Weighing
How do you actually weigh a trailer and tow vehicle?
Every capacity figure on this site, and every one on your own vehicle, is compared against a real weight, not a printed one. Curb weight, dry weight and tow rating are all measured once at a factory under specific conditions. The weight that matters on a given trip is the one on the scale that day, with the water tanks, the propane, the cooler, the bikes and the passengers all where they will actually ride.
There are two ways to get real numbers: a public scale built for the job, and a dedicated tongue weight scale you use in your own driveway. They answer different questions. A public scale gives you total weights and, at a truck stop scale with separate axle pads, individual axle weights. A tongue weight scale gives you one number, the downward force on the ball, more precisely than a public scale usually can.
Do both if you can. A public scale run once a season catches the big picture: is the trailer near its GVWR, is the tow vehicle near its payload, is the combined rig near the GCWR. A tongue weight scale catches the number that changes every time you load differently, and it is the number most directly tied to whether the trailer sways.
Why the brochure number is the wrong number
A trailer's advertised dry weight, properly called unloaded vehicle weight, is the trailer as it left the factory: no water, no propane, no batteries, no cargo, and none of the options a dealer bolted on afterward. A tow vehicle's advertised curb weight is similarly bare. Neither number is what leaves your driveway.
Water is the single biggest gap. It weighs 8.34 lb per gallon, so a 40 gallon fresh tank alone adds roughly 334 lb, and a 50 gallon tank adds about 417 lb. Two full propane cylinders add close to 74 lb once the steel bottles are counted, and a single battery adds another 50 lb or more. None of that is in the printed dry weight, and all of it is on the trailer the day you tow it.
On the tow vehicle side, passengers, a full bed, a hitch and anything bolted on since the factory (running boards, a bed cover, a toolbox) all come out of payload, and none of it is in the curb weight printed on the window sticker years ago. Weighing is how you replace two numbers that were never true for your rig with two numbers that are.
How do you weigh at a public scale?
- Weigh the tow vehicle alone first. Loaded exactly as you will tow: full fuel, every passenger who is coming, every bag already in the cab or bed. This is your true loaded tow vehicle weight, and if the scale has separate axle pads, note the front and rear axle weights separately.
- Hitch up and weigh the combined rig. Pull the whole rig, tow vehicle and trailer together, onto the scale as one weighing. This total is your combined weight, the number to compare against GCWR.
- Weigh the tow vehicle again with the trailer still hitched. Some scales let you weigh just the tow vehicle's axles while the trailer sits on its own pad behind it. If yours does, this reading, minus the tow vehicle's unhitched weight from step one, is your tongue weight directly.
- Unhitch and weigh the trailer alone. The trailer's own axles only. Subtract this from the combined total in step two and you get the tow vehicle's hitched weight a second way, which should be close to step three and confirms your tongue weight.
- Do the subtraction. Combined weight minus trailer-alone weight equals the tow vehicle's weight while towing. That figure minus the tow vehicle's unhitched weight from step one is your tongue weight. The same combined weight minus the unhitched tow vehicle weight from step one equals your trailer's true loaded weight.
- Write the numbers down and keep them. A loadout that repeats trip to trip, same bikes, same water routine, same passengers, will produce a similar tongue weight each time. A loadout that changes needs a fresh weighing, not a guess based on the last one.
What each weighing actually tells you
Four different numbers come out of the same trip to the scale, and each one gets compared against a different rating on your own vehicle. Mixing them up is the most common weighing mistake.
The tow vehicle's own weight, hitched and unhitched, is what you compare against payload, and the combined total is what you compare against GCWR.
Published standard A published, traceable figure: a standards body, a federal regulation or a manufacturer specification states it.
| What you weighed | How you get it | Compare it against |
|---|---|---|
| Tow vehicle, unhitched | Direct reading, step one | Curb weight plus this equals nothing useful alone; subtract from step three for tongue weight |
| Tow vehicle, hitched | Direct reading if the scale supports it, or combined minus trailer-alone | Payload rating on the door jamb sticker |
| Trailer, alone | Direct reading with the trailer unhitched | Trailer GVWR on its certification label |
| Combined rig | Direct reading, both hitched together | GCWR on the tow vehicle's own certification |
| Tongue weight | Hitched tow vehicle weight minus unhitched tow vehicle weight | The 10 to 15 percent conventional band, and your receiver and hitch ratings |
A scale ticket reports what was on the pad. It does not know your payload rating, your GVWR or your GCWR, those come off your own stickers, and comparing the two is a step you have to do yourself.
Weighing tongue weight at home instead
A dedicated tongue weight scale gets you the single most important number without a drive to a truck stop. A scale such as the Sherline LM 2000 sits under the coupler with the trailer loaded and level, and reads the downward force directly, in pounds, on a dial or a digital display. The full procedure, including the lever method that works with an ordinary bathroom scale, is its own page: a digital scale removes the parallax error that makes a dial hard to read lying on the ground, which is worth knowing before you buy one.
The home method and the public scale method should agree within a few percent. If they do not, weigh again before trusting either number, because a tongue weight scale set on uneven ground or a trailer that was not level at the moment of the reading both produce numbers that look precise and are not.
Sources
- Water weight of 8.34 lb per US gallon, standard reference figure
- Propane cylinder tare and fill weights, standard reference figures for 20 lb barbecue cylinders
Frequently asked questions
Where can I find a public scale that weighs a trailer?
Most truck stop CAT scales will weigh a personal tow rig for a small fee, and many now have an app that reports axle-by-axle weights on your phone before you even get out of the truck. Some public works departments and grain elevators also run scales open to the public. Call ahead if you are unsure whether they take non-commercial vehicles.
Do I need to weigh every single trip?
No, but weigh again any time the loadout changes meaningfully: a new battery, a full water tank instead of an empty one, a generator added to the front bay, or a different group of passengers. A loadout that repeats closely from trip to trip will produce a tongue weight and a total weight close to what you measured before.
Can I just use the numbers from my owner's manual instead of weighing?
The manual gives you ratings, the ceilings you are not supposed to cross. It cannot tell you what your specific rig weighs today, loaded with your specific gear. Weighing gives you the actual number to compare against those ceilings, and the two together, rating and actual weight, are what a safe towing decision needs.
Why did my trailer weigh more than the brochure said?
Because the brochure figure is the unloaded factory weight, with no water, no propane, no batteries and none of the options a dealer added. A 50 gallon fresh tank alone is over 400 lb full. Trailers routinely weigh a thousand pounds or more above the brochure figure once loaded the way people actually travel.
What is the difference between weighing at a scale and using a tongue weight scale?
A public scale gives you total and, with separate pads, axle weights for the whole rig, which you need for GVWR, GCWR and payload checks. A dedicated tongue weight scale gives you one number, the downward force on the ball, more conveniently and often more precisely, since it is a purpose built instrument rather than a truck stop platform.
My tongue weight and public scale numbers do not agree, which one do I trust?
Reweigh both before trusting either. A tongue weight scale on uneven ground, or a trailer that was not level when read, produces an inaccurate number that still looks precise. Small differences of a few percent are normal between methods; a large gap usually means one of the two readings was taken incorrectly.
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Researched, not professional advice. This page is compiled from published standards, manufacturer towing guides and product specifications, and owner-review consensus, not hands-on testing. Figures described as a rule of thumb are towing convention rather than published standards, and they are labelled that way wherever they appear. Nothing here overrides your own ratings. Work your payload sum before your tow rating, because payload is the limit that actually binds on most half ton trucks and nearly every SUV. Load a conventional trailer to 10 to 15 percent tongue weight and a fifth wheel to 15 to 25 percent pin weight, and never lighter: a tail heavy trailer is what starts sway. Weigh the rig loaded rather than trusting a brochure dry weight. A weight distribution hitch and a set of air bags both restore ride height and control, and neither one raises a single rating. Trailer brakes are required by state law above a threshold that varies by state, and a breakaway battery that has quietly gone flat is the normal condition of most trailers on the road.