Trailer Sizes and Dimensions — What Size Trailer Do I Need?

"What size trailer do I need?" is really two questions: how much deck you need, and how much weight you're allowed to put on it. Most people only shop the first one, then discover the second at a scale house or on a hill. This guide covers how trailer sizes are written, what those numbers actually measure, what each common size holds, and where the payload ceiling sits — using real specs from the trailers we stock in Howell, Michigan.

Silver Ox 7x14 single axle aluminum utility trailer with rear ramp gate, showing the 7 ft by 14 ft deck, fenders and tongue that make up the overall trailer dimensions — A 7x14 — the size we get asked for most — Silver Ox 7x14 Aluminum Utility Trailer – Single Axle – Rear Ramp

How trailer sizes are written

A trailer described as 6x12 has a deck 6 feet wide and 12 feet long. Width always comes first. The number is the usable deck — not the overall size of the trailer.

That distinction matters more than people expect. Here's a real example from a Silver Ox 5x12 utility trailer:

Measurement	5x12 utility trailer
Deck size (the "5x12")	60" × 144" — 5 ft × 12 ft
Overall size	80" × 197" — 6 ft 8 in × 16 ft 5 in
Deck height	20"

Same trailer, two very different numbers. The advertised “5x12” is the deck only — the tongue and fenders are what actually have to fit in your garage. Note the axle sits aft of the deck centre, which is what puts 10–15% of the load on the tongue.

So a "12-foot" trailer needs about 16.5 feet of parking space, and a "5-foot-wide" trailer is nearly 7 feet across the fenders. The tongue adds roughly 4 to 5 feet of length; fenders add roughly 1.5 to 2 feet of width. Measure your garage, gate or parking spot against the overall dimensions, never the deck size.

The second number: payload

Deck size tells you what fits. It tells you nothing about what you're allowed to carry. Two numbers govern that:

GVWR — Gross Vehicle Weight Rating. The maximum the loaded trailer may weigh, trailer included. It's a legal limit, not a suggestion, and it's set by the axle, frame, tires and brakes together.
Empty weight (dry or curb weight) — what the trailer weighs before you put anything on it.

Payload = GVWR − empty weight. That's your real capacity. It's why a longer trailer can carry less than a shorter one on the same axle: a 7x14 weighs more empty than a 6x10, and both sit under the same 3,500 lb GVWR, so the bigger trailer eats more of its own budget.

You can watch that happen across our single-axle aluminum line — every one of these is a 3,500 lb axle, and payload drops as the deck grows:

Deck size	Axle	GVWR	Typical payload
6x10	Single 3,500 lb	3,500 lb	~2,810 lb
7x10	Single 3,500 lb	3,500 lb	~2,780 lb
5x12	Single 3,500 lb	3,500 lb	~2,900 lb
6x12	Single 3,500 lb	3,500 lb	~2,880 lb
7x12	Single 3,500 lb	3,500 lb	~2,717 lb
7x14	Single 3,500 lb	3,500 lb	~2,610 lb
7x16	Tandem 3,500 lb	5,722–7,000 lb	~4,400+ lb
7x18	Tandem 3,500 lb	7,000 lb	5,000+ lb

Figures are typical for the aluminum models we stock and vary by options — wood sides, side ramps and spare tires all subtract from payload. Check the individual listing for the exact numbers.

Where single axle ends and tandem begins

The jump from one axle to two is the single biggest decision in trailer sizing, and it's driven by weight, not length.

Single axle — one 3,500 lb axle, so 3,500 lb GVWR. Lighter, cheaper, easier to maneuver by hand, cheaper to re-tire. Practical ceiling around 2,600–2,900 lb of cargo.
Tandem axle — two axles, typically 7,000 lb GVWR. Roughly double the payload, far better road manners at highway speed, and it stays controllable if a tire fails. Heavier, and you're buying four tires and usually brakes.

Go tandem when your real load — machine plus fuel plus attachments plus the tools you always end up throwing on — clears about 2,500 lb, or when you'll spend real time above 55 mph. Brakes typically become a legal requirement as GVWR climbs; see Do I need electric brakes on my trailer? for the weight thresholds and Michigan rules.

What each size actually holds

Size	Typical use
4x6 / 5x8	Household moves, appliances, a push mower, dump runs. Fits most garages. Usually enclosed at this size.
5x10 / 6x10	One zero-turn mower, one ATV, yard waste, small landscaping. The classic homeowner trailer.
5x12 / 6x12	Mower plus trimmers and blowers, two ATVs nose-to-tail, furniture moves. The most versatile all-around size.
7x10 / 7x12	Full 7-foot width matters here — a side-by-side UTV, a compact tractor, or pallets that won't fit between 6-ft fenders.
7x14	Side-by-side plus gear, small skid steer, serious landscaping loads. Our most-requested size.
7x16 / 7x18	Multiple machines, jobsite equipment, heavy commercial use. Tandem axle territory.
16+2 / 22+2 car haulers	Written as deck plus dovetail — a 16+2 is 16 ft of flat deck plus a 2 ft dovetail, 18 ft total.

Two width rules worth knowing. A 6-foot-wide deck is not 6 feet between the fenders — the fenders intrude, so measure your machine's actual track width before assuming it fits. And most zero-turn mowers and side-by-sides need the full 7-foot width once you account for mirrors, decks and tire bulge.

Sizes we stock

Enclosed and dump trailers size differently

Enclosed cargo trailers add a third dimension: interior height. A 5x8 or 5x10 enclosed typically runs around 2,990 lb GVWR with roughly 2,000–2,080 lb of payload, and interior height decides whether you can stand up inside or only crouch. V-nose models add usable length at the front beyond the stated deck size.

Dump trailers are rated by both deck size and dump capacity, and they're heavy before you load them — the hydraulics, thicker floor and taller sides all count. A 5x10 tandem dump runs about 7,000 lb GVWR with roughly 1,895 lb of curb weight, leaving around 5,105 lb of payload and about 3,000 lb of dump capacity. A 6x12 goes up to about 10,200 lb GVWR. Because the trailer's own weight is so much higher, never size a dump trailer by deck dimensions alone.

How to measure a trailer you already own

Deck width — inside edge to inside edge of the usable deck, not outside the fenders.
Deck length — front of the deck to the rear, excluding the ramp gate when it's folded down.
Overall length — coupler to the rearmost point. This is your parking and storage number.
Deck height — ground to deck surface, loaded and unloaded. Ramp angle depends on it, and low-clearance machines care.
GVWR — read it off the VIN sticker on the tongue or front driver-side frame rail. Never guess it from size.

If the sticker is gone or unreadable, the axle is the next best clue — see How to identify your trailer axle.

Frequently asked questions

Is a trailer measured by deck or overall length?

By deck. A 6x12 has a 12-foot deck; overall length with the tongue is closer to 16–17 feet. Always check overall dimensions against your storage space.

What size trailer do I need for a zero-turn mower?

A 6x10 handles most single zero-turns. Go 6x12 or 7x12 if you're carrying trimmers, blowers and a second machine, and confirm your mower's deck width clears the fenders.

What size trailer for an ATV or side-by-side?

One ATV fits a 5x10 or 6x10. Two ATVs nose-to-tail need a 6x12. A full-size side-by-side really wants the 7-foot width — 7x12 or 7x14.

Do I need a tandem axle?

If your loaded weight approaches 2,500 lb, or you tow at highway speed regularly, yes. Below that a single axle is lighter, cheaper and easier to move by hand.

Why does a bigger trailer sometimes carry less?

Because payload is GVWR minus the trailer's own weight. On the same 3,500 lb axle, a 7x14 weighs more empty than a 6x10, so it has less capacity left for cargo.

How wide is a 6-foot trailer really?

About 6 ft 8 in to 7 ft overall across the fenders. The 6 feet refers to the deck.

Related guides

Not sure which size fits your machine? Tell us what you're hauling — make, model and whether it has a deck or attachments — and we'll tell you the size that works and the one that won't. AAA Trailer sells and stocks aluminum utility, enclosed cargo, dump and car hauler trailers in Howell, Michigan.