Towing Capacity Calculator
Max loaded trailer weight from GCWR, curb weight, and payload, with tongue weight.
What it does
Towing capacity is subtraction, not a sticker number. The gross combined weight rating (GCWR) caps the truck and trailer together with everything loaded; subtract the truck's own curb weight and everything riding in it, and what remains is the fully loaded trailer you can pull.
Tongue weight is the piece of the trailer that sits on the hitch, typically targeted at 10 to 15 % of trailer weight. Too little and the trailer sways and fishtails; too much and it overloads the receiver, the rear axle, and the truck's steering.
Tongue weight also counts as payload, so it spends truck capacity twice: once as part of the trailer, and again on the hitch. That interaction is why an 8,700 lb trailer with a 1,044 lb tongue can push a half-ton truck over its payload rating before it ever hits the published tow number.
Every figure here is arithmetic on ratings you supply, not a certified towing rating. Axle ratings, hitch class, frontal area, brakes, and tires can cap you lower, so weigh the loaded rig at a scale before trusting the math.
How to use
- Find GCWR on the door jamb sticker or in the towing guide.
- Enter the truck's curb weight.
- Enter passengers, gear, and anything else riding in the truck.
- Pick a tongue weight target, usually 12 %.
- Read the max loaded trailer weight.
- Read the tongue load and GCWR share.
Formula
- GCWR
- Gross combined weight rating: truck plus trailer, both fully loaded.
- curb
- Truck's empty weight with full fluids.
- load
- People, gear, and cargo in the truck.
- tongue
- Percent of trailer weight carried on the hitch; 10 to 15 % is the usual window.
'Fully loaded trailer' includes the trailer's own cargo, water, and gear, not just its empty shell. Tongue weight counts against the truck's payload and GVWR as well as the GCWR, so it consumes capacity twice. Trailering guidance from state agencies and Army safety material places tongue weight at 10 to 15 % of gross trailer weight.
Worked example
Example: 15,000 lb GCWR pickup
GCWR 15,000 lb, curb 5,500 lb, passengers and cargo 800 lb, tongue target 12 %.
- Trailer budget: 15,000 - 5,500 - 800 = 8,700 lb.
- Tongue: 0.12 x 8,700 = 1,044 lb.
- Share: 8,700 / 15,000 = 58 % of GCWR.
- At 10 % the tongue would be 870 lb; at 15 %, 1,305 lb.
- Tool shows 8,700 lb, 1,044 lb, 58 % of GCWR.
Reference table
| Tongue target | Hitch load | Note |
|---|---|---|
| 5 % | 435 lb | Below window: sway risk |
| 10 % | 870 lb | Lower edge |
| 12 % | 1,044 lb | Common target |
| 15 % | 1,305 lb | Upper edge |
| 20 % | 1,740 lb | Overloads axles and steering |
Limits
- Sticker ratings are ceilings; axle ratings (GAWR), hitch class, and receiver limits can cap you lower.
- Assumes the trailer, its cargo, water, and gear all fit inside the result.
- Frontal area, wind, altitude, grades, and drivetrain derate real-world ability.
- Weigh the loaded rig at a scale; every number here is arithmetic on your inputs, not a certified rating.
Common mistakes
- Comparing trailer weight to the advertised tow rating while ignoring payload.
- Forgetting that gear in the truck cuts trailer capacity pound for pound.
- Loading the trailer tail-heavy to hit a scale number; under 10 % tongue it sways.
- Exceeding the receiver's own tongue limit even when total weight fits.
- Counting tongue weight once: it also eats truck payload and GVWR.
Try it yourself
Quick checks. Answers sit tucked under each question.
GCWR 16,000, curb 5,500, cargo 1,000?
9,500 lb of loaded trailer.
Same setup at 10 % tongue?
950 lb on the hitch.
Cargo rises to 1,500 lb?
9,000 lb of trailer; at 12 % the tongue is 1,080 lb.
Questions
GCWR versus GVWR versus curb weight?
GCWR caps truck plus trailer combined, GVWR caps the truck alone, and curb weight is the empty truck. Towing math runs GCWR minus curb minus payload.
Where do I find GCWR?
The driver's door jamb sticker, the owner's manual towing table, or the manufacturer's towing guide for your exact trim, axle ratio, and options.
What tongue weight is correct?
10 to 15 % of loaded trailer weight; 12 % is a common target. Verify with a tongue scale or a scale split at a truck stop.
Does payload really subtract from towing?
Yes. GCWR covers everything moving, so 10 lb of canoe in the bed costs 10 lb of trailer allowance.
Can I tow at the maximum?
Only with the right hitch, brakes, tires, and loading. Ratings assume a base truck with a driver and typical options, not a loaded cab.
What about trailer brakes and sway control?
Heavier trailers need their own brakes, and state rules often require them past 2,000 to 3,000 lb. Weight-distributing hitches tame sway on heavy tongue loads.