foot = 0.0929 square meters. When you divide lumen/ft² by lumen/m², you get 1/0.0929 = 10.764. This is an exact mathematical conversion based on the meter-foot relationship.

How do I measure illuminance in the field?

Use a lux meter (illuminance meter) placed at the task surface with the sensor facing up. Take multiple readings across the space and calculate the average. Most meters display in lux; multiply by 0.0929 for foot-candles. Ensure the sensor isn't shaded by your body or objects during measurement.

What illuminance is safe for working?

OSHA recommends minimum 10 fc (100 lux) for general work areas and 30 fc (300 lux) for detailed work. However, safety and comfort require different levels: warehouses need 20-30 fc (200-300 lux), manufacturing 30-100 fc (300-1000 lux), and precision work 100-200+ fc (1000-2000+ lux).

Foot-Candles to Lux Converter

Convert between foot-candles (US) and lux (metric) illuminance units. Compare against IES and EN lighting standards for various applications.

IES StandardsEN 12464-1

Input Parameters

Enter illuminance value in foot-candles or lux to convert