How many LED high bays do I need per m²?

How many LED high bays does a warehouse, workshop or sports hall need? That depends on three things: how much light has to reach the floor, how large the space is and how much light one fitting gives. In this article you will see how to work it out yourself, with a simple formula, a table of square metres per fitting and two worked examples from practice.

Step 1: how many lux does your space need?

The amount of light on the floor is expressed in lux. For a storage area where only goods are kept, 100 to 150 lux is enough. A warehouse where orders are picked needs about 200 lux. A workshop or production hall needs 300 lux, and for detailed work, inspection or assembly 500 lux is usual. A sports hall for recreation needs 300 lux and for competition 500 lux.

Step 2: the formula

The number of fittings you need is: lux times square metres, divided by the useful lumens per fitting. Not all the light from a fitting reaches the floor: part of it falls on walls and racking, and the light output decreases slightly over the years. That is why you calculate with about 60 percent of the lumens on the rating plate. A 150 watt high bay that gives 22,500 lumens therefore delivers about 13,500 useful lumens on the floor.

Table: square metres per high bay

Fitting	Useful lumens	200 lux	300 lux	500 lux
100 watts	approx. 9,000	45 m²	30 m²	18 m²
150 watts	approx. 13,500	67 m²	45 m²	27 m²
200 watts	approx. 18,000	90 m²	60 m²	36 m²
240 watts	approx. 21,600	108 m²	72 m²	43 m²

Divide the floor area of your hall by the figure in the table and round up. That tells you straight away how many fittings you need.

Worked example 1: workshop of 1,000 m², 8 metres high

A workshop of 25 by 40 metres needs 300 lux. At 8 metres a 200 watt high bay is a good fit. According to the table, one 200 watt fitting lights about 60 m² at 300 lux. 1,000 divided by 60 is 16.7, so rounded up 17 fittings. In practice you choose a regular pattern, for example 3 rows of 6, so 18 high bays. The spacing is then about 7 to 8 metres, which suits a mounting height of 8 metres well.

Worked example 2: storage hall of 600 m², 7 metres high

A storage hall of 20 by 30 metres needs 150 lux. With 150 watt high bays you get 600 times 150 divided by 13,500, so about 7 fittings. In a regular pattern that becomes 2 rows of 4, so 8 fittings. But check the spacing: the rows are then 10 metres apart, which is at the limit for a height of 7 metres. It gets darker between the rows. Better is 3 rows of 4, so 12 lighter 100 watt high bays. That is the same total power of 1,200 watts, but the light is much more even and you reach about 180 lux.

Always check the spacing as well

The number of fittings from the formula is a minimum. Afterwards, always check that the distance between the lights is not more than one and a half times the mounting height. If it is, choose more fittings with a lower wattage. With high racking and narrow aisles, hang the fittings above the aisles and choose a narrow 60 degree lens.

Advice for your hall

Send the dimensions, height and use of your hall to info@dimay.com and we will work out the number of fittings and the best layout for you. Also see our LED high bay lighting and the linear high bays, and read how high to mount a high bay and how many lumens you need.

Frequently asked questions about the number of high bays