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Foot Candles Formula:
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Foot candles (fc) is a unit of measurement for illuminance, representing the amount of light falling on a surface. It calculates the luminous flux (lumens) per unit area, providing a measure of how well a space is illuminated for various activities and tasks.
The calculator uses the foot candles formula:
Where:
Explanation: This formula calculates the illuminance level by dividing the total light output (lumens) by the area being illuminated, giving you the light intensity per square foot.
Details: Proper lighting levels are essential for visual comfort, productivity, safety, and energy efficiency. Different activities require different foot candle levels - from 10-20 fc for general ambient lighting to 50-100+ fc for detailed tasks like reading or assembly work.
Tips: Enter the total lumens from your light source(s) and the area of the room in square feet. Both values must be positive numbers. The calculator will determine the foot candle level for proper lighting assessment.
Q1: What are typical foot candle requirements for different spaces?
A: Living rooms: 10-20 fc, Kitchens: 30-40 fc, Offices: 30-50 fc, Reading areas: 50-75 fc, Detailed work: 75-100+ fc.
Q2: How do foot candles relate to lux?
A: 1 foot candle = 10.764 lux. Foot candles are imperial units while lux are metric units for illuminance.
Q3: Why is foot candle calculation important in lighting design?
A: It ensures adequate lighting for tasks, prevents eye strain, improves safety, and helps optimize energy usage by avoiding over-lighting.
Q4: How do I measure existing foot candles in a room?
A: Use a light meter (illuminance meter) placed at the work surface height to measure actual foot candle levels in different areas of the room.
Q5: What factors affect foot candle calculations?
A: Room surface reflectivity, light fixture efficiency, mounting height, beam angle, and light loss factors all impact the actual illuminance levels.