How to cube a 53 foot reefer

A step by step guide to fitting the most freight on a refrigerated trailer without going over weight or breaking the cold chain.

"Cubing" a trailer means working out how much freight will really fit, and in what order it should go on. On a refrigerated trailer, or reefer, there are four limits to watch: floor spots, cube, weight and temperature. Whichever one runs out first decides how full the truck can get. The numbers below are typical. Always check them against your own trailer specs.

Step 1: Count your floor spots

A common rule of thumb is that a 53 foot trailer holds 26 standard 48 by 40 inch pallets on the floor, single stacked. That is two pallets side by side, in 13 rows, with the 48 inch side running front to back. Thirteen rows of 48 inches is 52 feet, which is why it fits a 53 foot box with a little room to spare.

Your real number can be lower. Wide or overhung pallets, the space the reefer unit and its air chute need at the front, a bulkhead, or a pallet that will not sit flush can each cost a spot. Measure your own trailers once and write the number down.

Step 2: Know why a reefer holds less than a dry van

From the outside, a 53 foot reefer and a 53 foot dry van look the same size. Inside, the reefer is smaller. Its walls, roof, floor and doors are insulated, and that insulation takes up inches on every side. The cooling unit sits at the front, and air has to move around the load to keep it cold.

So don't plan a reefer with dry van numbers. Look up the inside length, width and height for your trailer model, or measure it.

Step 3: Cube, weight and pallet spots are three different limits

• Pallet spots are the places on the floor where a pallet can sit.
• Cube is the space inside the trailer: length times width times the height you can really use. On a reefer, the usable height is less than the ceiling, because air needs room over the top of the load.
• Weight is how many pounds the truck can carry and still be legal.

A trailer can run out of any one of these while the other two still have room. Light, bulky freight like chips or paper goods runs out of cube. Dense freight runs out of weight long before the floor is full.

Step 4: Check the weight first for produce and drinks

For many food loads, weight is the limit that bites first. A pallet of bottled drinks, canned goods, or dense produce like potatoes or melons is heavy. Fill all 26 spots with heavy pallets and the truck can be over weight well before it is out of space.

In general terms: the federal gross vehicle weight limit on the Interstate system is 80,000 pounds for the whole truck. That includes the tractor, the trailer, the reefer unit, the fuel and the driver. What is left is your payload, and it depends on how much your own tractor and trailer weigh. There are also limits for each group of axles, so where the weight sits matters too. States can have their own rules and permits, so check the rules for every state your trucks drive in, and use your own scale tickets to learn your real payload.

Step 5: Plan temperature zones and bulkheads

If you carry frozen, chilled and dry on one truck, you need a way to keep them apart. Multi-temp trailers use movable bulkheads, which are walls that split the trailer into sections. Each section is set to its own temperature.

• Decide how many floor rows each zone needs before you set the bulkheads.
• A bulkhead takes up space. Count that space when you count spots.
• Never block the air flow from the unit. Product jammed against the front wall or the ceiling can warm up or freeze.
• Check how your own trailers are built. Where the coldest zone sits affects which stops can go where.

Step 6: Load nose to tail in reverse stop order

The last stop loads first, at the nose. The first stop loads last, at the tail, next to the doors. That way the driver only ever unloads what is right in front of them. When zones and stop order fight each other, for example a frozen section at the front for a stop that comes early, the zone usually wins, and the driver needs to know which pallets to reach for.

Step 7: Build mixed pallets that travel well

• Heavy cases go on the bottom. Light and crushable cases go on top.
• Keep one stop's freight together and label every pallet with its stop.
• Keep the pallet inside its footprint. Overhang costs spots and breaks cases.
• Don't build mixed pallets so tall that they block air flow over the load.
• Brace the load with load bars or straps, so it does not shift as stops come off.

Where software helps

Doing this for every truck, every night, with late orders coming in, is where mistakes happen. Dock to Route checks floor positions, cube, weight and temperature zones together for each load, tells you which limit each truck hit first, and shows each trailer nose to tail with the last stop loading first. You set your own trailer sizes and limits, so the plan uses your numbers, not ours.