Trailer Ball Size Table
| Ball diameter | Shank diameter | Typical max GTW |
|---|---|---|
| 1 7/8 in (47.6 mm) | 3/4 in | 2,000 lb |
| 1 7/8 in (47.6 mm) | 1 in | 2,000 lb |
| 2 in (50.8 mm) | 3/4 in | 3,500 lb |
| 2 in (50.8 mm) | 1 in | 6,000 lb |
| 2 in (50.8 mm) | 1 1/4 in | 6,000 lb |
| 2 5/16 in (58.7 mm) | 1 in | 6,000 lb |
| 2 5/16 in (58.7 mm) | 1 1/4 in | 10,000 lb |
| 3 in (76.2 mm) | 2 in | over 10,000 lb |
Four ball diameters cover essentially every trailer on North American roads: 1-7/8 in for light loads, 2 in as the universal middle, 2-5/16 in for heavy campers and equipment trailers, and the 3 in agricultural/gooseneck giant. The table pairs each ball with its shank (the threaded stud that bolts into the drop receiver) because the rating lives in the pair, not the ball: a 2 in ball on a 3/4 in shank tops out at 3,500 lb, while the same 2 in ball on a 1-1/4 in shank is good for 6,000 lb. The coupler on the trailer tongue is built to exactly one of these diameters, stamped or cast into its housing - that marking, not the eye, is the first thing to read.
The arithmetic behind the columns is conservative by design: a towing system is a chain of ratings (ball, shank, ball mount, hitch head, vehicle tow rating, trailer brakes), and the weakest link governs. The ball-and-shank numbers here match the hitch-class ladder - Class I to 2,000 lb, Class II to 3,500, Class III to 6,000, Class IV to 10,000 - so a parts-counter decision is: read the coupler size, pick the matching ball with a shank rated at or above the trailer's gross weight, and remember tongue weight (the vertical 10-15 percent pressing down on the ball) is included in those numbers, not extra.
How to use
- Read the coupler first: the trailer tongue's socket is stamped with its required ball diameter (1-7/8, 2, 2-5/16) - buy that size, never eyeball it, because a 1/8 in gap feels snug and shakes loose down the road.
- Match the shank to the load: heavier trailers need the fatter 1-1/4 in shank (6,000-10,000 lb range), and the receiver tube's internal width (1-1/4 in vs 2 in) must accept the ball mount that shank comes on.
- Torque the lock nut to spec and re-check after the first miles: a ball is only as rated as its installed clamp load, and the lock washer-or-flange nut is what keeps a rattling tongue from spinning the ball loose.
Frequently asked questions
Why does the same ball size have different weight ratings?
Because the ball is only half of the rated pair. Take the 2 in ball: on a 3/4 in shank it is rated 3,500 lb gross trailer weight, on a 1 in shank 6,000 lb, and on the fat 1-1/4 in shank still 6,000 lb but with heavier-duty mounts and hardware around it. The failure mode the rating guards against is bending and shearing of the shank plus the clamping joint, and shank cross-section grows with diameter faster than load grows - which is why the 10,000 lb tier lives exclusively on 1-1/4 in shanks. The practical discipline: never quote a ball's rating without its shank, and when a used ball mount has no stamping legible, treat the whole assembly as unrated and buy the rated pair new. The table's rows are combinations for exactly this reason - the counter question is not what ball fits, but what ball-and-stud pair carries the trailer.
How bad is towing with a 1-7/8 ball on a 2 inch coupler?
It is the classic and dangerous mismatch, because the sizes are 1/8 in (3.2 mm) apart - the coupler will drop onto the smaller ball, latch, and even seem fine on a driveway test. Under way, the oversized coupler socket hammers on the ball with every bump, wearing an egg-shaped pocket that eventually lets the coupler jump off entirely - and a trailer departing at highway speed is a worst-case accident, which is why every state requires safety chains as the backup that this scenario routinely tests for real. The tell-tale beforehand is sound and rock: a correct fit has minimal slop and no clunk when you lift the tongue; a mismatched pair knocks audibly. The two sizes look similar because they are similar - which is exactly why the coupler stamping, not the eye, decides. If a coupler is unlabeled, measure its socket bore with calipers and match the table row before the first tow.
What is the difference between hitch classes and ball ratings?
Classes rate the hitch structure bolted to the vehicle; ball ratings cover the ball-and-shank in the table; and the vehicle's own tow rating caps everything. Class I hitches (to 2,000 lb, sometimes 2,500) pair with 1-7/8 or 2 in balls; Class II (3,500) with 1-7/8 or 2 in; Class III (6,000-8,000) with 2 or 2-5/16; Class IV (10,000) with 2-5/16. The system rule stays the weakest link: a Class IV hitch with a 2 in ball on a 3/4 in shank is a 3,500 lb rig no matter what the receiver could theoretically hold. Tongue weight - the downward 10 to 15 percent of trailer gross weight - rides on the same ratings and is why a 5,000 lb trailer with 700 lb tongue weight can overload a ball mount that passes the pull test. Sizing is a ladder walk from trailer gross weight up through ball, mount, hitch, vehicle - and the lowest rung sets the limit.
Why is there a 3 inch ball, and do I need one?
Almost certainly not - the 3 in (76.2 mm) ball is the agricultural and heavy-gooseneck outlier, rated above 10,000 lb and used on farm implements, large equipment trailers and heavy gooseneck couplers where a pintle or fifth-wheel would otherwise be the answer. It is absent from consumer retail for a reason: ordinary campers, utility trailers and boat rigs live entirely on the first three sizes, and the heavy-trailer world mostly skips balls altogether in favor of gooseneck couplers and fifth-wheel plates that spread load over the truck bed instead of hanging it off a stud. If a seller offers a 3 in ball for a passenger-vehicle hitch, that is a mismatch by definition - no Class I-IV receiver pairs with it. The useful takeaway from the table's big row is scale: loads beyond the 2-5/16 range change the coupling technology, not just the ball diameter, and that decision belongs to a hitch shop, not a parts aisle.