Lighting calculators / Downlight planning
Downlight spacing calculator
& layout planner.
Choose a measured downlight, enter your room dimensions and set your spacing preference.
Compare suitable options, then request a quote and product check with your result included.
Measured options.Real photometry · adjustable layouts
02 / Test the layout
Your room, calculated.
Distance between downlights
Measure centre to centre. Wall distances are from the wall to the first fitting’s centre, equal at both ends.
Automatic layouts keep spacing at or below your preference where possible. Whole rows and columns mean the exact distances change in steps; brighter targets or narrower beams can need closer spacing.
How the coverage check works
The tool flags a sampled minimum below 40% of the room average across the whole calculation plane. This is an early planning check, not a task-specific lighting standard. Check the room edges and work areas; reflections and obstructions are excluded.
False colour shows calculated illuminance, not material appearance. Darker blue indicates lower direct illuminance; brighter blue indicates higher direct illuminance. Markers show fitting positions. Reflections, furniture, glare and maintenance are excluded.
Check the light across your room.
Darker blue areas receive less direct light; brighter blue areas receive more. Check for dark gaps where light is needed. Try another beam or adjust the rows and spacing to compare the coverage.
Your selected downlight, quantity, spacing and room dimensions are included in the enquiry.
03 / Compare measured options
Closest products for this room.
Six distinct measured product families are ranked against your room, grid and initial average target. Arc and Pulse remain available in the selector but are not automatic alternatives. “Try in my room” keeps the same layout so the comparison is fair. Switch to Automatic if you want the tool to recalculate the fitting count for the new product.
04 / Keep your result
Take the layout into your project brief.
Save the selected model, quantity, spacing, measured output and calculation assumptions.
05 / Your project
Build the project brief.
Your selected model, quantity, spacing and room dimensions are already included. Add the ceiling details, finish, controls and required date that you know so the enquiry starts with a clear fitting brief.
- Room dimensions
- Preferred fittings
- Project requirements
Review calculation included
How many downlights do I need?
Enter the room dimensions, ceiling height and calculation plane, then choose a measured downlight option. Automatic mode searches up to eight rows and eight columns for the lowest count meeting your spacing preference, initial average target and the tool’s coverage check. If no grid meets all three, it shows a fallback with guidance. You can also set a manual grid. Glare and maintained illuminance are not assessed.
How far apart should downlights be?
Spacing depends on the actual distribution, mounting height and where light is needed. This downlight spacing calculator shows the centres and wall setbacks for your grid. Compare the light between fittings and at the room edges instead of relying on a single spacing rule.
Centre spacing is the distance between neighbouring fittings; a wall setback is the distance from the wall to the nearest fitting centre. At 100% spread, this planner divides the room length by the number of columns and the width by the number of rows, with half that spacing at each wall.
Downlight spacing example: a 6 m by 4 m room
A manual grid of three columns and two rows at 100% spread places six downlights at 2 m centres in both directions, with 1 m wall setbacks. This describes the geometry, not whether six fittings provide enough light. Compare the calculated light levels for your chosen product, ceiling height and working plane before accepting the layout. Reducing the spread brings the fittings closer to the centre of the room.
Can room area alone tell me how many downlights I need?
Area alone does not account for the product output or how its light reaches the room. Use the lighting design calculator for a first whole-room lumen and quantity estimate, then compare actual downlight layouts here. For reception desks, counters or other task areas, check the light where the work happens as well as the whole-room average.
What the calculation includes
Direct light from every fitting is added at 32 × 32 cell-centre samples across the horizontal plane, using the selected LDT file. The average, minimum and maximum are sampled estimates; small bright peaks may fall between points. Each fitting is approximated as a point source at its centre; close distances need a more detailed calculation. The whole-room coverage ratio does not assess uniformity on the actual task areas.
No reflected light, obstructions, maintenance factor, glare or emergency performance is calculated. This is an early layout estimate, not a completed lighting design. View the commercial downlight ranges and confirm the final specification before ordering.
Selected photometric source
Download photometryIndicative planning tool only. Results depend on the information entered and the stated assumptions; actual installed performance may differ. This is not a final lighting design or confirmation of compliance. Have the layout, product suitability and applicable requirements checked by a competent lighting professional before ordering or installation.
LUMENLOOP / LIGHTING TOOLS
Downlight layout estimate
Discuss your specification · info@lumenloop.co.uk · 02045 721 554