What inputs affect the result the most?

Lumens per fixture, mounting height, fixture count, and room size. Beam angle and surface reflectances strongly affect real-world uniformity and comfort.

Recessed Lighting Calculator (Spacing, Layout, Lux/Foot-Candles) | Stetra Lighting

Recessed Lighting Calculator (Spacing, Layout, Lux/Foot-Candles)

Use this recessed lighting calculator to estimate downlight spacing, offsets from walls, and a clean ceiling grid layout. It also provides a rough lux/foot-candle estimate based on room size, mounting height, and lumens per fixture.

Spacing + wall offsets Layout preview grid Metric + Imperial

Calculator

First approximation

Metric / Imperial

Room Dimensions

Enter room size and mounting height (fixture to work plane).

Width

Length

Mounting Height

Fixture Layout

How many lights do you place along each direction?

Lights in X-direction

Lights in Y-direction

Fixture Data

Use lumens from your spec sheet and a reasonable maintenance factor.

Lumens per Light

Maintenance Factor (MF)

Note: This calculator gives a first approximation. For accurate and professional results, use a photometric plan (IES-based) that includes reflectances, geometry, and fixture optics.

What this calculator does

Estimates fixture count for basic illumination planning.
Shows approximate spacing based on room dimensions.
Previews a simple ceiling grid for symmetry and flow.
Lets you test different quantities without manual math.

Works for more than recessed lights

Use it for recessed downlights, surface fixtures, and most ceiling-mounted luminaires where spacing is the main question.

When you need a full photometric plan

If you need verified lux/fc targets, code compliance, or coordination across multiple fixture types, photometry provides accuracy this calculator cannot.

Order Photometric Plan

Stetra Lighting delivers permit-ready reports using real IES files and your project requirements.

Practical layout tips

Group by zones (kitchen task, seating, circulation, accent walls).
Avoid clutter — too many fixtures too close can increase glare.
Match spacing to beam angle for smoother distribution.
Include dimming for flexibility and comfort.
Coordinate other fixtures (pendants, wall washers, sconces).

How to use the recessed lighting calculator

Steps

Enter room dimensions (length and width).
Add mounting height for better scale and proportions.
Set fixture quantity in X and Y to test spacing options.
Review layout and spacing for symmetry and flow.
Adjust as needed, then verify with photometry when accuracy matters.

Use this as a planning guide

Final placement depends on fixture type, beam angle, finishes, ceiling details, obstructions, and the actual IES distribution.

Is the illuminance result accurate?

It’s a first approximation. Accurate lux/fc values require a photometric calculation using the actual IES file and room geometry.

Related tool: Lumen Calculator →

What affects uniformity and glare?

Fixture optics, beam angle, spacing, mounting height, and surface reflectances all influence uniformity and glare.

Related tool: IES Viewer →

When should I order a photometric plan?

When you need verified targets, code compliance, glare evaluation, or documentation for permitting and construction.

Related tool: Lighting Services →