How to do lighting calculations
Lighting calculations turn a project lighting brief, room geometry and verified photometric data into evidence for maintained illuminance, uniformity, glare, energy and the coordinated luminaire layout.
Lighting calculations turn a project lighting brief, room geometry and verified photometric data into evidence for maintained illuminance, uniformity, glare, energy and the coordinated luminaire layout.
What this report needs to prove.
The page targets “how to do lighting calculations” while keeping the report-template query on its own page.
Start with the visual task
Choose the maintained illuminance, uniformity, glare, colour and control requirements for the actual use, not a generic room label.
Use verified photometry
Luminaire lumens alone are not enough for a detailed layout. Use current photometric files, distribution data, mounting information and manufacturer maintenance data.
Check more than average lux
Review the calculation grid, minimum values, uniformity, glare, vertical illuminance, daylight and controls where the project requires them.
How to prepare the assessment and report.
Use controlled source information, keep each modelling decision traceable and obtain competent-person review before issue.
Set the lighting criteria
Record the space use, visual tasks, maintained illuminance, uniformity, glare, colour, emergency and control requirements.
Build the room and reflectance model
Enter the real dimensions, calculation plane, obstructions, surface reflectances and daylight openings needed for the chosen method.
Select verified luminaire data
Use the proposed luminaire photometry, luminous flux, power, mounting height, orientation and maintenance information.
Calculate and coordinate the layout
Run the model, inspect the grid and contour results, adjust spacing and coordinate the layout with ceilings, structure and building services.
Check quality and energy
Review average and minimum illuminance, uniformity, glare, controls, installed load and the applicable energy method.
Issue the calculation report
Record the input revisions, software, calculation surfaces, luminaire schedule, results, exceptions and reviewer comments.
Information to gather before you start.
Missing inputs should remain visible as review items. They should not be replaced with convenient assumptions without approval.
| Input group | Source information | Why it matters |
|---|---|---|
| Design criteria | Maintained lux, uniformity, glare, colour, controls and task requirements | Defines the target |
| Room geometry | Dimensions, workplane, ceiling, obstructions and surface reflectances | Defines the calculation space |
| Luminaire data | IES or LDT photometry, lumens, wattage, distribution, mounting and tilt | Defines light output and distribution |
| Maintenance factors | Lamp lumen, survival, luminaire and room-surface factors as applicable | Converts initial to maintained performance |
| Layout and controls | Quantity, coordinates, spacing, circuits, occupancy and daylight controls | Defines the proposed scheme |
| Results | Average, minimum, uniformity, glare, energy and calculation images | Supports design review |
What the issued report should contain.
Use the separate template page when the search task is to find the report layout rather than understand the assessment.
| Section | Required coverage |
|---|---|
| Executive summary | Space coverage, design criteria, headline results, exceptions and actions. |
| Design basis | Project stage, standards, room uses, target values, controls and exclusions. |
| Calculation model | Software, room geometry, reflectances, workplanes, grids and daylight assumptions. |
| Luminaire and maintenance data | Luminaire schedule, photometric files, output, power, mounting and maintenance factors. |
| Results | Average and minimum illuminance, uniformity, glare, energy, contours and calculation images. |
| Coordination and review | Layout issues, emergency-lighting boundary, controls, assumptions, deviations and sign-off. |
Standards and guidance to check.
The project team must confirm the current edition, jurisdiction, contractual requirements and authorised access to each publication.
- SLL Code for Lighting (2022)The current SLL Code covers lighting criteria, indoor calculations, photometric data, maintenance and verification.
- SLL Lighting Handbook (2018)The handbook follows the lighting design process from early decisions through detailed design, commissioning and handover.
- Approved Document LFor projects in England, confirm the current lighting energy requirements and applicable calculation route.
Prepare the report in Adelphos Chat.
Collect the inputs, identify missing evidence and build the report structure now. Report Studio templates are being prepared for release.
How to do lighting calculations questions
What is the basic lighting calculation formula?
A simple lumen-method estimate relates maintained illuminance to luminaire quantity, luminaire flux, utilisation and maintenance factors over the room area. Detailed design should use verified photometry and an appropriate calculation model.
What information is needed for a lighting calculation?
You need the design criteria, room geometry, surface reflectances, calculation plane, luminaire photometry, lumen output, wattage, mounting, maintenance factors, layout and control strategy.
Is average lux enough to approve a lighting design?
No. Depending on the brief, the designer may also need to check minimum illuminance, uniformity, glare, vertical or cylindrical illuminance, colour, controls, energy and emergency lighting.
Can I use the free Adelphos lux calculator?
Yes. The free calculator is useful for an early lumen-method estimate. Use a detailed photometric calculation and competent review for the final coordinated lighting design.
Continue with the evidence.
Move between the technical guide, the report structure and the calculation tools without mixing their search intent.
Adelphos structures declared evidence and report content. A competent person remains responsible for the model, calculations, standards, assumptions, interpretation, coordination and issued conclusion.