About TowCapacityCalc
TowCapacityCalc is a set of free towing calculators and reference guides. The calculators apply published towing formulas to ratings and weights that you enter, and report which limit runs out first. Nothing here reads your vehicle — every number comes from you, from a manufacturer towing guide, or from an official state source that is linked on the page.
Why the site exists
Towing capacity is one of the most misread figures in the automotive world. A truck advertised at 12,000 lb of towing is quoting the best-equipped version of that model carrying almost nothing. Once a family, their gear, and a trailer’s tongue weight are aboard, the limit that actually binds is usually payload — a smaller number printed on a label in the driver’s door jamb that most owners have never read.
The gap between those two numbers is where overloaded rigs come from. Every calculator on this site is built to close it: enter what you have, and the tool shows you the first limit you run out of and by how much.
What the calculators do
They apply standard towing arithmetic to the values you enter. There is no proprietary model and no hidden adjustment:
The tools then compare each result against the ratings you entered and report the smallest remaining margin — which is usually payload rather than tow rating.
What they do not do
- They do not look up your vehicle’s ratings from a VIN, a registration, or a licence plate.
- They do not measure anything. Tongue weight from a percentage is an estimate; a scale ticket is a measurement.
- They do not model heat, grade, altitude, wind, tire condition, or brake condition.
- They do not replace the labels on your vehicle and trailer, which are the ratings that legally apply.
Where the data comes from
Manufacturer towing guides
The truck database is transcribed from towing guides published by Ford, GM, Ram, Toyota, Nissan, and Jeep. Each model page records the guide used and the date it was last checked.
State statutes and DOT pages
Every trailer brake, breakaway, and safety-chain figure links to the state statute, DOT, DMV, or public-safety page it came from, with a verification date.
Published towing formulas
The percentage ranges used for tongue and pin weight are the conventions published in owner manuals and hitch manufacturer guidance, not values we derived.
Full detail is on the methodology page, and every source is listed on the sources page.
What published tow ratings are tested against
Most current light-duty tow ratings reference SAE J2807, an industry test procedure that makes ratings comparable between manufacturers. It is worth knowing what it covers, because it explains what a tow rating is and is not:
- A measured grade climb, launch and merge performance, braking, and handling stability with a trailer attached.
- A defined test vehicle load — which is why published maximums assume a nearly empty vehicle.
This site references the standard to explain published ratings. It does not test vehicles and is not affiliated with SAE International or any manufacturer.
Who writes this
One named person writes and edits every guide on this site, maintains the calculators and the truck data, and reads the state-law records against the sources linked on each page — working to the editorial policy. There is no anonymous editorial team here, and no borrowed credentials: this site does not test vehicles, and it says so wherever a figure comes from someone who does.
- 50
- guides written and edited
- 138
- statute-cited rules across 49 states
- 5
- corrections published with what the page used to say
The middle figure is the part worth checking. Each of those rules was read out of a named statute or agency page, and the citation and official link travel with the claim on the page where it appears — rather than sitting in a source list at the bottom. Where no official source could be found, the page says so instead of guessing.
If you find a figure that disagrees with an official source, please tell us — corrections are published with the date they were made and what the page used to say.
A note on the 80% convention
Many experienced towers plan to roughly 80% of whichever limit binds, leaving 15-20% in reserve for mountain grades, crosswinds, heat, brake fade, and the difference between how you planned to load and how you actually loaded. It is a widely used planning convention rather than a legal requirement, and the tools on this site flag setups that go beyond it so you can make that call deliberately.