Convert Lux to Lumens – Light Calculator
This tool converts illuminance (measured in lux, lx) to total luminous flux (lumens, lm) for a specified area. Use it when you know the illuminance level across a surface and need the total emitted or required luminous flux for that surface.
Enter the illuminance in lux and the surface area in square metres. The calculation assumes uniform illuminance across the surface; if illuminance varies, use area-weighted averages or break the surface into zones and sum the results.
Governance
Record 7f3a21f46b0c • Reviewed by Fidamen Standards Committee
Inputs
Results
Total luminous flux
300
Lumens per square metre (sanity check)
300
| Output | Value | Unit |
|---|---|---|
| Total luminous flux | 300 | lm |
| Lumens per square metre (sanity check) | 300 | lm/m2 |
Visualization
Methodology
The underlying relationship is lumens = lux × area (in square metres). Lux is lumens per square metre, so multiplying by area yields total lumens incident on or required for that area.
Measurement and reporting guidance: use a calibrated illuminance meter whose spectral response approximates the photopic luminous efficiency function. For professional or regulatory work, ensure instruments are calibrated to a laboratory traceable to NIST or an ISO/IEC 17025-accredited calibration provider.
Key takeaways
This calculator gives a direct conversion from lux to lumens when a surface area is provided and assumes uniform illuminance.
For non-uniform lighting, divide the area into zones, compute lumens per zone, and sum. Verify instruments are calibrated and appropriate for the light spectrum encountered.
Worked examples
Example 1: 500 lux over 20 m² → lumens = 500 × 20 = 10,000 lm.
Example 2: 300 lux over 1.5 m² → lumens = 300 × 1.5 = 450 lm.
F.A.Q.
Do I need to provide area in square metres?
Yes. Lux is lumens per square metre, so converting to lumens requires the area in square metres. If you have area in other units, convert to m² before using this tool (1 ft² = 0.092903 m²).
Can I convert a lux reading from a handheld meter directly to lumens for a lamp?
Only approximately. A lux reading at a particular point or plane depends on distance, angle, and beam distribution. For a lamp's total lumen output, integrating sphere measurements or manufacturer-rated lumen output are appropriate. Use this tool for area-based estimations of incident luminous flux.
How accurate is the calculated value?
The numerical conversion is exact given the inputs, but real-world accuracy depends on sensor calibration, meter spectral response, angular response, spatial uniformity of illuminance, and rounding. For traceable accuracy use instruments calibrated to NIST or an ISO/IEC 17025-accredited lab and follow measurement standards.
Which standards apply to these measurements?
Relevant references include instrument calibration and measurement practice standards from NIST and ISO, workplace lighting guidance from OSHA and ISO, and consensus technical standards hosted by standards organizations. See citations for authoritative sources.
Sources & citations
- National Institute of Standards and Technology (NIST) — https://www.nist.gov
- ISO 8995-1 / EN 12464-1 (lighting of work places) - ISO catalogue — https://www.iso.org/standard/16861.html
- OSHA: Lighting - Occupational Safety and Health Administration — https://www.osha.gov/lighting
- IEEE Standards and technical resources — https://standards.ieee.org
- ISO 80000-7:2019 — Light and radiation — https://www.iso.org/standard/64978.html
- NIST SP 811 — Guide for the Use of the International System of Units — https://www.nist.gov/pml/special-publication-811
Further resources
Related tools
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
Record ID: 7f3a21f46b0cWhat changed (latest)
v1.0.0 • 2025-11-14 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Public QA status
PASS — golden 25 + edge 120
Last run: 2026-01-23 • Run: golden-edge-2026-01-23
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
What changed (latest)
v1.0.0 • 2025-11-14 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Public QA status
PASS — golden 25 + edge 120
Last run: 2026-01-23 • Run: golden-edge-2026-01-23
Engine
v1.0.0
Data
Baseline (no external datasets)
Content
v1.0.0
UI
v1.0.0
Governance
Last updated: Nov 14, 2025
Reviewed by: Fidamen Standards Committee (Review board)
Credentials: Internal QA
Risk level: low
Reviewer profile (entity)
Fidamen Standards Committee
Review board
Internal QA
Entity ID: https://fidamen.com/reviewers/fidamen-standards-committee#person
Semantic versioning
- MAJOR: Calculation outputs can change for the same inputs (formula, rounding policy, assumptions).
- MINOR: New features or fields that do not change existing outputs for the same inputs.
- PATCH: Bug fixes, copy edits, or accessibility changes that do not change intended outputs except for previously incorrect cases.
Review protocol
- Verify formulas and unit definitions against primary standards or datasets.
- Run golden-case regression suite and edge-case suite.
- Record reviewer sign-off with credentials and scope.
- Document assumptions, limitations, and jurisdiction applicability.
Assumptions & limitations
- Uses exact unit definitions from the Fidamen conversion library.
- Internal calculations use double precision; display rounding follows the unit's configured decimal places.
- Not a substitute for calibrated instruments in regulated contexts.
- Jurisdiction-specific rules may require official guidance.
Change log
v1.0.0 • 2025-11-14 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Areas: engine, content, ui • Reviewer: Fidamen Standards Committee • Entry ID: ad2a424039b6