Inputs

Tow vehicle (from sticker on driver's door jamb)

Gross Vehicle Weight Rating — truck's max loaded weight.
Empty weight from spec sheet.
Gross Combined Weight Rating — truck + trailer max.

In the truck

Sum of body weights of everyone riding.
Tools, gear, dog crate, etc. in truck.

Trailer

Full fresh tank ≈ 8.3 lb/gal. 30 lb propane = 30 lb. Plus all your stuff.
TT/Travel Trailer: ~12-15%. 5th wheel: ~20-25%.

The four numbers that actually matter

Tow ratings on the sticker board are marketing. The numbers that keep you legal, insured, and alive are on the door-jamb sticker and the trailer's GVWR plate:

  • GVWR — the most loaded weight your truck alone is rated for. Includes you, passengers, fuel, gear, AND tongue weight from the trailer. Exceeding this is the most common (and most dangerous) overweight scenario.
  • Payload — GVWR minus curb weight. The actual capacity for everything you load into the truck.
  • GCWR — truck + trailer combined. Almost never the binding constraint on modern trucks.
  • Tow rating — the manufacturer's max trailer weight, calculated assuming a 150 lb driver, no passengers, no cargo. Real-world tow capacity is always less.

Why payload usually fails first

A typical 1500-class half-ton truck might be rated to tow 11,000 lb but only have 1,500 lb of payload. A 9,000 lb 5th wheel with 22% pin weight puts 1,980 lb of pin weight in the bed — before you add a cargo, hitch, or passengers. The math doesn't work, and you'll see this everywhere on RV forums.

Tongue/pin weight rules of thumb

  • Travel trailer / bumper pull: 12-15% of GVW. Less than 10% causes sway.
  • 5th wheel: 20-25% of GVW.
  • Toy hauler with motorcycles in back: load shifts; weigh both unloaded and with toys.
Critical safety note

An overweight tow rig handles unpredictably, has reduced braking, can void your insurance, and may exceed the rating of your tires (most blowouts come from being overloaded plus underinflated). Always weigh on a CAT scale before a long trip. The cost is $13 and it's the best safety dollar you'll ever spend.

Frequently Asked Questions

What does GVWR mean on my truck?
GVWR = Gross Vehicle Weight Rating. It's the maximum the truck can weigh with everything in or on it: passengers, fuel, gear, hitch, and the trailer's tongue/pin weight pressing down on the bed or hitch. Exceeding GVWR is what overloads tires, brakes, axles, and frame — and gets your insurance claim denied.
My truck is rated to tow 13,000 lb. Why does this calculator say no?
Tow rating assumes only the driver in the truck (typically 150 lb) and an empty bed. As soon as you add passengers, gear, a hitch, propane tanks, or anything else, available payload drops. For a 5th wheel, the pin weight (20-25% of trailer GVW) lands directly in the truck bed, often putting you over GVWR before you even hit the road. The calculator checks both.
Should I weigh my rig?
Yes, every RVer should weigh at least once. CAT scales at most truck stops cost about $13 and tell you (1) total truck weight, (2) total trailer weight, (3) front axle, (4) rear axle. Reweighing after major changes (new equipment, tank levels, kids in the back) keeps you out of trouble.
What's a weight distribution hitch and do I need one?
A WDH redistributes some of the trailer's tongue weight from the rear axle of the truck back to the front axle and the trailer axles. This restores the truck's natural loaded posture, improves steering control, and prevents headlight aim being thrown skyward. Almost any travel trailer over 5,000 lb GVW should use one. WDH does not increase your truck's tow rating — it just lets you safely use it.

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About our math & sources

Every default and formula in this calculator is grounded in published manufacturer specs, industry standards, or peer-reviewed measurement. Where we make assumptions, we tell you what they are so you can adjust.

  • GVWR, GCWR, payload definitions. From the SAE J2807 standard (Society of Automotive Engineers) and FMVSS Part 567 (Federal Motor Vehicle Safety Standards). Same definitions used on every door-jamb sticker in the U.S.
  • Tongue weight percentages. RVIA (RV Industry Association) recommendations: 10–15% for travel trailers, 20–25% for fifth wheels. Going below 10% causes trailer sway.
  • Why tow ratings are misleading. Manufacturer tow ratings assume a 150 lb driver, no passengers, and an empty bed. Real-world capacity is always lower once you load the truck. Same caveat applies to all major manufacturers (Ford, GM, Ram, Toyota).
Disclaimer. This calculator provides estimates only. Real-world results depend on equipment efficiency, environmental conditions, and installation quality. Always verify against your equipment's spec sheets and consult a licensed installer for safety-critical decisions.