Calculators and photometric tools
Free lighting design tools
Eleven free lighting tools built by a practising lighting designer for lighting designers, electrical engineers and specifiers: an IES and LDT photometric viewer, converter and validator, and calculators for the lumen method, maintenance factor, LENI, daylight factor, lighting controls savings, LED payback, TM66 circularity, central battery sizing, bathroom IP zones and BUG ratings. No account is needed; Pro adds batch processing and PDF reports.
By Nicholas RedicanLast reviewed
Photometric file tools
The IES/LDT editor opens IESNA LM-63 and EULUMDAT files, plots the polar intensity distribution, calculates beam angles at 50 and 10 per cent of peak, verifies the total lumen output by zonal integration and reports the CIE flux code. The same component is presented as three tools because they are three different jobs: viewing a file, converting between IES and LDT, and validating a file before it goes into a Dialux or AGi32 model.
- IES and LDT viewer: header data, rated and calculated lumens, watts and efficacy free; polar curves, beam angles and CIE classification with Pro
- LDT to IES converter (and IES to LDT): single-file and batch conversion, a Pro feature
- IES file validator: structural errors, angle mismatches, missing TILT lines and lumen discrepancies checked free on every upload; repair with Pro
Lighting calculations
- Lumen method calculator: luminaire count for a target lux from room index, utilisation factor and maintenance factor, to BS EN 12464-1
- Maintenance factor calculator: LLMF × LSF × LMF × RSMF with LED lifetime and environment presets
- Daylight factor calculator: average daylight factor by the BRE method
Energy and compliance
- LENI calculator: Lighting Energy Numeric Indicator to BS EN 15193 for Part L
- Lighting controls savings calculator: occupancy, daylight dimming and scheduling savings with payback
- LED lighting ROI and payback calculator for upgrades and retrofits
Emergency, safety and exterior
- Central battery calculator: emergency lighting battery sizing to BS EN 50171 for 1 or 3 hour duration
- Bathroom lighting zones and IP rating checker to BS 7671 Section 701
- BUG rating and dark-sky compliance checker per IES TM-15, with notes on UK ILP environmental zones
- TM66 circularity pre-assessment for luminaires (indicative, not the licensed CIBSE CEAM tool)
Which standards do the calculators follow?
Each tool page names the standard or method it implements: BS EN 12464-1 and the SLL Code for illuminance, CIE 97 and the SLL Code for maintenance factors, BS EN 15193-1 for LENI, the BRE average daylight factor formula, BS EN 50171 and BS 5266-1 for central battery systems, BS 7671 Section 701 for bathroom zones, IES TM-15 for BUG ratings and CIBSE TM66 for circularity. The results are indicative design values: a lighting designer should sign off anything submitted for planning, building control or BREEAM.
Free and Pro
Every calculator, the IES/LDT viewer and the validator are free to use without an account. A Pro subscription unlocks IES/LDT conversion (single file and batch), the advanced photometric analysis (beam angles, polar diagram, CIE classification, lumen verification), sanitise and repair, and PDF report exports across the calculators.
Frequently asked questions
Are the lighting tools free?
Yes, with one exception. The ten calculators, the IES/LDT viewer and the validator can be used free of charge without creating an account. IES/LDT format conversion is a Pro feature, and Pro also adds the advanced photometric analysis, file repair, batch processing and PDF report exports.
Are my photometric files uploaded anywhere?
The IES and LDT files you open, and the figures you type into the calculators, are sent to NR Lighting’s own cloud functions for parsing and calculation and are not published or shared. See each tool page for the detail of how it processes your data.
What does Pro add?
In the IES/LDT editor: conversion between IES and LDT (single file and batch), beam angle detection at 50 and 10 per cent of peak, an interactive polar diagram, CIE classification, total lumen verification from the candela data, sanitise and repair of faulty files, and PDF reports. In the calculators: PDF report exports and multi-zone or comparison features where the tool supports them.
Which standards do the calculators follow?
BS EN 12464-1 and the SLL Code for illuminance and the lumen method, CIE 97 for maintenance factors, BS EN 15193-1 for LENI, the BRE formula for daylight factor, BS EN 50171 and BS 5266-1 for central battery sizing, BS 7671 Section 701 for bathroom zones, IES TM-15 for BUG ratings and CIBSE TM66 for circularity. Each tool page names its method.
Can I use the results in a Part L or planning submission?
The tools give indicative design values suitable for early-stage checks and comparisons. Submissions for planning, building control or BREEAM should be prepared and signed off by a lighting designer with the full calculation model, which NR Lighting provides as a service.