RV and Trailer Calculators
Trailer payload.
Enter the GVWR and the unloaded weight, add water, propane, gear and aftermarket extras, and see the cargo capacity that is left and whether the trailer is overloaded. Runs in your browser; nothing is sent or stored.
Inputs
Result
Fill the form and press Calculate.
Cargo capacity = GVWR minus unloaded weight. A trailer with a 7,500 lb GVWR and a 5,800 lb unloaded weight can carry 1,700 lb, and that has to cover fresh water, propane, batteries, gear and everything you add.
Worked example
GVWR 7,500 lb, unloaded 5,800 lb: capacity 1,700 lb. Add 30 US gal of water (250.2 lb), 7 US gal of propane (29.7 lb), 600 lb of gear and 100 lb of extras: 979.9 lb used, which is 57.6% of capacity. That leaves 720.1 lb.
How it works
Cargo capacity = GVWR - unloaded weight; remaining = capacity - (water + propane + gear + extras). GVWR is the maximum loaded weight the manufacturer allows for the trailer. Unloaded weight often leaves out options, batteries, propane and water, so use the weights on the trailer's own label, or weigh the trailer on a scale.
This tool does not check axle or tire limits: a trailer can be under its GVWR and still overload one axle or tire if the load is lopsided. See the Trailer Tire Load Calculator for the tire check.
Sources opened 2026-10-08: Gross vehicle weight rating - Wikipedia. Planning aid only, not professional, engineering or safety advice. Your vehicle, trailer, tire, battery and boat manuals and the weight labels on your equipment come first; when in doubt, weigh it or ask a qualified professional.
FAQ
What is trailer payload?
Payload, or cargo carrying capacity, is the weight you can add to the trailer: the GVWR minus the unloaded weight.
What is GVWR?
The gross vehicle weight rating is the maximum loaded weight the manufacturer allows for the vehicle or trailer, including the trailer itself, fluids and cargo.
Does water count as cargo?
Yes. Fresh water weighs about 8.34 lb per US gallon (1 kg per litre), so a 40 gallon tank carries about 334 lb when full.
Why is my real payload smaller than the brochure says?
Brochure dry weights usually leave out options, batteries, propane and dealer-installed items. Weigh it or read the weight label.
What if I am over capacity?
Remove weight, empty water before travel, or move to a trailer with a higher GVWR. Do not tow an overloaded trailer.