How the lighting calculator works
Estimate the room’s target light output using a chosen illuminance level. Choose Metric or Imperial and enter measurements in the units shown. The calculation uses a simple geometric or cost model and adds an allowance where appropriate.
Worked example
Try room length (ft): 14, room width (ft): 12, and target lumens per sq ft: 20. The calculator above starts with these values so you can reproduce the result and change each input to match your project.
Before you buy materials
Measure at more than one point, note doors and openings, and verify the specifications of your chosen products. Complex layouts, uneven surfaces and installation methods can change the actual quantity required. Keep your measurements and request a supplier or contractor quote for larger jobs.
Frequently asked questions
Is this estimate exact?
No. It is a planning estimate based on the measurements and assumptions you provide. Actual quantities and costs vary by product and installation conditions.
Should I buy extra material?
Many projects need extra material for cutting, breakage or mistakes. The result explains whether an allowance is included. Check your supplier’s recommendations.
Can I use metric measurements?
Yes. Choose Metric or Imperial above. Your measurements and the relevant results are converted automatically.