Average illuminance (Eav) = total luminous flux of light source (n * Ф) * utilization coefficient (CU)* maintenance coefficient (MF)/ area (m2) (suitable for indoor or stadium lighting calculation).

Utilization coefficient: indoor 0.4, exercise 0.3.

Maintenance coefficient: generally 0.7 ~ 0.8.

For example, 1: Indoor lighting: 4× 5m room, using 9 sets of 3×36W grid lights.

Average illuminance = total luminous flux of light source ×CU×MF/ area

=(2500×3×9)×0.4×0.8÷4÷5

= 1080 lux

Conclusion: The average illumination is above 1000Lux.

Example 2: Gymnasium lighting: 20× 40m stadium, using 60 sets of powerspot 1000 w metal halide lamps.

Average illuminance = total luminous flux of light source ×CU×MF/ area

=( 105000×60)×0.3×0.8÷20÷40

= 1890 lux

Conclusion: The average horizontal illumination is above 1500Lux.

Design case of office average illuminance;

Design conditions: office length 18.2m, width 10.8m, ceiling height 2.8m, desktop height 0.85m, utilization coefficient 0.7, maintenance coefficient 0.8, and number of lamps and lanterns 33 sets. What is the average illumination in the office?

Lighting scheme: DiNiT 2X55W anti-glare fluorescent lamp is adopted, with luminous flux of 3000Lm and color temperature of 3000K, and the color rendering is above Ra90.

According to the formula:

Eav = (33 sets of x6000lm x 0.7x0.8) ÷ (18.2mx10.8)

=110880.00÷196.56 m2

= 564. 10Lux