TowingMath

Trailer Cargo Capacity Calculator

What your trailer can actually carry once water, propane and batteries have taken their share.

Your numbers

From the VIN plate near the coupler.
Dry weight or UVW. A scale reading is far better than a brochure figure.
8.34 lb per gallon.
Anything fitted after the dry weight was measured.
Cargo capacity left —

Enter your numbers above.

Verify before you tow. These figures are a planning aid, not professional or engineering advice. Your real limits are the ones printed on your vehicle's door-jamb placard, your trailer's VIN plate, and your owner's manual - and those override anything calculated here. When numbers are close, weigh the rig and go with the more conservative answer.

The formula

Gross cargo capacity = GVWR - empty weight

Then subtract everything that is not "cargo" but still rides along:

Usable cargo = Gross cargo capacity
             - fresh water (gallons x 8.34 lb)
             - propane
             - batteries and added options

Worked example

GVWR                              7,600 lb
Empty weight (UVW)               -5,800 lb
                                 ---------
Gross cargo capacity              1,800 lb

Fresh water, 40 gal x 8.34         -334 lb
Propane, two cylinders              -40 lb
Two batteries + awning             -130 lb
                                 ---------
Usable cargo capacity             1,296 lb

The sticker said 1,800 lb. Before a single item is packed, 504 lb of it is already spoken for. That gap is where most overloaded trailers come from - the number people plan against is the one on the brochure, not the one that is left.

Common questions

How do I calculate a trailer's cargo capacity?

Subtract the trailer's empty weight from its GVWR. On an RV this is stated directly as CCC (cargo carrying capacity) or NCC (net carrying capacity) on a yellow sticker inside the trailer.

Watch which empty weight you are using. Dry weight or UVW is the trailer as it left the factory, and it usually excludes fresh water, propane, batteries and every dealer-installed option. Weighing the trailer as it sits gives you a real number instead of an optimistic one.

Does fresh water count against cargo capacity?

Yes, unless the manufacturer's sticker explicitly says the full fresh tank is already accounted for. Water is 8.34 lb per gallon, so a 40-gallon tank is over 330 lb of your cargo allowance.

Waste tanks count too, and they fill up as the trip goes on. A trailer weighed on the way out is lighter than the same trailer on the way home.

What is the difference between dry weight and GVWR?

Dry weight, sometimes UVW, is what the trailer weighs empty. GVWR is the maximum it may weigh loaded. The gap between them is everything you are allowed to add.

Dry weight figures in brochures are frequently for a base model without options. An awning, a second air conditioner, solar panels and a generator can eat several hundred pounds of that gap before you load a single item.

Does cargo capacity include tongue weight?

Cargo capacity is about the trailer's own GVWR, and the loaded trailer weight that GVWR governs includes everything aboard.

Tongue weight is a separate question: it is the portion of that loaded weight carried by the tow vehicle, and it counts against the tow vehicle's payload. Both limits apply at the same time, to two different vehicles.

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