Lighting Design Calculator

What this lighting design calculator does

This page helps you answer a practical early-design question: how many lumens and fixtures do I need for this room? Enter room dimensions in feet, choose a planning footcandle target, and apply your assumed coefficient of utilization (CU) and light loss factor (LLF).

Required lumens = (target footcandles x area in ft²) ÷ (CU x LLF)

If you also enter fixture lumens, the calculator rounds up to a whole fixture count and suggests a simple rows-by-columns layout. That spacing output is only a screening aid. Final spacing still depends on the fixture photometrics, spacing criterion, glare control, surface reflectances, and the actual task area.

Use the calculator for the actual room before comparing fixture layouts. The targets and notes below are reference material after the input screen, not a substitute for entering the project dimensions and fixture data.

Common starting targets

These are planning targets, not permit-ready guarantees. Confirm the final criteria against the current project basis, owner requirements, fixture photometrics, and any adopted lighting or workplace rules that apply to the actual site.

How to use the inputs

1. Room length and width: enter the actual floor dimensions in feet.
2. Ceiling height and working plane: use the luminaire mounting height above the task plane, not just the slab-to-slab dimension.
3. Planning target: choose a common starting footcandle level or enter a custom target.
4. CU: use a realistic coefficient of utilization for the room proportions and fixture distribution.
5. LLF: include dirt, aging, and maintenance assumptions honestly.
6. Fixture lumens: enter delivered lumens for one fixture only if you want fixture count and spacing.

Calculator workflow example

Try the open-office preset, then adjust room size, target footcandles, CU, LLF, and fixture lumens to match the project. The result area will calculate required lumens, fixture count, approximate rows and columns, and achieved average footcandles from those inputs.

• Use the preset only as a starting point for the input fields.
• Replace the default dimensions and fixture lumens with the actual room and selected luminaire data.
• Use the calculated fixture count and grid as a preliminary screen before a photometric layout.

What this page does not do

• It does not estimate lighting power density from fake efficacy assumptions.
• It does not replace a photometric layout, AGi32 model, or manufacturer spacing check.
• It does not certify code compliance, glare control, emergency egress performance, or daylight controls.