How Many LED High Bay Lights Do I Need? A Warehouse Lighting Layout Guide

Ask three suppliers how many high bays your warehouse needs and you may get three different answers. Usually the difference is not the luminaire. It is the light level they assumed, the beam angle, or whether anyone checked the spacing. This guide shows how to work it out yourself in about ten minutes, so you can check any proposal you receive.

You can also skip the arithmetic and use our free high bay lighting calculator, which follows exactly the method below and draws the layout.

Step 1: decide the light level

Start from what people do in the space, not from the old installation. The European standard for indoor workplaces, EN 12464-1, gives maintained average illuminance values that most designers worldwide use as a reference:

“Maintained” means the level after the luminaires have aged and collected dust, which is why the calculation includes a maintenance factor.

Step 2: find the height that matters

What counts is the mounting height above the working plane (Hm): the height of the luminaire minus the height where the work happens, usually 0.8 m for benches or 0 m for floor-level storage. A high bay mounted at 10 m above a workbench has Hm = 9.2 m.

Step 3: estimate the utilisation factor

Not all the light from a luminaire reaches the floor. Some hits the walls and some is absorbed. The utilisation factor (UF) is the fraction that arrives on the working plane. It depends on the shape of the room, described by the room index:

K = (L × W) ÷ (Hm × (L + W))

Long, wide, low halls have a high K and a high UF. Narrow, tall rooms have a low K and lose more light on the walls. For LED high bays with faceted aluminium reflectors, typical values are:

Light-coloured walls and ceilings add a few points; dark steelwork removes several. The exact figure comes from the luminaire photometric file.

Step 4: count the luminaires

N = E × A ÷ (Φ × UF × MF)

• E: target illuminance (lx)
• A: floor area (m²)
• Φ: lumens per luminaire (watts × lm/W)
• MF: maintenance factor, typically 0.8 for LED in a clean hall and 0.7 in dusty plants

Step 5: check the spacing

This is the step most quick quotes skip. If the high bays are too far apart, the floor gets bright pools under each fixture and dim bands in between. Keep the spacing below:

If the spacing check forces more fixtures than the light level needs, use more fixtures of a lower wattage rather than fewer, brighter ones.

Worked example: a 60 × 30 m warehouse

A warehouse of 60 × 30 m with high bays at 10 m, order picking at bench height (0.8 m), target 200 lx, using 150 W high bays at 130 lm/W with 90° reflectors:

1. Hm = 10 − 0.8 = 9.2 m
2. K = (60 × 30) ÷ (9.2 × 90) ≈ 2.2, so UF ≈ 0.67
3. Φ = 150 × 130 = 19,500 lm
4. N = 200 × 1,800 ÷ (19,500 × 0.67 × 0.8) ≈ 34.4, so 35 luminaires
5. Spacing limit = 1.2 × 9.2 ≈ 11 m. Arranged to the hall’s proportions, 8 rows × 5 columns = 40 fixtures at 7.5 × 6 m, well inside the limit.

Result: 40 × 150 W, about 230 lx average and 3.3 W/m². A 5 × 5 grid of 250 W fixtures would reach a similar average with fewer fittings, but its 12 m spacing along the hall exceeds the 11 m limit, so the floor would be patchy.

Our high bay lighting calculator runs all five steps at once and checks the spacing for you:

Open this example, then try 250 W fixtures: the calculator keeps within the spacing limit by choosing a 6 × 4 grid instead of 5 × 5.

High bay light layout: rules of thumb

Once the count is known, the layout decides whether the hall looks evenly lit. Rules that apply to almost every hall:

Uniformity. The ratio of minimum to average illuminance (Uo) should usually be at least 0.4 for storage and rough work and 0.6 for work areas, following EN 12464-1. The spacing rules above get close; a photometric calculation with the luminaire file confirms it.

Emergency lighting. Plan escape-route and open-area emergency lights in the same layout, either as separate fittings or as high bays with emergency battery packs.

Racking aisles are a different job

High racking turns a hall into a set of narrow corridors. Light from a wide-beam fixture hits the top of the racks and never reaches the aisle floor. For racks above about 6 m:

• put one line of luminaires along the centre of each aisle,
• use narrow beams (60° or an aisle-specific optic),
• calculate each aisle as its own long, narrow room, and check the vertical light on the rack faces where labels are read.

Hot, dusty and wet halls

The method stays the same, but the luminaire choice changes:

• Steel plants, foundries, glass works: the air under the roof can exceed 50 °C. Use heat-pipe high bays or models rated for high ambient temperatures, such as our high-temperature high bay rated to 65 °C.
• Food plants and washdown areas: IP65 or better, with sealed glass rather than open reflectors.
• Cement, mining and grain: use a lower maintenance factor (0.7) and plan for cleaning.

Checklist before you order

• Target lux per area, not one number for the whole building
• Mounting height and working-plane height
• Beam angle chosen for the height and for any racking
• Spacing within the limit for that beam
• Lumens measured for the complete luminaire (not LED chip lumens)
• Photometric (IES/LDT) file available, so the design can be verified

If you send us a floor plan with the mounting heights, we will return a layout and a lighting simulation. Our LED high bay range runs from 30 W to 1500 W in heat-pipe, fin and UFO designs.