Lighting Fixtures Count by Area Calculator

Design lighting across multiple rooms with precise planning and checks for uniformity. Pick fixtures from libraries or enter custom lumens and watts per model. Choose code editions to load target illuminance presets by space type quickly. Set spacing criteria, mounting height, and utilization or losses assumptions. Export CSV and PDF reports with totals easily.

Inputs
Room length.
Room width.
Finished ceiling height.
Typical 0.8 m for desks.
Choose lux or foot-candles (1 fc = 10.764 lux).
Loads typical targets by space. Verify with current standards for your project.
Manufacturer nominal output per luminaire.
Used to estimate connected load.
Select a preset to auto-fill lumens, watts, CU, and SC.
From photometric data; typical 0.5–0.8.
Accounts for dirt, aging; typical 0.7–0.9.
From photometrics; typical 1.2–1.5.
Affects rows/columns approximation.
Quick Presets
office 500 lx classroom 400 lx retail 700 lx warehouse 200 lx corridor 100 lx
Click a tag to set typical illuminance.
Derived
Area, mounting height, and maximum spacing will update after calculation.
    Single-Room Results
    Area (m²) Target (lux) Fixture Lumens CU LLF Required Fixtures Rows × Cols Spacing L × W (m) Avg Achieved (lux) Total Load (kW)
    No results yet.
    Batch — Multi-Room Summary

    Add multiple rooms from the current inputs. Totals and weighted averages are computed.

    # Label L × W (m) Area (m²) Target (lux) Lumens CU LLF Fixtures Rows × Cols Load (kW)
    No rooms added yet.
    Totals 0.00 — 0 0.00
    Example Data
    UseL (m)W (m)Ceil (m)Target luxLumensCULLFSCLoad W
    Open office18123.050040000.650.801.2032
    Classroom1083.050036000.600.851.2528
    Retail20103.675050000.700.801.4040
    Warehouse30188.0200120000.550.801.50110
    Corridor122.52.710015000.600.851.1012
    Formula Used

    The required number of luminaires is computed from the lumen method:

    N = ceil( (A × E) / (F × CU × LLF) )
    • A — Area of the space in square meters.
    • E — Target illuminance on the workplane (lux). If input is foot-candles, it is converted to lux (1 fc = 10.764 lux).
    • F — Lumens per fixture.
    • CU — Coefficient of Utilization, from luminaire photometrics.
    • LLF — Light Loss Factor, product of maintenance factors.

    Layout approximation assumes an evenly spaced rectangular grid. Rows and columns are selected to fit the room aspect ratio. Spacing is checked against the maximum recommended spacing:

    MH = ceiling height − workplane height
Max spacing = SC × MH

    Average achieved illuminance is estimated as:

    E_avg = (N × F × CU × LLF) / A
    These are planning estimates. For critical applications, perform detailed photometric analysis.
    How to Use
    1. Enter room dimensions and select units.
    2. Pick a luminaire from the library or type custom data.
    3. Optionally choose a code edition and space type preset.
    4. Set CU, LLF, SC, and layout preference.
    5. Click Calculate for single-room results, then add to batch.
    6. Export CSV or PDF for single-room or batch summaries.
    FAQs

    Use the luminaire’s photometric report. CU depends on room surfaces and distribution. LLF combines factors like lamp lumen depreciation and dirt depreciation; many designs assume 0.70–0.90.

    Yes. Choose foot-candles in the dropdown. The calculator converts foot-candles to lux using 1 fc = 10.764 lux.

    It is an even-grid approximation based on the room aspect ratio. For final aiming, spacing, and glare control, use detailed lighting design software and manufacturer photometrics.

    Increase the number of fixtures, choose luminaires with a higher spacing criterion, or adjust mounting height and layout to reduce spacing distances.

    Presets load typical planning values for space types. They are guidance only; confirm against the latest standard or project specification applicable to your jurisdiction.
    Notes

    This tool uses planning-level calculations. Verify with standards relevant to your project and jurisdiction.

    • Lux targets vary by task and space type.
    • Surface reflectances impact CU; brighter rooms use fewer fixtures.
    • Maintenance schedules affect LLF; dirtier environments need higher allowance.
    • Grid shown is conceptual; aisle and obstruction coordination may change counts.

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