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Lighting Design

Lighting Calculator: Lux, Lumens and Fixtures

Calculate required lumens, LED fixture quantity, achieved illuminance, connected watts, current, and preliminary lighting-circuit count.

Lighting calculation equations

The lumen method estimates average maintained illuminance from room area, fixture output, utilization, and maintenance conditions.

Φrequired = E × A / (UF × MF)
N = ceil(Φrequired / Φfixture)
Einstalled = N × Φfixture × UF × MF / A
I = N × Pfixture / (V × pf)

where:

Φrequired
Fixture lumens required before utilization and maintenance losses[lm]
E
Target or achieved maintained illuminance[lx]
A
Illuminated area[m²]
UF
Utilization factor
MF
Maintenance factor
N
Whole number of fixtures
Φfixture
Rated luminous flux per fixture[lm]
Pfixture
Input power per fixture[W]
I
Steady-state lighting current[A]

A lumen-method result does not prove uniformity, glare control, emergency-lighting compliance, or LED-driver inrush compatibility.

How to use the Lighting Calculator: Lux, Lumens and Fixtures

Choose the space or task to load a broad starting illuminance value, or enter custom lux from the applicable project requirement. Add the room dimensions, utilization and maintenance factors, and the exact fixture lumen and watt ratings. The result connects the lighting requirement to fixture quantity and electrical circuit load.

  1. Choose a space preset or custom maintained illuminance.
  2. Enter room dimensions or illuminated area.
  3. Enter utilization and maintenance factors from project data.
  4. Enter rated lumens, watts, voltage, and power factor for one fixture.
  5. Review fixture quantity, achieved lux, connected load, current, and preliminary circuit count.

Calculation method and validation

The equations and symbol definitions above show the complete calculation basis. Inputs are checked before calculation so zero, negative, incompatible, or physically impossible combinations are flagged instead of silently producing a misleading result.

How to interpret the result

Use the main result as a starting value and read every supporting metric. Average maintained illuminance over the entered area Uniform fixture distribution and representative utilization factor Balanced fixture loading where more than one circuit or phase is used A passing or recommended result means the entered mathematical conditions are satisfied; it does not certify the complete installation or a particular product combination.

  • Average maintained illuminance over the entered area
  • Uniform fixture distribution and representative utilization factor
  • Balanced fixture loading where more than one circuit or phase is used

Selection limits and next checks

Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions. The preset lux values are broad planning references, not a substitute for the applicable workplace, emergency-lighting, local energy, or project standard. LED-driver inrush current and maximum devices per MCB may govern circuit count even when steady-state current is low. Compare the output with the current applicable standard, local rules, exact VIOX product datasheet, environmental conditions, protection coordination, and the engineer's project requirements before procurement or installation.

Continue with energy cost calculatorContinue with maximum demand calculatorContinue with mcb inrush compatibility checker

Assumptions

  • Average maintained illuminance over the entered area
  • Uniform fixture distribution and representative utilization factor
  • Balanced fixture loading where more than one circuit or phase is used

Important Warnings

  • Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions.
  • The preset lux values are broad planning references, not a substitute for the applicable workplace, emergency-lighting, local energy, or project standard.
  • LED-driver inrush current and maximum devices per MCB may govern circuit count even when steady-state current is low.

FAQ

How many lumens do I need for a room?

Multiply target lux by area, then divide by utilization and maintenance factors. A direct lux × area calculation assumes every emitted lumen reaches a perfectly maintained working plane.

What is the difference between lux and lumens?

Lumens measure luminous flux emitted by a source. Lux measures illuminance received on a surface; one lux equals one lumen per square metre.

Why does this calculator use utilization and maintenance factors?

Fixture optics, room geometry, surface reflectance, dirt, and lumen depreciation mean only part of rated fixture lumens contributes to maintained illuminance on the working plane.

Can the result select an MCB for LED lighting?

Not by steady-state watts alone. Check cable capacity, permitted voltage drop, driver inrush magnitude and duration, breaker curve, maximum drivers per device, switching duty, and manufacturer data.

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