Number of fixtures required N = (E·A) / (Φ·UF·MF) The luminaires are determined by: target illuminance (E), area (A), luminaire luminescent flux (Φ), utilization factor (UF), and maintenance factor (MF). For example, for 500 lux, 100 m², a 4000 lm luminaire, UF 0.5, and MF 0.8, approximately 32 luminaires are required.

N = (E · A) / (Φ · UF · MF)
Example calculation: 500 lux target, 100 m² office, 4000 lm luminaire, UF 0.5, MF 0.8 → N = (500×100)/(4000×0.5×0.8) = 31.25 → 32 luminaires.

Number of Luminaires (Lumen Method)

Calculate the target illumination level and the number of luminaires required for the area using the lumen method.

Necessary fixtures
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The actual average
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Notes: N = (E·A) / (Φ·UF·MF). Usage factor (UF) space geometry, reflection and luminaire type; maintenance factor (MF) It depends on contamination/aging — precise values are taken from luminaire efficiency tables. The result is for average illumination; uniformity (Uo) is evaluated separately.
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How is it calculated?

  1. Enter the target illumination (lux) and area (m²).
  2. Enter the luminaire's luminous flux (lumens).
  3. Press Calculate with the Usage (UF) and Maintenance (MF) factors.

Frequently Asked Questions

What is the lumen method?
This method calculates the total luminous flux and number of luminaires required to achieve an average illumination level in a space.
What is the factor of use (UF)?
It is the ratio of light emitted from the luminaire to the light reaching the working plane; it depends on the room geometry, reflection coefficients, and luminaire type (taken from the luminaire catalog).
Why is the maintenance factor (MF) necessary?
Over time, contamination and lamp aging reduce brightness; MF (typically 0.7–0.8) compensates for this loss from the start.

Related tools and services

This tool and its content are for general informational purposes only; they do not constitute a binding inspection/declaration of conformity. Definitive results will be determined through on-site inspection in accordance with relevant legislation and standards. Get a quote →