How Much Warehouse Space Do I Need?

When companies look for warehouse space, the first number they reach for is usually a total square footage based on a current building or a guess. That number hides the decisions that actually drive the size: how many pallets, how high they stack, what type of forklift you run, and how much floor goes to work other than storage. Two companies with the same inventory can need very different buildings.

So build the number from the bottom up. It takes a few hours with your inventory data and it makes every later conversation sharper. Use the result as a planning estimate, then have a rack supplier or layout designer test it on an actual floor plan.

1. Count peak inventory in pallets. Use your busiest period and not your annual average, and add anything stored on the floor or in shelving.
2. Measure your pallets and how tall and heavy loaded pallets are. A typical US pallet is 42 by 48 inches, according to a STRUCTURE magazine article on rack design, and that article lists common pallet heights of 56, 64 and 72 inches. Your product may differ.
3. Choose a target height. Rack levels depend on clear height and pallet height, and each level needs the pallet height plus clearance. The same article uses an 8-inch allowance. Leave room below the sprinklers too.
4. Convert pallets to rack bays. Divide pallet positions by pallets per bay per level, then by levels.
5. Set the aisle width from your forklift, using the manufacturer's specification and not a habit.
6. Calculate rack and aisle area, using the depth of a back-to-back row and half of the aisle on each side.
7. Add the other work areas: receiving and shipping staging, packing, production, returns, charging, office and restrooms.
8. Add growth, based on your business plan, and decide how much empty space you can afford to carry in the early years of the lease.

Aisle width is the most common hidden driver, and it is set by your truck. Toyota's guide to the topic defines aisle width as the minimum width of a straight aisle in which a truck carrying a given load can turn 90 degrees, based on the turning radius, the load dimensions and a safety clearance. Cisco-Eagle, a material handling supplier, notes that many warehouses are simply set to 12 feet whether or not that is the right width. It also says a conventional counterbalanced forklift needs about 12 feet for picking and placing pallets, and that narrow aisle vehicles need less.

Narrower aisles fit more storage into the same floor, but the equipment costs more and the safety margin needs thought. OSHA requires sufficient safe clearances for aisles, at loading docks, through doorways and wherever turns are made when mechanical handling equipment is used, and requires permanent aisles to be marked. OSHA's text does not give a single width that fits every operation, so use the forklift specification and have your supplier and safety advisor confirm the layout.

Get the forklift decision made before you tour. A building can look too small with one truck and comfortably large with another.

This example is hypothetical, for illustration. None of its numbers are market data, and the storage layout would need a designer's review.

Imagine a distributor that needs 1,200 pallet positions at peak, with 64-inch-tall loaded pallets. It assumes 2 pallets per bay on each level and 4 levels, so each bay holds 8 pallets. That is 150 bays.

• Bay footprint: racks at 4 feet deep and 8 feet long, in back-to-back rows with a 6-inch spacer, use a row depth of 8.5 feet.
• Aisle: assuming a 12-foot aisle, one row pair plus one aisle takes up 20.5 feet of width, or 10.25 feet per side.
• Area per bay: 8 feet by 10.25 feet is 82 square feet.
• Rack and aisle area: 150 bays at 82 square feet is 12,300 square feet.
• Other areas, all assumed: cross aisles and perimeter 2,000, dock staging 2,000, packing 1,500, office and restrooms 1,000. That adds 6,500 square feet, for 18,800 in total.
• Growth, assumed at 15 percent: 18,800 times 1.15 is 21,620 square feet.

Now check height. A level for a 64-inch pallet plus an 8-inch allowance is 72 inches, or 6 feet, so 4 levels reach 24 feet at the top of the load. Add 18 inches to the sprinkler level, which is the general minimum clearance in OSHA's sprinkler rule, and this layout needs more than 25.5 feet of clear height at the rack locations. In a building with less height, 3 levels would raise the bay count to 200 and the rack and aisle area to 16,400 square feet. That single change adds 4,100 square feet before growth.

OSHA's letter on the rule notes that some sprinkler designs for high rack storage require more than 18 inches, so your fire protection engineer, insurer and fire official have the final word.

Storage calculations are the easy part. Operators more often run short in the areas around it.

• ✓Where do inbound pallets sit while they are checked and put away?
• ✓Where do outbound orders stage before the truck arrives, and how many trucks can be at the door at once?
• ✓Where do packing, kitting, repair and returns happen?
• ✓If forklifts are electric, is there a designated charging area? OSHA requires one, with provisions for ventilation, fire protection and spills.
• ✓Is there room for empty pallets, trash and recycling, and spare parts?
• ✓How many desks, restrooms and parking spots do the people on the busiest shift need?
• ✓Do any products need separate storage because of fire, food or security rules?

Once you have a range, turn it into a building specification: floor area, minimum clear height at the racks, door count by type, and power. That lets you compare a smaller, taller building against a larger, lower one on the same terms, since you may hold the same inventory in less floor area with more height.

Then test your growth assumption against the lease. Taking space early means paying for it while it sits empty, while too little may lead to a costly second move. Expansion rights, subleasing rights and term length can reduce that risk, and these belong in the negotiation.

Tenant Advisory Group represents tenants and buyers. In an industrial search, we help turn your inventory and growth figures into a requirement, then bring in the rack designers and engineers needed to test specific buildings before you commit.