CAT Scale Weighing Guide
Every number on a towing spreadsheet is an estimate until a scale confirms it. A scale ticket costs a few dollars, takes fifteen minutes, and replaces every assumption about how your rig is actually loaded.
Written by Imtinan Farooq, Editor, TowCapacityCalc · Updated
Quick answer
Weigh the rig loaded exactly as you travel. A CAT scale platform reports steer axle, drive axle, and trailer axle separately, so one pass gives you loaded vehicle weight, trailer weight, and axle loads. A second pass with the trailer uncoupled gives you tongue weight by subtraction. Compare each figure against GVWR, GAWR front and rear, GCWR, and the trailer’s GVWR.
Worked example: reading a three-pass ticket
A half-ton and a travel trailer, weighed loaded for a trip. GVWR 7,100 lb, front GAWR 3,700 lb, rear GAWR 4,100 lb, GCWR 15,000 lb, trailer GVWR 7,600 lb.
| Line item | Weight | Where the number comes from |
|---|---|---|
| Pass 1 — steer axle | 3,180 lb | Against 3,700 lb front GAWR: 520 lb margin |
| Pass 1 — drive axle | 3,760 lb | Against 4,100 lb rear GAWR: 340 lb margin |
| Pass 1 — trailer axles | 6,140 lb | Trailer weight less tongue weight |
| Vehicle total, coupled | 6,940 lb | Against 7,100 lb GVWR: 160 lb margin |
| Pass 3 — vehicle alone | 6,050 lb | Trailer uncoupled and parked clear |
| Tongue weight | 890 lb | 6,940 − 6,050 |
| Loaded trailer weight | 7,030 lb | 6,140 + 890, against 7,600 lb trailer GVWR |
| Gross combination weight | 13,080 lb | Against 15,000 lb GCWR: 1,920 lb margin |
Every rating passes, but the margins are uneven: 1,920 lb spare on GCWR and only 160 lb on GVWR. The tongue weight came out at 12.7% of the loaded trailer — close to the 13% estimate this time, which is worth knowing rather than assuming.
What a scale actually confirms
A ticket gives you five things no estimate can: real loaded vehicle weight against GVWR, real front and rear axle loads against GAWR, real trailer weight against its own GVWR, real combined weight against GCWR, and — by subtraction — real tongue weight.
Why estimates drift
Percentage rules assume a typical weight distribution. A front-kitchen or front-bedroom floor plan can put tongue weight several hundred pounds above a 13% estimate. Curb weights quoted online are for a base configuration that may not match your trim, drivetrain, or options. Each error is modest; stacked, they are the difference between compliant and overloaded.
The three-pass method
Pass one: whole rig on the scale, coupled — steer, drive, and trailer axles all read at once. Pass two: pull forward so the trailer wheels are off the platform, still coupled. Pass three: uncouple, park the trailer clear, and weigh the tow vehicle alone. Ask for a re-weigh on passes two and three so you pay the lower rate.
- Pass 1 gives gross combination weight and trailer axle weight.
- Pass 2 gives vehicle weight with tongue weight included.
- Pass 3 gives vehicle weight without the trailer.
- Tongue weight = pass 2 vehicle total − pass 3 vehicle total.
Reading the ticket against your ratings
Take five numbers off the labels first: GVWR, front GAWR, rear GAWR, GCWR, and trailer GVWR. Then line each up against the ticket. Record the margin on each line rather than a simple pass or fail — the size of the margin tells you how much room you have for the gear you have not packed yet.
Using the scale to set a weight-distribution hitch
Weigh the steer axle uncoupled, then coupled with the hitch tensioned. A well-adjusted setup restores the front axle to at or near its uncoupled figure. If the front is still light, add tension; if it is heavier than uncoupled, back it off. This turns hitch adjustment from guesswork into a measurement.
When to weigh again
After any significant change: a new trailer, a new tow vehicle, a bed toolbox, a generator, a different loading routine, or a long trip with full tanks when you usually travel empty. Once a season is a reasonable rhythm for a rig that stays the same.
What to compare on the ticket
| Ticket figure | Compare against | Where the rating is printed |
|---|---|---|
| Steer axle weight | Front GAWR | Certification label, door jamb |
| Drive axle weight | Rear GAWR | Certification label, door jamb |
| Vehicle total, coupled | GVWR | Certification label, door jamb |
| Trailer axle weight + tongue | Trailer GVWR | Trailer data plate |
| All axles combined | GCWR | Owner’s manual or towing guide |
| Tongue weight by subtraction | Hitch tongue rating | Label on the receiver |
| Axle weight vs tire capacity | Tire load rating | Tire sidewall and door label |
Record the margin on each line, not just pass or fail. A 100 lb margin and a 2,000 lb margin are very different situations.
Frequently asked questions
How do I measure tongue weight at a scale?
Weigh the tow vehicle’s axles with the trailer coupled but the trailer wheels off the platform, then weigh the tow vehicle alone with the trailer uncoupled. The difference between the two vehicle totals is the tongue weight.
What does a CAT scale weigh session cost?
A first weigh is typically a few dollars, with re-weighs on the same visit charged at a lower rate. The re-weigh rate is what makes the multi-pass method inexpensive.
Should I weigh with full or empty tanks?
Weigh the rig exactly as you travel. If you normally leave with a full fresh-water tank, weigh it full — that is 334 lb on a 40-gallon tank and it changes tongue weight noticeably.
What do the three platform readings mean?
Steer axle is the tow vehicle’s front axle, drive axle is its rear axle, and the third platform reads the trailer axles. Their sum is the gross combination weight to compare with GCWR.
Why does my front axle get lighter when I hitch up?
Tongue weight sits behind the rear axle, which levers weight off the front. A weight-distribution hitch restores it. Comparing the steer-axle figure coupled and uncoupled shows exactly how much was transferred.
Before you trust any number here
Every figure on this page is a planning estimate. The binding limits are printed on your vehicle: the driver-door payload sticker, the certification label, the hitch label, the tire sidewalls, and the trailer data plate. Weigh the loaded rig before a long trip.
Read the full verification checklistExplore this topic cluster
Moving from brochure numbers to real loaded truck, trailer, axle, tongue, and combined weights.