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Recessed Lighting Layout Calculator — result sheet
Estimate a regular recessed-light layout from room dimensions, a maximum spacing, edge margin, target illuminance, fixture lumens, and utilization assumptions.
Inputs used
Results
Visual chart
Breakdown
Calculation steps
Returned data table
Formula and methodology
Formula: Available length = room length − 2×edge margin; intervals = ceiling(available length/max spacing); layout positions = intervals + 1; lumen-based minimum = ceiling(room area×target lux ÷ (fixture lumens×utilization×maintenance)); recommended fixtures = max(length positions×width positions, lumen-based minimum).
The layout count protects the entered maximum spacing, while the lumen check makes a separate brightness assumption visible. The result is a regular planning grid, not a photometric design: beam angle, ceiling height, wall reflectance, task lighting, dimming, glare, obstructions, and local electrical requirements need a real lighting review.
This result follows the calculator's declared inputs, precision, validation boundaries, and model limits.
Input contract
- Room length — m; minimum 0.1; maximum 10000
- Room width — m; minimum 0.1; maximum 10000
- Maximum center-to-center spacing — m; minimum 0.1; maximum 1000
- Edge margin to first row — m; minimum 0; maximum 1000
- Target illuminance — lux; minimum 1.0E-6; maximum 1000000
- Lumens per fixture — lm; minimum 1.0E-6; maximum 100000000
- Utilization factor — %; minimum 1.0E-6; maximum 100
- Maintenance factor — %; minimum 1.0E-6; maximum 100
Worked example
| Input | Value |
|---|---|
| Room length | 5 |
| Room width | 4 |
| Maximum center-to-center spacing | 1.8 |
| Edge margin to first row | 0.6 |
| Target illuminance | 300 |
| Lumens per fixture | 1000 |
| Utilization factor | 60 |
| Maintenance factor | 80 |
The layout uses 4 by 3 positions, or 12 fixtures; the simplified lumen check requires 13, so the planning recommendation is 13 fixtures.
Assumptions and limits
- Room dimensions and spacing use metres, and the room is treated as a rectangle.
- The first and last rows are placed at the entered edge margin and the remaining intervals are evenly distributed.
- The spacing field is a planning maximum, not a manufacturer’s beam-spread limit.
- Illuminance uses area times target lux as a simplified lumen requirement.
- Utilization and maintenance factors are entered as percentages and are multiplied with fixture lumens.
- The recommended count is the larger of the geometric grid count and the simplified lumen count.
- The calculator does not choose fixture placement over joists, insulation, wet locations, fire ratings, wiring, controls, or code requirements.
Calculator note
Source and methodology
Use the official WorldCalculate methodology policy for the source, formula, precision, and boundary standards behind this calculator.
Planning estimate, not financial, medical, legal, or professional advice. © WorldCalculate — reuse with attribution. Built and curated by Hassan ALRowaie.
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