How to weigh your trailer (the CAT scale method)

Why weigh at all

Brochure dry weights are measured before the dealer options, the battery, the propane, the water, and everything you packed. Real loaded travel trailers routinely run far heavier than their listed dry weight — and tongue weight is nearly impossible to eyeball. If you tow regularly and have never crossed a scale, your margins are folklore.

Certified truck-stop scales (CAT Scale is the big network, at major US truck stops) weigh each axle group on a separate platform in one pass. That's what makes the method below work.

The five steps

1. Load the rig the way you actually tow. Weigh what you really pull: water and propane at travel levels, gear loaded, family in the truck. An empty-trailer number flatters you and lies to you.
2. First pass — weigh the whole rig hitched. Pull onto the truck-stop scale so the truck's steer axle, drive axle, and the trailer axles each sit on a separate platform. Stop, follow the intercom instructions, and collect the ticket. You now have three axle weights and a combined total.
3. Second pass — weigh the truck alone. Drop the trailer (most truck stops offer a cheaper re-weigh within a short window), pull back on with just the truck, and get the second ticket: steer and drive axle weights without the trailer.
4. Do the math. Trailer gross weight = combined total from pass one minus truck-alone total from pass two. Tongue weight = truck-alone weights subtracted from the truck's hitched weights (steer + drive from pass one minus steer + drive from pass two). Payload used = truck-alone total minus the curb weight on your door-jamb label.
5. Check the numbers against your limits. Put the measured trailer weight and tongue weight into the tow-match calculator along with your door-jamb ratings — it checks tow rating, GCWR, payload, and hitch class at once and names the limit that binds.

Reading the two tickets: a worked layout

Pass one gives you three numbers — steer axle, drive axle, trailer axles — plus their total. Pass two gives you steer and drive without the trailer. From those five numbers you get everything that matters:

• Trailer gross weight (GVW): pass-one total − pass-two total. Compare it to the trailer's own GVWR sticker and to your vehicle's honest max trailer weight.
• Tongue weight: (pass-one steer + drive) − (pass-two steer + drive). The trailer axles don't carry it — your truck does. Aim for 10–15% of trailer weight on a conventional trailer; the tongue weight calculator checks your percentage.
• Payload check: pass-two total (truck loaded, no trailer) tells you what the truck weighs with people and gear; hitched, the tongue weight lands on top of that. Together with the door-jamb payload figure, the payload calculator shows what's left.
• Rear-axle sanity check: compare the drive-axle reading from pass one against the RAWR (rear axle weight rating) on your door-jamb label. A rig can be inside its tow rating and still overload the rear axle if the tongue is heavy and the bed is full.

Weighing light trailers at home

For small utility, boat, and pop-up trailers, tongue weight is the number worth measuring at home. A dedicated tongue-weight scale under the coupler (jack the trailer to towing height, level, wheels chocked) reads it directly. The classic bathroom-scale lever setup also works for light tongues, but a bathroom scale maxes out quickly and a beam-and-pipe rig has to be set up exactly right — for anything heavier than a small trailer, the scale trip is cheaper than the error.

How often to re-weigh

Once with your normal travel load is the baseline. Re-weigh when something meaningful changes: a new trailer or truck, a cargo-carrier or generator added to the tongue, water tanks you now travel full instead of empty. Loading position moves tongue weight a lot — if you rearrange where the heavy stuff rides, the old tongue number is void. See the tongue weight guide for how placement shifts the balance.

Related: trailer weight estimator · tongue weight guide · what is GVWR.