Towing Capacity Calculator
Find what you can actually tow once the truck is loaded.
Advertised tow ratings assume an empty vehicle with a single driver. Tongue weight, GVWR, axle ratings and hitch class all impose separate limits — the lowest of them governs.
How this calculator works
max trailer = GCWR − curb weight − passengers and cargo
The tow rating on the brochure is what the truck can pull with nothing in it. Every pound of people, fuel and gear comes straight off that figure, which is why real capacity is often 1,500 lb less than advertised.
Switch the site to metric — the control is in the footer — and your inputs, your results and the tables below follow. The formula, the constants, the guidance text and the sources stay in US units on purpose: that is how the standards they come from are written, and restating them would detach each figure from the document you are meant to be able to check it against.
Where these numbers come from
- SAE J2807 (Performance Requirements for Determining Tow-Vehicle Gross Combination Weight Rating) 2020 — GCWR and how tow ratings are established
The edition matters as much as the number. Jurisdictions adopt code revisions on their own schedule, so verify which one applies where you are building.
Worked example
With gcwr 15000 lb, vehicle curb weight 6000 lb, passengers and cargo 800 lb, this calculator returns 8200 lb.
Real trailer capacity for common tow vehicles
Open any row to load it into the calculator above — the link carries the numbers with it, so it can go straight to a supplier or a crew.
| Job | Size | Maximum trailer weight |
|---|---|---|
| Mid-size SUV, family aboard | 11000 lb × 4800 lb × 900 lb | 5,300 lb |
| Half-ton pickup, driver only | 15000 lb × 5500 lb × 250 lb | 9,250 lb |
| Half-ton pickup, loaded bed | 15000 lb × 5500 lb × 1400 lb | 8,100 lb |
| Three-quarter-ton diesel | 25000 lb × 8000 lb × 1200 lb | 15,800 lb |
| One-ton dually | 32000 lb × 8600 lb × 1500 lb | 21,900 lb |
The brochure rating assumes an empty truck. People, fuel and gear all come straight off it.
Frequently asked questions
Why is my real towing capacity lower than advertised?
Published ratings assume an empty truck with a 150 lb driver. Add a family, a full tank, tools and a hitch and you can lose 1,500 lb of capacity before hooking anything up.
What is GCWR?
Gross Combined Weight Rating — the maximum the truck and trailer may weigh together, fully loaded. Subtract your actual loaded vehicle weight from it and what remains is your trailer allowance.
Why tow at only 80% of maximum?
It preserves braking distance, transmission temperature and control in crosswinds and on grades. Sustained towing at the limit is where transmissions and brakes fail, especially in hills.
Does tongue weight count against payload?
Yes, and it catches many people out. Ten to 15% of the trailer weight presses down on the hitch and counts toward the truck payload, so a 7,000 lb trailer puts 700 to 1,050 lb into the bed.