Office Lighting Plan Calculator

How this lighting plan calculator works

Office lighting planning starts with a target illuminance level measured in lux, then turns that requirement into a practical fixture plan. This calculator uses room size, workspace type, main task, fixture output, LED efficiency, utilization factor, maintenance factor, and operating hours to estimate maintained lumens, fixture output, LED wattage, fixture count, layout, contractor notes, and energy cost. The goal is to help you move from “how many lumens do I need?” to “how should this office be lit?”

The first step is room area. Enter length and width in meters or feet. If you use feet, the calculator converts square footage to square meters before applying the lux formula. Work-plane lumens equal target lux multiplied by area in square meters: effective lumens = lux × m². For example, a 20 m² office at 500 lux needs 10,000 lumens reaching the work plane. That relationship is linear — double the area or double the lux target and you double the maintained light level required at the desk surface.

Fixture output is usually higher than the work-plane lumen number because real rooms lose light to fixture optics, mounting height, wall reflectance, dirt, aging, and furniture. The advanced planning formula is: required fixture lumens = target lux × area ÷ (utilization factor × maintenance factor). With a typical UF of 0.6 and MF of 0.8, the same 20 m² office at 500 lux needs about 20,800 lumens of fixture output, not just 10,000 lumens at the work plane.

LED wattage is derived from lumens per watt (lm/W), also called efficacy. Divide required fixture lumens by your chosen efficiency to estimate electrical load: watts = fixture lumens ÷ lm/W. A 20,800 lumen fixture-output target at 110 lm/W suggests about 190 watts of LED lighting across the space. Common LED fixtures often range from 80–150 lm/W; higher efficacy reduces power draw but does not remove the need for good spacing and glare control.

Workspace type presets adjust the default lux target and suggest color temperature and CRI (Color Rendering Index) suited to that environment. General and open offices typically target 500 lux at 4000K neutral white. Meeting rooms may use 300 lux with slightly warmer 3500K–4000K light for comfort. Design studios often need 750 lux or more with higher CRI for color-critical work. These presets are starting points — you can override the lux slider to match your own standard or client brief.

Basic mode applies typical office assumptions so non-specialists can get a useful plan quickly. Advanced mode lets you adjust target lux, fixture lumens, LED efficacy, utilization factor, and maintenance factor. A lower UF or MF increases required fixture output because more light is lost before it reaches the work plane. The calculator still does not replace photometric design; it answers the planning question “how much total output do I need?” before you select specific products or layouts.

Fixture count suggestions divide required fixture output by the lumen output of each fixture. The planner also compares common fixture options such as LED panels, downlights, and linear fixtures, then creates simple contractor notes you can copy into a brief. Actual layout depends on ceiling grid, beam angle, dimming needs, and whether you use direct-only or direct/indirect luminaires. Use the calculator output when comparing product specifications, preparing a shopping list, or discussing requirements with an electrician or lighting designer.

This calculator provides an estimate for general planning purposes. Actual lighting performance depends on ceiling height, fixture type, room reflectance, layout, maintenance factors, and installation conditions. For commercial projects, consult a qualified lighting designer or electrician.

Recommended lux levels

The table below summarizes typical illuminance ranges for common workspace types. Values reflect widely cited guidance for general planning — local codes, LEED projects, or client standards may differ. When in doubt, 500 lux is a safe default for routine office tasks; lower levels suit circulation and social spaces, while detail work may need 750 lux or more.

Example calculations

Small home office (3 m × 4 m at 500 lux): Area is 12 m². Work-plane demand = 500 × 12 = 6,000 lm. With UF 0.6 and MF 0.8, required fixture output is about 12,500 lm. At 110 lm/W, estimated LED load is about 114 W before dimming. Several small fixtures or one panel plus task lighting may be more comfortable than one bright point source.

Open plan zone (8 m × 10 m at 500 lux): Area is 80 m². Work-plane demand = 40,000 lm. With UF 0.6 and MF 0.8, fixture output is about 83,300 lm. At 120 lm/W efficient LED, nominal wattage is about 694 W — often delivered by multiple linear runs or panel grids rather than one source.

Design studio (5 m × 6 m at 750 lux): Area is 30 m². Work-plane demand is 22,500 lm; fixture output may be around 46,900 lm with typical loss assumptions. Higher CRI (90+) and 4000K–5000K color temperature help color review. Expect more fixtures or higher-output luminaires than a general office of the same size.

For quick lux-to-lumen checks without room dimensions, use our Lux to Lumens Calculator. To translate total lumens into power draw, follow with the Lumens to Watts Calculator.