How to measure tongue weight without a scale
The 10–15% rule, four ways to measure, and how to fix it. Updated October 4, 2026.
Tongue weight is the downward force your trailer's coupler puts on the hitch ball. It's the single number that decides whether a trailer tows straight or wants to sway, and it changes every time you load the trailer differently. Here's how much you want, and every practical way to measure it.
How muchBathroom scaleTruck-stop scaleTongue-weight scaleYour phoneFixing itSafety
How much tongue weight do you want?
- Conventional (bumper-pull) trailers: about 10–15% of the loaded trailer's weight. A 5,000 lb travel trailer wants roughly 500–750 lb on the ball.
- Fifth-wheel and gooseneck trailers: their "pin weight" is higher, usually about 15–25%.
- Never more than the lowest rating among the hitch receiver (its label lists a maximum tongue weight), the ball mount, the ball and the vehicle (owner's manual).
- It counts against your payload. Tongue weight, passengers and cargo together must stay under the payload on the tire and loading sticker in the driver's door jamb.
| Method | What you need | Cost | Good for |
|---|---|---|---|
| Bathroom scale (+ board) | A bathroom scale; for heavier tongues a sturdy board and a short pipe | nothing extra | Small trailers directly; heavier ones with the lever method |
| Truck-stop scale | A certified public scale, two weighs | a small fee per weigh | The most complete picture: axle weights too |
| Tongue-weight scale | A dedicated gauge that sits under the coupler | roughly $100 and up | Repeated checks at home |
| Your phone | An iPhone and the Tongue Weight app | app | Quick checks at the campsite, with no equipment |
1. A bathroom scale
Light tongues (up to your scale's limit, often around 300 lb): set the scale on a box or blocks so that when the coupler rests on it the trailer sits level, at its towing height. Lower the coupler onto the scale with the jack and read it.
Heavier tongues: the lever method. A board spreads the load between the scale and a support, so the scale only sees part of it:
- Lay a short length of pipe (the support) and the bathroom scale a known distance apart: say 3 ft. Rest a sturdy board (a 4×4) across them.
- Note the scale's reading with just the board on it, and subtract it at the end.
- Rest the trailer's jack foot on the board at a known distance from the pipe: say 1 ft. Raise the jack until the coupler lifts off the ball, keeping the trailer level.
- Multiply the scale's reading (minus the board) by the span divided by the jack's distance from the pipe.
Example: a 3 ft span with the jack 1 ft from the pipe means the scale carries a third of the load. A reading of 210 lb (after subtracting the board) is a tongue weight of 210 × 3 = 630 lb.
2. A truck-stop scale
Certified public scales at truck stops weigh each axle group separately, which tells you more than tongue weight alone.
- Weigh 1, hitched: drive on with the truck's axles on the first platforms and the trailer's axles on the last. If you use weight-distribution bars, take this weigh with them unhooked.
- Weigh 2, truck alone: unhitch and weigh the truck by itself (a reweigh is usually cheaper).
- Tongue weight ≈ the truck's total (steer + drive axles) in weigh 1 minus its total in weigh 2.
It's the most complete check: you also get your axle loads and gross combined weight. The catch is the drive and the queue.
3. A tongue-weight scale
A dedicated tongue-weight scale is a hydraulic gauge that sits under the coupler (or under the jack). Lower the trailer onto it and read the dial. It's quick and repeatable at home; check its range against your trailer, and use it on firm, level ground with the trailer at towing height.
4. Your phone: reading how the truck settles
When a trailer's tongue goes on the hitch, the back of the truck goes down and the front comes up a little. The truck tips back by a small angle, proportional to the load. An iPhone lying still in the cab can measure that angle.
The angle alone doesn't say how many pounds caused it, because every truck's springs are different. So Tongue Weight uses you as a known weight:
- Calibrate empty: you sit on the open tailgate with the trailer still on its jack.
- Load: lower the coupler onto the ball.
- Calibrate loaded: you sit on the tailgate again with the trailer coupled.
Springs get stiffer as they're loaded, so the two calibrations bracket the true value, and the app reports that range rather than pretending to a single exact number. On ordinary leaf springs the range is tight. On suspensions that stiffen a lot it's wider, and if a 10% or 15% limit falls inside it, the app tells you to confirm at a scale.
Coming soon to the App Store
Light or heavy? How to fix it
- Too light: move heavy cargo forward of the trailer's axles, or carry fresh water if the tank sits ahead of them.
- Too heavy: move cargo back toward (not behind) the axles, take heavy items off the tongue, or carry less in the front storage.
- Know your heavy items: fresh water weighs about 8.3 lb per gallon (a 40-gallon tank is about 330 lb), a full 30 lb propane cylinder weighs about 55 lb, and a deep-cycle battery 50–70 lb.
- Re-check after changes. Tongue weight drifts every time the load moves.
What about weight-distribution hitches?
A weight-distribution hitch uses spring bars to shift part of the tongue weight forward to the truck's front axle and back to the trailer's axles. It doesn't change the tongue weight itself, so measure with the bars unhooked, then reconnect them to tow. Your hitch's manual explains how to set them.
Safety
- Chock the trailer's wheels before raising or lowering the tongue, and keep hands and feet clear of the coupler.
- Use level, firm ground. A slope or soft ground skews every method.
- Respect every rating: hitch receiver, ball mount, ball, vehicle tongue rating and payload. The lowest one is your limit.
- Near a limit, confirm at a certified scale. Bathroom scales and phones give estimates.