Lux & Lumens Calculator
Use our free lighting calculator to estimate how many light fittings a room may need. Enter the room dimensions, choose the type of space, and add the lumen output of one fitting to calculate the approximate total lumens, fitting quantity, and grid spacing.
The tool can be used for bedrooms, living rooms, kitchens, offices, retail showrooms, workshops, warehouses, and other residential or commercial spaces.
Lux & Lumens Calculator
Estimate the total light output and approximate number of fittings required for a rectangular room.
Advanced calculation options
How to Use the Lux & Lumens Calculator
Follow these steps to estimate the number of light fittings required for your room.
1 Select the room or activity
Choose the room or activity that most closely matches your space. The calculator will automatically apply a practical target lux level.
Select Custom lux target when you need to enter a specific project requirement.
2 Enter your room dimensions
Enter the room length and width in metres. The calculator multiplies them to determine the total floor area.
3 Enter the lumens per fitting
Use the lumen output shown in the product specifications. For example, enter 800 for a fitting rated at 800 lumens.
Do not enter wattage in this field. Wattage measures electrical consumption, while lumens measure the amount of visible light.
4 Review the estimated quantity
The result shows the adjusted lumen requirement and the estimated number of fittings. The fitting quantity is rounded up to the next complete number.
The grid spacing is an initial layout reference, not a guaranteed maximum spacing or final lighting plan.
Use the advanced factors
The default factors are intended as practical starting points:
- Utilization factor: 0.80 — estimates how much emitted light reaches the useful room area.
- Maintenance factor: 0.85 — allows for dust, ageing and gradual reduction in output.
Lower factors produce a more conservative recommendation with a higher number of fittings.
How the calculation works
The calculator first multiplies the room area by the selected lux target.
It then compensates for expected utilization and maintenance losses.
The adjusted lumen requirement is divided by the lumen output of one fitting to estimate the quantity.
Ceiling height and beam angle
Ceiling height and beam angle help assess whether the selected fitting is appropriate, but they do not directly alter the lumen calculation in this version.
- Narrow beams are normally better for focused or accent lighting.
- Wide beams provide broader general coverage.
- Higher ceilings may require stronger fittings, narrower optics or a detailed photometric calculation.
What can affect the final result?
Actual lighting performance can vary according to:
- Ceiling and mounting height
- Beam angle and optical distribution
- Wall, ceiling and floor reflectance
- Dark furniture and interior finishes
- Fitting placement and spacing
- Glare control and visual comfort
- Task-specific lighting requirements
- The product’s photometric data
Use the result as a preliminary planning estimate rather than a complete photometric lighting design.
Lux & Lumens Calculator
Estimate the total light output and approximate number of fittings required for a rectangular room.
Advanced calculation options
How to Use the Lux & Lumens Calculator
Follow these steps to estimate the number of light fittings required for your room.
1 Select the room or activity
Choose the room or activity that most closely matches your space. The calculator will automatically apply a practical target lux level.
Select Custom lux target when you need to enter a specific project requirement.
2 Enter your room dimensions
Enter the room length and width in metres. The calculator multiplies them to determine the total floor area.
3 Enter the lumens per fitting
Use the lumen output shown in the product specifications. For example, enter 800 for a fitting rated at 800 lumens.
Do not enter wattage in this field. Wattage measures electrical consumption, while lumens measure the amount of visible light.
4 Review the estimated quantity
The result shows the adjusted lumen requirement and the estimated number of fittings. The fitting quantity is rounded up to the next complete number.
The grid spacing is an initial layout reference, not a guaranteed maximum spacing or final lighting plan.
Use the advanced factors
The default factors are intended as practical starting points:
- Utilization factor: 0.80 — estimates how much emitted light reaches the useful room area.
- Maintenance factor: 0.85 — allows for dust, ageing and gradual reduction in output.
Lower factors produce a more conservative recommendation with a higher number of fittings.
How the calculation works
The calculator first multiplies the room area by the selected lux target.
It then compensates for expected utilization and maintenance losses.
The adjusted lumen requirement is divided by the lumen output of one fitting to estimate the quantity.
Ceiling height and beam angle
Ceiling height and beam angle help assess whether the selected fitting is appropriate, but they do not directly alter the lumen calculation in this version.
- Narrow beams are normally better for focused or accent lighting.
- Wide beams provide broader general coverage.
- Higher ceilings may require stronger fittings, narrower optics or a detailed photometric calculation.
What can affect the final result?
Actual lighting performance can vary according to:
- Ceiling and mounting height
- Beam angle and optical distribution
- Wall, ceiling and floor reflectance
- Dark furniture and interior finishes
- Fitting placement and spacing
- Glare control and visual comfort
- Task-specific lighting requirements
- The product’s photometric data
Use the result as a preliminary planning estimate rather than a complete photometric lighting design.
What are lux and lumens?
Lumens measure the total amount of visible light produced by a lamp or fitting. Lux measures how much of that light reaches a surface. One lux equals one lumen distributed over one square metre.
The number of fittings needed depends on the room area, desired lux level, lumen output per fitting, light distribution, ceiling height, room finishes, and maintenance conditions.
How accurate is the calculator?
The Saleh Deco Lux & Lumens Calculator provides a preliminary planning estimate. It uses the room area, selected illuminance target, lumen output per fitting, utilization factor, and maintenance factor.
Actual results can vary according to beam angle, photometric distribution, mounting height, wall and ceiling reflectance, furniture, spacing, glare requirements, and the type of activity performed in the room.
Need help choosing a fitting?
Browse our lighting categories or contact Saleh Deco with your room dimensions, ceiling height, and intended use for a more detailed product recommendation.