High Bay & Warehouse Lighting Calculator
Work out how many LED high bays a space needs, how far apart to hang them, and what you save against metal halide or fluorescent. Built for warehouses, manufacturing plants, gyms and distribution centers with ceilings over 20 ft.
High bay lighting calculator
Enter the building length and width or total square feet, mounting height, space use (bulk storage, active warehouse, racked aisles, manufacturing or gym), the existing fixture (250 W, 400 W or 1000 W metal halide, 4 or 6-lamp T5HO, 8-lamp T8, or new build), operating schedule and electricity rate. Results show three columns kept separate: existing, LED only, and LED with optional occupancy sensors. Each shows fixture count, kW, kWh per year and cost per year, with the recommended LED lumens and watts, spacing, beam angle, savings and simple payback. Racked aisle mode lays fixtures along each aisle centerline. Results are estimates, not a photometric layout.
Typical LED replacements for high bay fixtures
Input watts include the ballast, which is what the meter sees. The LED wattage is the usual one-for-one replacement in an open area at a similar height.
| Existing fixture | Typical input watts | Typical LED replacement | Typical LED lumens |
|---|---|---|---|
| 250 W metal halide | about 290 W | 100 W | 13,000 to 15,000 |
| 400 W metal halide | about 458 W | 150 W | 20,000 to 22,000 |
| 1000 W metal halide | about 1,100 W | 300 to 400 W | 40,000 to 50,000 |
| 4-lamp T5HO | about 232 W | 100 to 120 W | 14,000 to 16,000 |
| 6-lamp T5HO | about 348 W | 150 to 165 W | 20,000 to 23,000 |
| 8-lamp T8 | about 224 W | 100 to 120 W | 14,000 to 16,000 |
Typical ranges. Confirm with the fixture spec sheet.
For 175 W and 320 W metal halide, HPS and 6-lamp T8 high bays, see the full metal halide to LED conversion chart.
How many high bay lights do I need?
Take a 100 × 200 ft warehouse (20,000 sq ft) with a 28 ft mounting height, active picking at a 30 fc target, running two shifts, with 50 existing 400 W metal halides.
- Height above the work plane: 28 − 2.5 = 25.5 ft. The room cavity ratio is 1.9, so the CU is about 0.75.
- LED package: 150 W at 21,000 lumens, the usual replacement for a 400 W metal halide.
- Fixtures for the light level: 30 × 20,000 ÷ (21,000 × 0.75 × 0.80) = 47.6, rounded up to 48.
- Layout: 5 rows of 10 = 50 fixtures at 20 ft × 20 ft, about 31 fc on average. The 2 extra fixtures keep the grid even.
- Energy: 50 metal halides at 458 W draw 22.9 kW. 50 LED high bays at 150 W draw 7.5 kW. At 4,680 hours a year that's 107,172 kWh down to 35,100 kWh, a saving of 72,072 kWh, or about $9,370 a year at $0.13/kWh.
- Payback: at $300 installed per fixture ($15,000 total), simple payback is about 1.6 years before any rebate.
A rough rule for 20 to 30 ft ceilings at 30 fc: one 150 W LED high bay for every 300 to 400 sq ft. At 15 fc for bulk storage, you need about half as many. Run your own dimensions in the calculator, because racking and ceiling height change the answer.
High bay spacing and mounting height guide
For even light in open areas, keep center-to-center spacing at about 1.0 to 1.5 times the mounting height, depending on the optic. Higher light levels pull fixtures closer, as in the example above. Keep the outer row about half a spacing from the walls. In racked aisles, hang one row down the center of each aisle.
| Mounting height | Typical beam angle | Typical LED package |
|---|---|---|
| Under 20 ft | 120° | Low bay or linear, up to 100 W |
| 20 to 30 ft | 90° | 100 to 150 W |
| 30 to 40 ft | 60° | 150 to 240 W |
| Over 40 ft | 60° | 240 to 400 W |
| Racked aisles, any height | 60° or aisle optic | Set by aisle length and light level |
High bay vs low bay lights
A high bay light is built for mounting heights of about 20 ft and up, with optics that push light down to the floor from that height. Low bay fixtures cover roughly 12 to 20 ft, with wider beams so the light spreads before it reaches the floor. They can look alike. The difference is the optic, the lumen package and the height they're designed for. For spaces under 20 ft, use the lighting layout calculator.
Rebates for warehouse LED upgrades
Most utilities pay incentives to replace metal halide and fluorescent high bays with LED, either as prescriptive rebates per fixture or as midstream (instant) discounts at the distributor. Many require DLC-listed fixtures, and adding occupancy or networked controls often earns more. Amounts change every program year, so check the current program before you quote.
When you need a real photometric layout
The calculator gives averages for open floors and simple aisles. Get a photometric layout from the manufacturer or a lighting designer when:
- Racking is tall. Racks block light, and the task is on the vertical rack faces, which an average on the floor doesn't capture.
- Something sits between the fixtures and the floor, such as mezzanines, conveyors or cranes.
- The task is safety-critical, with forklift traffic, moving machinery or busy loading docks.
- A code or spec sets minimums, such as emergency and egress lighting, or a client spec with uniformity ratios.
Ask for the IES files and run them in AGi32 or DIALux. Most manufacturers and their reps will run a layout for a real job at no charge.
From calculator to proposal
Quoting this job? LumaQuote builds the full audit, LED options, rebates and proposal per area.
Before you price it, a full lighting audit records the existing fixtures, hours and controls area by area, and the proposal has to show savings and payback the client can check. Here's how to build a lighting retrofit proposal that wins the job.
Start freeFree plan: 3 complete proposals, no credit card.
High bay lighting FAQ
How many high bay lights do I need for a 10,000 sq ft warehouse?
At a 25 ft mounting height with 150 W LED high bays (about 21,000 lumens), plan on about 16 fixtures for bulk storage at 15 fc, or about 30 for active picking at 30 fc. Racking, mezzanines and the exact layout change this, so run your own dimensions in the calculator.
What wattage LED replaces a 400W metal halide?
Usually a 150 W LED high bay with 20,000 to 22,000 lumens. A 400 W metal halide draws about 458 W with its ballast and loses a large share of its output as it ages, so a 150 W LED usually matches or beats the light the space actually has. In taller spaces, or where the client wants more light, step up to 200 W.
How far apart should high bay lights be?
In open areas, typically 20 to 30 ft apart at 25 to 30 ft mounting heights, and no more than about 1.0 to 1.5 times the mounting height. Higher light levels need tighter spacing. In racked aisles, run one row down the center of each aisle.
How many foot-candles does a warehouse need?
Typical targets are 10 to 20 fc for bulk storage, 20 to 35 fc for active warehousing and picking, and 30 to 50 fc for packing and light assembly. Loading docks are usually around 20 fc. These are design targets based on common IES guidance; your client's tasks may need more.
What's the difference between high bay and low bay lights?
High bay fixtures are designed for mounting heights of about 20 ft and up, with optics that push light down to the floor. Low bay fixtures cover roughly 12 to 20 ft with wider beams. The difference is the optic and lumen package, not the look.
Are occupancy sensors worth it in a warehouse?
Often, in aisles and storage areas that sit empty for much of the shift. LED high bays can switch or dim many times a day, unlike metal halide, and many energy codes now call for automatic shutoff or partial-off controls in warehouse storage areas on new work. Savings depend on traffic, so treat any percentage as a site-specific estimate. This calculator uses a conservative 20% default and shows the result as a range.