Tongue Weight Scale Calculator: The Method, a Worked Example and the Limits

Tongue Weight Scale Calculator is the part of towing maths most people skip, and the part that causes the most trouble when it is wrong. Tongue weight is the downward force the trailer puts on the tow hitch, and the working rule is 10 to 15 percent of the trailer's loaded weight. Too little and the trailer sways; too much and the tow vehicle's steering goes light and its rear suspension bottoms out. This page shows the formula, works through examples at several trailer weights, and explains how to measure it with a scale.

Never exceed your vehicle's GVWR, GCWR or payload. Check the owner's manual and the door-jamb sticker for the ratings that apply to your exact vehicle, and treat every figure on this page as a worked example unless it comes from your own vehicle's plates.

tongue weight scale calculator: The method: the lowest of three ratings

Taking tongue weight scale calculator as the case in point: Three ratings decide what you may tow, and the answer is the smallest of them: the vehicle's tow rating, the tow-bar rating and the trailer's ATM — the aggregate trailer mass, the most the loaded trailer is rated to weigh. Here the worked example uses 6,500 lbs for the vehicle, 6,000 lbs for the tow bar and 6,500 lbs for the trailer ATM, which makes the towing capacity 6,000 lbs. Those numbers are examples, not ratings for any real vehicle: read the three figures off your own manual and plates and the same step gives your answer. Each rating guards a different part of the rig — the vehicle's engine, transmission, brakes and cooling; the tow bar and its mounting; the trailer's axles, tyres and brakes — so the weakest link sets the limit.

There is a second layer of limits behind the tow rating. The loaded vehicle may not exceed its GVWR, the vehicle-plus-trailer combination may not exceed its GCWR, and the payload — the gap between kerb weight and GVWR — has to cover passengers, cargo and the tongue weight of the trailer. That last point is the one people miss: the hitch load is carried by the vehicle, so a heavy trailer shrinks the payload left for everything else. Pass the tow-rating check and still fail GCWR or payload, and the combination is overloaded. Check all three against the figures for your exact vehicle in the manual and on the door-jamb sticker.

Where to find your ratings for tongue weight scale calculator

Four plates and documents carry the whole answer. The owner's manual lists tow ratings by engine, axle ratio and configuration and states GVWR and GCWR. The driver's door-jamb sticker gives the GVWR and payload for your exact vehicle as built. The tow-bar rating plate sits on the bar or by the receiver. The trailer's compliance plate shows its ATM and tare weight. Read all four, and if two sources disagree, use the lower figure and ask a dealer to confirm for your VIN. Ratings shift with engine, axle ratio, cab, bed length and tow package, so a figure for a different configuration — or one copied from a forum — is not a substitute.

Tongue weight: the 10 to 15 percent rule for tongue weight scale calculator

Tongue weight should be 10 to 15 percent of the trailer's loaded weight. For a 3,500 lbs trailer that is 350 to 525 lbs, with about 438 lbs as a good middle target. Below 10 percent the trailer is prone to sway, because there is not enough downward force on the hitch to keep it tracking straight; above 15 percent the tow vehicle's rear suspension is overloaded, the steering goes light and the headlights point at the sky. The fix for wrong tongue weight is loading, not guessing: move heavy items forward of the trailer axle to increase it, or behind the axle to reduce it, and re-weigh. Never fix sway by adding speed — slow down, and check the loading before the next trip.

tongue weight scale calculator: How to measure tongue weight

On this page, tongue weight scale calculator is the case in point: The accurate way is a tongue-weight scale under the coupler with the trailer level and loaded as it will travel. A bathroom scale and a lever can work for lighter trailers, but the reading is only as good as the setup, so a proper scale is worth it for anything heavy. Measure with the trailer loaded as it will travel — water tanks, gas bottles, luggage and all — because an empty trailer tells you nothing about the loaded figure. Record the number, divide it by the trailer's loaded weight, and check the percentage is inside 10 to 15 percent. If it is not, reload and measure again.

Worked example: the three ratings and the payload check for tongue weight scale calculator

Take a 3,500 lbs loaded trailer as the example. The vehicle's tow rating is 6,500 lbs, the tow-bar rating is 6,000 lbs and the trailer ATM is 6,500 lbs. The towing capacity is the lowest of the three: 6,000 lbs. The trailer's tongue weight at 10 to 15 percent is 350 to 525 lbs, and the middle of that range — about 438 lbs — is a good target. With an example payload of 1,800 lbs, the tongue weight leaves 1,362 lbs for passengers and cargo. If the passengers and luggage weigh more than that, the combination is overloaded even though the trailer is inside the tow rating, and something has to come off — either the trailer load or the vehicle load. That is the whole check in one paragraph: lowest of three, then tongue weight, then payload, then GCWR. Do it with your own numbers before every trip, because the answer changes every time the load changes.

tongue weight scale calculator: Tongue weight table

For tongue weight scale calculator, the point is this: The tongue-weight range below is 10 to 15 percent of the loaded trailer weight, with 12.5 percent in the middle as a practical target. Find your trailer's loaded weight in the first column and read across. Weigh the trailer as it will travel — guessing the weight makes the whole table useless.

Loaded trailer weight (lbs) 10% tongue weight 12.5% tongue weight 15% tongue weight
3,500 350 438 525
5,000 500 625 750
6,000 600 750 900
7,000 700 875 1,050
10,000 1,000 1,250 1,500

The four checks, in order for tongue weight scale calculator

Check What to compare Passes when
Tow rating Trailer weight against the lowest of the three ratings Trailer is at or below the lowest rating
Tongue weight Tongue weight vs 10–15% of trailer weight Inside the range
Payload Tongue weight + passengers + cargo vs payload Total is at or below payload
GCWR Vehicle + trailer loaded weights vs GCWR Combined weight is at or below GCWR

Common mistakes for tongue weight scale calculator

  • For tongue weight scale calculator, the point is this: Skipping the brake check on the trailer. A trailer's brakes need testing before every trip, not just at service time — a seized or disconnected trailer brake puts the whole stopping job on the tow vehicle.
  • For tongue weight scale calculator, the point is this: Taking the highest rating and ignoring the other two. The vehicle rating, the tow-bar rating and the trailer ATM are all limits, and the lowest one decides — a strong vehicle with a light tow bar is limited by the tow bar.
  • For tongue weight scale calculator, the point is this: Trusting a figure quoted for a different year, engine or configuration. Tow ratings change with engine, axle ratio, cab and tow package, so only the numbers for your exact vehicle count.
  • Taking tongue weight scale calculator as the case in point: Loading the trailer tail-heavy to reduce tongue weight. Putting weight behind the axle lightens the hitch, but it is the fastest way to make a trailer sway, and sway at speed is far more dangerous than a heavy hitch.

Related calculations for tongue weight scale calculator

Taking tongue weight scale calculator as the case in point: For the next step, these pages apply the same method to a closely related question — or hand the arithmetic to the calculator.

Putting your figure to work for tongue weight scale calculator

For tongue weight scale calculator, the point is this: Putting the figure to work means doing the check with your own numbers before every trip, not once when you buy the trailer. Weigh the loaded trailer, read the three ratings off your own manual and plates, work out the tongue weight, and check the payload and GCWR. Write the four numbers down and keep them with the trailer's documents: the lowest of the three ratings, the tongue-weight range, the remaining payload and the GCWR headroom. When the load changes — a full water tank, an extra passenger, a different trailer — redo the check, because the answer changes with the load. That habit is what keeps a towing combination inside its limits on the road, not just on paper.

Frequently asked questions

How much trailer can I tow?

It depends on the lowest of your vehicle's tow rating, your tow-bar rating and the trailer's ATM, capped by GVWR, GCWR and payload. In this page's worked example the lowest rating is 6,000 lbs. Substitute your own three ratings and run the same check — the answer is specific to your vehicle and your trailer, not a general figure.

How do I work out my towing capacity?

Take the lowest of three ratings: your vehicle's tow rating, your tow-bar rating and the trailer's ATM. Then check the tongue weight is 10 to 15 percent of the trailer weight, and check the combination against GVWR, GCWR and payload. All four checks have to pass. The ratings come from your owner's manual, the door-jamb sticker, the tow-bar plate and the trailer plate — not from a figure quoted for a different vehicle.

What is trailer ATM?

On this page, tongue weight scale calculator is the case in point: ATM is the aggregate trailer mass: the maximum the trailer is allowed to weigh when fully loaded, set by the trailer manufacturer. It is on the trailer's compliance plate, and it is one of the three ratings in the lowest-of-three rule — your towing capacity can never exceed the trailer's ATM.

Where do I find my vehicle's tow rating?

Taking tongue weight scale calculator as the case in point: In the owner's manual, listed by engine, axle ratio and configuration, and on the door-jamb sticker and VIN plate for your exact vehicle. The tow bar has its own rating plate, and the trailer has a compliance plate showing its ATM. If the manual and the sticker disagree, use the lower figure and ask a dealer to confirm for your VIN.

Can I exceed my towing capacity?

No. The tow rating is a maximum set by the manufacturer for the vehicle's engine, transmission, brakes and cooling, and exceeding it increases braking distances, overheats the transmission, reduces stability and can be illegal. It can also void warranty coverage and give an insurer a reason to refuse a claim. If the trailer is heavier than the lowest of the three ratings, you need a different vehicle, a different tow bar or a lighter load. That is the point this page works through for tongue weight scale calculator.