Check if your vehicle can safely tow a trailer based on GVWR, tongue weight, and payload.
Enter your vehicle's curb weight, GVWR, and GCWR, plus the loaded trailer weight and its tongue weight, and the tool runs the three checks that decide whether the combination is safe to tow: combined weight against GCWR, tongue weight plus occupants and cargo against payload, and tongue load against the 10-15% band. It returns a pass or fail verdict with the binding limit named, computed entirely in your browser. The surprise most users hit: the advertised max tow rating assumes a nearly empty truck, so a crew cab with passengers and gear typically runs out of payload long before it runs out of towing capacity.
A concrete input and expected output from the current implementation.
Input
Curb weight 5,600 lb; GVWR 7,200 lb; GCWR 14,000 lb; occupants and cargo in the truck 850 lb; trailer loaded 7,400 lb; tongue weight 950 lb
Expected output
Payload capacity: 1,600 lb (7,200 - 5,600). Payload used: 1,800 lb (850 + 950) - OVER by 200 lb. FAIL. Combined weight: 5,600 + 850 + 7,400 = 13,850 lb - under the 14,000 lb GCWR, margin 150 lb. PASS. Tongue load: 12.8% of trailer weight - inside the 10-15% band. PASS. Verdict: not safe to tow as loaded. Payload is the binding limit; remove at least 200 lb of occupants or cargo from the truck, or shift trailer cargo forward to reduce tongue weight.
The trailer fits the GCWR easily, but the 950 lb of tongue weight plus 850 lb of occupants exceeds the 1,600 lb payload, so the truck itself would be overweight. The payload check, not the combined-weight check, is what sinks this combination.
Payload capacity is GVWR minus curb weight. Everything the truck carries counts against it: occupants, gear in the cab and bed, the hitch, and the trailer's tongue weight. The tool subtracts each item in turn and reports the remaining margin, and if the total goes negative the truck is over its GVWR even though the trailer alone looks fine.
Three numbers decide the verdict. Gross combined weight (loaded truck plus loaded trailer) must stay under GCWR. Tongue weight should sit between 10% and 15% of the loaded trailer weight: too little invites trailer sway, too much overloads the rear axle. The tool reports each check as pass or fail with its margin, so the binding limit is visible.
Because the brochure rating assumes a nearly empty truck. Passengers, gear, and the hitch all consume payload before the trailer is connected, and tongue weight consumes more of it. When those exceed payload capacity, the truck is overweight even though the trailer is well under the advertised maximum. Trim the load in the truck, or find a lighter trailer.
It appears in both checks, but once in each. The loaded trailer weight used for the combined-weight check already includes the tongue weight, and the same tongue weight also counts against the truck's payload, because the hitch presses it onto the truck. The tool applies it once in each place, which is how the ratings are intended to be used.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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