RV Towing Payload Calculator: Tongue Weight, and What It Costs You

Tongue weight is 10–15% of your loaded trailer weight, all of it comes out of your tow vehicle’s door-sticker payload, and it is the tongue figure — not the trailer figure — that decides which hitch you need.

Every towing calculator that ranks for this either asks you to type in your tongue weight, which is the one number you probably do not have, or ignores it along with the payload sticker entirely. This one works it out, spends it, and turns it into a hitch rating.

It will not tell you that anything is safe. It gives you the margin in pounds, the arithmetic that produced it, and the list of limits it has not looked at.

The number nobody gives you

Open the two strongest calculators on this search and you find the same hole in both.

Equal-i-zer’s own hitch size calculator — which ranks, and which is made by a hitch manufacturer — asks for three figures: gross trailer weight, tongue weight, and cargo weight. It requires you to already know your tongue weight. rvtowingcalc’s payload calculator does the same thing. mintrv, the top-ranked result, does not address tongue weight at all.

That is a strange gap, because tongue weight is the hardest of the three to obtain and the only one that cannot be read off a sticker. It needs either a dedicated scale or two passes at a truck stop.

It is also the number that everything else depends on. It sets how much of your payload is gone before anyone gets in the truck. It sets which hitch model fits. And below the band it is what makes a trailer sway.

The sticker, not the brochure

The payload figure to use is on the driver’s door jamb, on the Tire and Loading Information label, and it reads:

The combined weight of occupants and cargo should never exceed XXX kg or XXX lbs.

That wording is not a manufacturer’s choice. It is required by 49 CFR 571.110 S4.3(a), and the regulation defines the underlying figure as the rated cargo and luggage load plus 68 kg for each designated seating position — which is where the 150 lb per seat in the calculator above comes from.

Two things follow, and both catch people out.

It is not the brochure number. The label is printed for your vehicle as built. Every option on it — the sunroof, the bigger wheels, the four-wheel drive, the heavier trim — has already been subtracted. Two trucks of the same model can differ by several hundred pounds of payload.

Occupants are in it. The word “combined” is doing real work: your passengers are not separate from the budget, they are part of it. Add the tongue weight and you are spending one number four ways.

The band is the answer, not a number to round

Equal-i-zer’s guidance is direct: “Always calculate your trailer’s tongue weight at 10–15% of its loaded gross weight.” Weigh Safe publishes 9–15% for the same measurement. The calculator uses Equal-i-zer’s, because the hitch is one of the ones in our records.

The temptation is to take the middle and move on. Do not, because the ends are further apart than they look:

Loaded trailer	At 10%	At 15%	Spread
4,000 lb	400 lb	600 lb	200 lb
6,000 lb	600 lb	900 lb	300 lb
7,000 lb	700 lb	1,050 lb	350 lb
9,000 lb	900 lb	1,350 lb	450 lb

On a 7,000 lb trailer the band is 350 lb wide. That is more than two adults, out of a payload budget that on a lot of half-tons is around 1,500 lb.

Which is why the calculator above has a third answer besides inside and over: it depends on how you load it. When the band straddles your sticker figure, a single-number calculator has to pick a side, and it will be wrong about half the time. The honest output is both ends and the distance between them.

Where you land inside the band is not a property of the trailer. It is decided by where the heavy things sit relative to the axles — a generator moved from the rear bumper to the front locker can shift it by a percentage point.

Size on the tongue, not on the trailer

Here is the part that is genuinely not written down anywhere on this search, and it falls out of the manufacturers’ own model ranges.

Both bar-hitch makers build their ladders at exactly ten to one.

• Equal-i-zer: 400/4,000, 600/6,000, 1,000/10,000, 1,200/12,000, 1,400/14,000, 1,600/16,000 — tongue weight against gross trailer weight, every rung at 10%.
• Blue Ox SwayPro: 350/3,500 at the bottom, 2,000/20,000 at the top. Same ratio.

Now put that next to the 10–15% band. A hitch chosen to match your trailer weight is rated for a tongue weight of exactly 10% — the very bottom of the range the same manufacturer tells you to expect.

So a 6,000 lb trailer loaded at 13% puts 780 lb on the ball. Its trailer weight points straight at the 600/6,000 Equal-i-zer. Its tongue weight needs the 1,000/10,000. Size it on the trailer and you have bought a hitch under-rated on the figure that actually matters.

The calculator above tests both ratings, which is why it will show you a hitch labelled “big enough for the trailer, not for the tongue” rather than quietly dropping it. Seeing that named is the point.

And the rating is not your tongue weight either

There is one more step, which Equal-i-zer publishes and no page ranking for the sizing query repeats:

Calculate an approximate hitch load by adding the trailer tongue weight and about 1/3 of the cargo weight that is in the back of your tow vehicle … This calculated hitch load is closer to what the minimum tongue weight rating needs to be for the hitch.

Equal-i-zer’s own worked example is 825 lb of tongue weight plus 250 lb — a third of 750 lb in the bed — for a 1,075 lb hitch load. That does not fit the 1,000/10,000 model. The cargo in the back moved the answer up a size.

The calculator applies this, so the rating it prints is a hitch load rather than a tongue weight. It assumes the cargo you entered rides behind the rear axle rather than in the cabin, which is what the field asks for.

The other two halves of “what size” — the shank rise or drop, and your receiver’s own weight-distributing rating — are a different job, done with a tape measure rather than a scale: what size weight distribution hitch do you need.

And if the reason you are here is that the trailer actually swayed, tongue weight is only one of the causes, and the hitch is fourth on a list that starts free: why does my trailer sway.

One number this calculator produces has a second use worth knowing about. Your trailer’s loaded weight, and its axle count, decide which brake controllers are rated for it — and the ratings differ more than the marketing suggests, from two axles at one end to four at the other. Do I need a brake controller runs your axle count and brake current against every record we hold; if you already know you need one, the P3 and the Tow-Pro Elite are the usual shortlist, and one of them stops at three axles.

Andersen is the exception, and it is worth knowing why. Its entry model is 1,400/10,000 — 14%, not 10% — so it carries more tongue headroom at the bottom of its range than either bar hitch. The trade is at the other end: Andersen makes nothing below 10,000 lb gross at all, so on a small trailer the only Andersen you can buy is one rated far above it — there is no way down the range. The two are covered head to head in Andersen vs Equal-i-zer.

Before you drive on

• Load the trailer exactly as you tow it — water, gear, propane, bikes.
• Everyone who normally rides is in the vehicle, with the usual cargo aboard.
• Release the weight distribution bars for pass 1. With them engaged the hitch has already moved load back to the trailer, and the answer is not tongue weight.
• Note the fuel level. A tank of diesel is well over 100 lb and it changes between passes if you fill up.

Pass	Platform 1 — steer	Platform 2 — drive	Platform 3 — trailer
A Pass 1 — coupled, bars released Whole rig on the scale. Steer on platform 1, drive on 2, trailer on 3.	Steer lb	Drive lb	Trailer lb
B Pass 2 — tow vehicle alone Unhitch, leave the trailer clear of the scale, drive back on.	Steer lb	Drive lb	not on the scale

Then, before you leave

1. Tongue weight (A steer + A drive) − (B steer + B drive) = ______ lb The change in the tow vehicle's total weight. Not the drive axle difference — that figure is bigger than the tongue weight and is the error most worksheets bake in.
2. Loaded trailer weight A trailer + tongue weight = ______ lb Platform 3 carries only the trailer's own axles. The tongue is resting on the tow vehicle, so it is weighed on platforms 1 and 2 and has to be added back.
3. Tongue percentage tongue weight ÷ loaded trailer weight × 100 = ______ % Equal-i-zer publishes 10–15% of loaded gross weight; Weigh Safe publishes 9–15%. Under the band the trailer is prone to sway; over it, the tongue is eating the tow vehicle's payload.
4. Payload spent tongue weight + people + cargo + hitch = ______ lb Against the door sticker figure — "the combined weight of occupants and cargo should never exceed…" — which is the one required by regulation and is not the brochure payload.

Worked, so the sheet is checkable

Pass 1 reads 3,180 steer, 4,240 drive, 5,960 trailer. Pass 2 reads 3,420 steer, 3,160 drive. Tongue weight is (3,180 + 4,240) − (3,420 + 3,160) = 7,420 − 6,580 = 840 lb. Loaded trailer weight is 5,960 + 840 = 6,800 lb. That is 840 ÷ 6,800 = 12.4% — inside the band.

The shortcut in circulation would have taken 4,240 − 3,160 = 1,080 lb and called that the tongue weight. It is 240 lb too high, because 240 lb is what the hitch levered off the steer axle: 3,420 − 3,180. Sized on 1,080 lb you would buy a hitch a full model larger than you need.

Platform numbering as published by CAT Scale. The tongue weight formula is Weigh Safe's — "towing vehicle weight while attached minus towing vehicle weight" — and the tongue percentage band is Equal-i-zer's published 10–15%. Verified 24 August 2026. No prices appear here because CAT Scale does not publish its rates. rvtrove.com/towing/rv-towing-payload-calculator/

The shortcut that overstates your tongue weight

The worksheet records both axles on both passes, and that is deliberate, because the method most RV sites print does not.

The common version says: weigh the rig coupled, weigh the truck alone, subtract the two rear axle figures, and that difference is your tongue weight. It is not. It is bigger.

The hitch sits behind the rear axle, so it works as a lever. Loading the ball pushes the rear axle down and lifts the front axle. The rear axle therefore gains the tongue weight plus whatever it takes off the front — and the front-axle loss is invisible if you only wrote down the rear number.

The subtraction that gives tongue weight is the change in the tow vehicle’s total weight. Weigh Safe states the formula plainly: “Towing vehicle weight while attached − towing vehicle weight = tongue weight.”

In the worked example on the sheet the two methods differ by 240 lb on a 840 lb tongue — a 29% overstatement, and enough to push you a full model up the hitch ladder for no reason.

What the hitches are rated for

Model	Tongue weight	Gross trailer weight	How the range is stepped	Smallest model	Hitch weight	Buy
Equal-i-zer 10K	1,000 lb maximum	10,000 lb maximum	10% at every rung	4,000 lb (the 400/4,000)	106.5 lb for the 10K kit, per etrailer's measured shipping weight. Equal-i-zer does not publish a figure	Check price(opens in a new tab)
Blue Ox SwayPro 1000	1,000 lb	10,000 lb	10% at both ends	3,500 lb (the BXW0350)	Not published by Blue Ox, and we have found no measured figure we trust — unlike the Equal-i-zer, where etrailer publishes a shipping weight	Check price(opens in a new tab)
Andersen No-Sway 10K	1,400 lb	10,000 lb	14% at the bottom, 10% at the top	10,000 lb — nothing smaller	Under 60 lb, per Andersen	Check price(opens in a new tab)

The hitch weight column is there because it is a payload item and almost nobody prints it. Note also that it is the column with the most missing data: Equal-i-zer publishes no figure, so the 106.5 lb is etrailer’s measured shipping weight and is labelled as such, and Blue Ox publishes nothing at all.

Where this goes wrong

Using the dry weight as the trailer weight. The brochure figure routinely excludes dealer-fitted options, batteries, propane and sometimes the awning. Water alone is 8.34 lb a gallon — a 40 gallon tank is 334 lb. The calculator adds these back when you have no scale ticket, and labels the result a floor. The same pounds count against the trailer’s own GVWR, which is a separate limit from your truck’s payload — the cargo capacity calculator checks that side.

Using the brochure payload instead of the door sticker. They are different numbers and the difference is the options on your particular vehicle.

Forgetting the hitch. It is 60 to 200 lb sitting on the payload budget before you have loaded anything, depending which one you buy.

Measuring tongue weight with the bars engaged. You will get a comfortable number that is not tongue weight.

Measuring it on a trailer that is not level. Tongue weight moves with the trailer’s attitude, so a rig that tows nose-high is putting less on the ball than the same rig sitting level — which is a sway problem rather than a payload saving. The ball mount drop calculator covers getting that right before you weigh anything.

Treating payload as the only limit. It is the one this tool checks and it is frequently the binding one on a half-ton — but the rear axle rating, the tires and the combined weight rating all exist, and on some rigs one of those runs out first. Tires have a second limit that has nothing to do with load: the tire age calculator reads the date code, and a trailer tire usually times out long before it wears out.

Sizing the hitch on trailer weight. See above. The makers’ ladders are built at 10% and the band goes to 15%.

Questions worth answering