Lighting Foot-Candle Calculator
Estimate foot-candles from fixture lumens, fixture count, and floor area — includes PASS/FAIL compliance when a target illumination level is set.
Lighting Details
lm
qty
sq ft
FC
Live Results
Foot-Candles (FC)
30.00FC
PASSTarget: 30.00 FC
Total Lumens
6,000lm
Lumens per Fixture
1,500lm
Fixture Count
4
Area
200sq ft
Lighting calculations are based on standard foot-candle formulas. Always verify final design with local building codes and lighting standards.
How to Use This Lighting Foot-Candle Calculator
- Enter lumens per fixture. Input the rated lumen output for each light fixture from the manufacturer specification or lamp label. LED troffers typically range from 1,500 to 4,000 lumens; high-bay fixtures may exceed 15,000 lumens. Use delivered lumens after fixture efficiency losses when available.
- Set fixture count. Enter the total number of fixtures illuminating the space. Include all active fixtures in the calculation area — omit fixtures outside the room boundary or on separate circuits serving other spaces.
- Enter floor area. Input the illuminated floor area in square feet. For rectangular rooms, multiply length by width. For irregular layouts, break the space into sections and sum the areas. Use the horizontal work-plane area, not wall surface area.
- Set target foot-candles (optional). Enter the required illumination level for your space type to enable PASS/FAIL compliance checking. Common targets include 30 FC for general office work, 50 FC for retail sales floors, and 10–20 FC for warehouse aisles. Leave blank to calculate foot-candles without a compliance check.
- Review results and adjust design. The results panel shows total lumens, calculated foot-candles, and a PASS/FAIL badge when a target is set. If illumination is too low, increase fixture count or select higher-lumen fixtures. Compare results against IES lighting recommendations and local building code before finalizing the design.
Formulas & Example
Foot-candle level is calculated by dividing total lumens from all fixtures by the illuminated floor area. This simplified formula assumes uniform light distribution across the space — actual measured levels may vary with fixture spacing, mounting height, and reflectance.
Total Lumens = Lumens per Fixture × Fixture Count
Foot-Candles (FC) = Total Lumens / Area (sq ft)
If target FC is set:
PASS when calculated FC ≥ target FC
FAIL when calculated FC < target FCWorked Example
Four LED troffers at 1,500 lumens each illuminating a 200 sq ft office with a 30 FC target:
Lumens per fixture = 1,500 lm
Fixture count = 4
Area = 200 sq ft
Target = 30 FC
Total Lumens = 1,500 × 4 = 6,000 lm
FC = 6,000 / 200 = 30.00 FC
Result: PASS (30 FC ≥ 30 FC target)Use this result alongside the Load Calculation Tool, Breaker Size Calculator, and Wire Gauge Calculator when planning the electrical circuit for new lighting installations.
Frequently Asked Questions
What is a foot-candle?â–¾
A foot-candle (FC) is a unit of illuminance measuring how much light falls on a one-square-foot surface from a one-candela source one foot away. One foot-candle equals approximately 10.764 lux. It is the standard measurement used in North American lighting design to specify how brightly a workspace, retail floor, or industrial area is lit at the work plane.
How many foot-candles do I need?â–¾
Required foot-candles depend on the space type and task performed. IES recommendations include 30–50 FC for general office work, 50–100 FC for detailed drafting or inspection tasks, 20–30 FC for retail sales areas, 10–20 FC for warehouse storage aisles, and 5–10 FC for parking garages. Always verify against the specific IES Lighting Handbook recommendation for your application and any local code requirements.
What is the difference between lumens and foot-candles?â–¾
Lumens measure total light output from a source — how much light a fixture produces in all directions. Foot-candles measure illuminance at a surface — how much of that light actually reaches a given area. Lumens describe the fixture; foot-candles describe the lit environment. Converting between them requires knowing the illuminated area and how light is distributed across that space.
How does fixture count affect lighting?â–¾
Foot-candles increase proportionally with fixture count when lumens per fixture and area remain constant. Doubling the number of fixtures doubles total lumens and doubles the foot-candle level on the floor. In practice, adding fixtures also improves uniformity and reduces shadows, so the perceived quality of lighting improves beyond the raw FC number alone.
What are typical lighting standards?â–¾
Common lighting standards include IES (Illuminating Engineering Society) recommended practice for commercial and industrial spaces, OSHA workplace lighting minimums for safety, and local building codes that may reference IES levels. Office general lighting typically targets 30–50 FC, manufacturing assembly areas 50–100 FC, and corridors or storage areas 10–20 FC. This calculator provides a planning estimate — final designs should be verified by a lighting designer or engineer.
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