Max payload calculator

How the calculator works

Payload is the room left for cargo under the lowest gross limit that applies to you. The calculator compares up to three limits and uses the lowest:

• The manufacturer rating. GVWR for a single truck such as a 26 ft box truck, GCWR for a truck and trailer together. You can never legally run above it.
• The federal Interstate limit. 80,000 lb gross on the Interstate System, unless the bridge formula sets a lower figure for your axle spacing.
• Any other limit you enter. A state or route limit, a posted bridge, or the weight on a permit.

Source:23 CFR 658.17, Interstate weight limits: 80,000 lb gross, 20,000 single, 34,000 tandem, Bridge Formula, grandfather rights, permits (2025 edition) · checked 2026-10

From that limit it subtracts the tare: everything on the scale that isn't cargo. That means the truck or tractor, the trailer, the fuel on board and the driver with their gear. The bar under the result shows how the gross limit splits between tare and payload.

Worked example

Example

Gross limit

80,000 lb

Tractor + trailer

33,500 lb

Fuel, driver, gear

1,700 lb

Payload remaining

44,800 lb

Governing limit

Federal 80,000 lb

Tare share

42%

Switch the preset to a flatbed and the payload climbs, because the trailer weighs less. Switch to a hotshot and the manufacturer rating governs instead of the federal limit. Every preset is an example; replace it with your own scale tickets.

Getting accurate tare weights

The easiest way is to weigh the truck and trailer empty, fueled the way you usually run, with your gear on board. A certified truck scale gives you the total and often the split by axle group. Keep the ticket; it's the number every payload decision starts from.

Watch the things that creep in. A second fuel tank, a heavier headache rack, an extra set of chains or a stack of tarps all eat into payload. On a flatbed, tarps alone can weigh hundreds of pounds. On a box truck, a liftgate takes weight you can't load.

Payload by rig type

Each kind of truck hits a different limit first, which is why the calculator lets you pick the governing limit rather than assuming 80,000 lb.

• Tractor-trailers usually run into the federal 80,000 lb gross limit or an axle limit before their manufacturer rating. Trailer choice matters: aluminum and lighter designs leave more room for cargo than heavier steel builds.
• Hotshots are limited by the manufacturer's combination rating long before 80,000 lb. A heavier trailer or a bigger truck changes the rating and can change the license class you need, so check both before you buy.
• 26 ft box trucks are limited by GVWR, and the box, the liftgate and any shelving all come out of payload. A box truck rated 26,000 lb or less needs no CDL, and that same rating caps what it can ever legally carry.
• Reefers carry the refrigeration unit and its fuel on the trailer, so a reefer trailer usually leaves less payload than a dry van of the same length.

Whatever you run, weigh it once properly and write the tare down where your dispatcher can see it.

What good and bad results mean

A healthy payload matches the freight you want to haul. If you run heavy commodities like steel, lumber or machinery, every pound of tare is a pound of cargo you can't sell, and a lighter trailer can pay for itself. If you run light, bulky freight, payload rarely limits you and space matters more.

A payload close to zero means the setup can't legally carry much at all. Check the rating first: some combinations are rated lower than people assume. Then check the tare.

Gross is only the first check. The cargo also has to sit so no axle goes over its limit; plan that with the federal bridge formula calculator. Spring weight restrictions on some roads can lower the legal gross further; see frost laws by state. Tires have load ratings too; our guide to tractor-trailer tire pressure covers the basics. And weight violations show up in your safety record; see the CSA score estimator.