Is this the same as a full photometric study?

No. It is a practical planning model for coverage and relative brightness. For critical commercial specs, use manufacturer IES data and professional lighting design tools.

Can I plan multiple lights?

Yes. Choose a fixture count and review the combined coverage in both the 3D view and the heatmap.

Does furniture block light?

Tall pieces block spill in real rooms. Use the 3D scene as a reminder to leave margin near shelves and wardrobes, and treat open-floor heatmaps as optimistic.

What does the target lux setting do?

It sets the pass threshold for “area above target.” It does not change how bright the lamps are, only how much of the floor meets your goal.

Why is my average lux low with few lamps?

Lux falls quickly with distance. A single low-lumen lamp in a large room will show modest averages and small zones above a high target. That is expected.

Should I match shop lumen labels exactly?

Use manufacturer lumen ratings as a starting point, and remember real rooms have reflectance, shades, and dirt that reduce delivered light over time.

Lighting Coverage Calculator

Set room size, fixture count, and lamp output, then switch between a 3D preview and a lux heatmap. Bright pools and dim corners show up before you buy fixtures or lock wiring positions.

Helpful for living rooms, bedrooms, studios, and small offices when you are deciding how many lights you need and where they should sit. Treat the model as a planning aid, then confirm critical work lighting with manufacturer lumen ratings on site.

If area above target reads 0%, peak lux may simply be below your goal. Raise output, add fixtures, or lower the target to match how the room is used.

Photometric planning model

The heatmap and 3D floor share the same lux field (direct beam + optical spill + room bounce). Fixed residential exposure (no auto-gain) keeps dim schemes looking dim. Ceiling downlights use inverse-square falloff and Lambert floor incidence; bounce approximates wall and ceiling interreflection.

Room width (m)Room length (m)Ceiling height (m)Number of lightsLumens per lightBeam angle (degrees)Target average lux

Average illuminance9.99 lux

Peak illuminance48.1 lux

Uniformity min/avg0.38

Area above target0.0%

Recommended target lux148 lux

Room index (K)1.28

No floor area reaches the selected target. Peak illuminance is 48.1 lux, which is 102 lux below target.

Recommended lux follows a residential baseline (~150 lux) adjusted by room index geometry K = (L*W)/(Hm*(L+W)), where Hm is luminaire-to-working-plane height. This gives a geometry-aware target for planning.

About Lighting Coverage Calculator

What this tool does

The Lighting Coverage Calculator helps you plan how light spreads across a room. Set room size, fixture count and layout, and lamp output, then compare a 3D view with a lux heatmap so bright spots and dim corners are easier to see.

Use it when planning ceiling lights, pendants, or lamp layouts in living rooms, bedrooms, studios, and small offices before you buy fixtures or commit to wiring positions.

Even coverage matters as much as peak brightness. Overlapping pools can waste fixtures, while dark corners make a room feel smaller. Move lights around until main tasks (reading, cooking prep, desk work) sit in well-lit zones, then refine with real lumen ratings and colour temperature.

Target lux is a planning goal for “how bright is bright enough,” not a change to the physics of the lamps. If average or peak lux sits below your target, increase output, add fixtures, or lower the target to match the room’s use.

For a full walkthrough of lux targets, fixture count, task versus ambient layers, and fixing dark corners, see the guide on planning room lighting coverage.

How to use it

1Set room width, length, and ceiling-related inputs to match your space.
2Choose how many fixtures to model and review the symmetric layout the tool places.
3Set lumens (and related controls) to match the lamps you are considering.
4Switch between 3D and heatmap views to judge both look and coverage.
5Compare average, peak, and area-above-target metrics while you move furniture or change lamp count.
6Account for tall furniture that will block spill in the real room, even if the open-plan overlay looks clear.
7Finalise a layout that lights tasks first, then fills ambient gaps.

Practical tips

Task lighting (desk, reading chair) usually needs higher local lux than general circulation.
Tall bookcases and wardrobes cast real shadows. Leave margin near them.
Warm white often feels cosier in living rooms; cooler light can help detail work in offices.
If area above target is 0%, peak lux may simply be below your target. Raise lumens or lower the goal.

Frequently asked questions

Is this the same as a full photometric study?: No. It is a practical planning model for coverage and relative brightness. For critical commercial specs, use manufacturer IES data and professional lighting design tools.
Can I plan multiple lights?: Yes. Choose a fixture count and review the combined coverage in both the 3D view and the heatmap.
Does furniture block light?: Tall pieces block spill in real rooms. Use the 3D scene as a reminder to leave margin near shelves and wardrobes, and treat open-floor heatmaps as optimistic.
What does the target lux setting do?: It sets the pass threshold for “area above target.” It does not change how bright the lamps are, only how much of the floor meets your goal.
Why is my average lux low with few lamps?: Lux falls quickly with distance. A single low-lumen lamp in a large room will show modest averages and small zones above a high target. That is expected.
Should I match shop lumen labels exactly?: Use manufacturer lumen ratings as a starting point, and remember real rooms have reflectance, shades, and dirt that reduce delivered light over time.

Related guide

Dig deeper in Plan room lighting coverage: lux, fixtures, and dark corners. Set a lux target for how you use the room, choose fixture count and layout, separate task from ambient light, and fix dark corners before you buy lamps or commit to wiring.

Or browse all ToolzWorx guides.

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