Free Trailer Load Planner with Axle Weight Calculator

A loaded trailer works like a plank resting on two supports. The kingpin sits on the tractor's fifth wheel, which feeds weight to the drive tandem, and the trailer tandems carry the rear. Every pallet pushes down somewhere along that plank, and where it sits decides which support carries it: freight toward the nose loads the drives, freight toward the doors loads the trailer tandems, and freight in the middle splits between them.

That's why two loads with the same total weight can scale completely differently. 45,000 lb stacked in the nose can put the drives thousands of pounds over while the tandems ride light — slide the same freight back a few feet and both groups come in legal. The steer axle mostly carries the tractor itself, so loading changes move it the least.

On the Interstate system, federal law allows 20,000 lb on a single axle, 34,000 lb on a tandem and 80,000 lb gross. For a typical five-axle tractor-trailer that works out to the numbers every driver knows: about 12,000 lb on the steer (usually capped by the steer tires' rating rather than the law), 34,000 lb on the drive tandem and 34,000 lb on the trailer tandem — which is what this planner checks against by default.

States can differ off the Interstate, some run their own kingpin-to-tandem or bridge rules, and oversize/overweight permits change the math entirely. The limits here are the common working numbers, not a substitute for knowing the rules on your lane.

Kingpin-to-tandem (KPT) is the distance from the kingpin to the center of the trailer tandems. Sliding the tandems moves the trailer's rear support point under the load: slide them forward and they pick up weight the drives were carrying; slide them back and weight moves forward onto the drives. A commonly cited rule of thumb is roughly 250–400 lb shifted per hole depending on the slider's hole spacing — treat that as an estimate, not gospel.

KPT also matters on its own: several states limit it (California's ~40' rule being the famous one), so the legal slider positions can change with the state line. The planner's advanced settings let you set the tandem position and watch the axle weights move.

A reefer weighs more empty than a dry van — the insulated box, the refrigeration unit and its fuel commonly add a few thousand pounds, with typical 53' tares often quoted around 13,000–15,000 lb for a dry van and 15,000–17,000 lb for a reefer. Heavier tare means less legal payload before you hit 80,000 lb gross, which is why the same 44,000 lb load can be routine in a van and tight in a reefer. The planner accounts for trailer tare and the reefer unit's weight up front, and you can set your actual tare in the advanced settings.

The two calculate modes cover the two things dispatch actually asks for. Compact takes the least possible floor space — useful for partials and for leaving room for another pick. Balanced spreads the same freight along the trailer for the most axle headroom, which is the mode you want when the load is heavy and the scale is the worry. Both modes obey the same rule: no arrangement that breaks an axle limit.

You shouldn't have to retype a BOL into a load planner. Paste the pallet lines from your BOL, rate con or shipper email into the built-in BOL parser and it extracts counts, dimensions and weights for you — or upload the BOL itself as a PDF or photo. Digital PDFs are read directly; scans and photos go through OCR. Everything runs in your browser: your files and BOL text never leave your device.

Every parse lands in an editable preview first, with a flag on every assumption it made — total weights split per pallet, kilograms converted, assumed dimensions — so you confirm what actually goes on the trailer. If a messy BOL beats the standard parser, an optional Smart Parse button sends just what you're parsing — the text, or for a photo that photo — to a server for AI parsing; nothing is stored.