Four constraints decide this, and they frequently pull against each other. Work through them in order.
1. Dig Depth — Your Floor
Start here, because it's the one you can't compromise on. If the machine can't reach your required depth, nothing else matters.
| Class | Typical dig depth |
|---|---|
| 1 ton | ~5–6 ft |
| 1.5–2 ton | ~7–8 ft |
| 3 ton | ~8–10 ft |
| 4–5 ton | ~11–12 ft |
| 6–8 ton | ~14–15 ft |
Get your actual requirement from your building department, utility, or system designer — frost depth and burial codes vary enormously by region. Then add margin, because working at absolute maximum depth is slow and awkward.
2. Access Width — Your Ceiling
This is the constraint that pulls the other direction, and it's where most residential contractors get squeezed.
Measure your narrowest regular access: gates, side yards, between structures, and the pinch points past the entrance — AC units, meters, downspouts.
Bigger machines dig deeper and fit through fewer openings. If you work residential backyards, this constraint frequently overrides the depth you'd prefer.
Some machines address it directly. Retractable undercarriages narrow for access and expand for stability. Worth looking for if you're caught between depth and width.
3. Transport — The One People Forget
A 3-ton machine plus attachments plus trailer is a real load, and buyers routinely discover they need a bigger truck than they own.
Add up: machine operating weight + attachments + trailer weight. Then check against your trailer GVWR, axle ratings, tow vehicle towing capacity, and tow vehicle payload capacity. All four are separate limits.
Payload for tongue weight is frequently the binding constraint rather than tow rating.
If you'd need to buy a truck and a trailer to move the machine, that changes the purchase decision substantially.
4. Lift Capacity
If you're setting pipe, structures, or material, lift capacity matters — and it varies with reach and slew position, so a single headline number understates the complexity.
Ask for the lift chart, not just a maximum figure. Capacity over the side is typically lower than over the front.
Tail Swing: The Other Decision
Not a size question exactly, but it's decided at the same time.
Conventional tail swing — the counterweight extends past the tracks when slewing. Best stability and lift capacity for the weight, and generally lower cost. Requires room to rotate.
Reduced tail swing — overhang is minimized. A compromise.
Zero tail swing — the tail stays within the track width. You can work with your back against a wall or a fence, which is transformative on residential and urban sites. The trade is slightly less stability and lift for the same machine weight.
Kubota splits its entire lineup on this — the U-series is tight tail swing, the K-series is conventional. That tells you how significant the distinction is to buyers.
If you work residential backyards, urban infill, or against structures, zero tail swing is usually worth it. If you work open sites, conventional gives you more machine for the money.
Sizing by Application
| Work | Typical class |
|---|---|
| Backyard landscaping, tight access | 1–2 ton |
| Irrigation and drainage | 1.5–3 ton |
| General residential contracting | 3 ton |
| Septic systems | 4–5 ton |
| Utility installation | 3–5 ton, per burial depth |
| Footings and foundations | 3–5 ton, per frost depth |
| Pool excavation | 5 ton+ |
| Commercial and production | 6–8 ton |
| Demolition | 5 ton+, per structure |
| Land clearing support | 5 ton+ |
The Sweet Spot
The 3-ton class is where the largest share of the market lands, and for good reason: roughly 8–10 feet of dig depth covers most residential and light commercial work, the machines still trailer behind a properly rated pickup, and the used market is the deepest in the category.
If you're unsure and your work is general, that's the class to start looking at.
Buying Bigger vs. Smaller
Arguments for bigger: you'll grow into it; the job you can't do costs more than the machine you didn't need; depth and lift you don't have are hard limits.
Arguments for smaller: access is a hard limit too, and one you hit more often on residential work; smaller machines are cheaper to buy, transport, and own; and a machine that can't get to the work isn't doing it.
The honest answer for most residential contractors: access constrains you more often than depth does. For utility, septic, and commercial work, depth usually wins.
FAQ
What's the most versatile size?
3-ton, for most buyers. Best balance of depth, access, transport, and used-market depth.
Can one machine cover everything?
Rarely. Operations doing both tight residential and deep utility work frequently run two, or rent the size they don't own.
Should I get zero tail swing?
If you work against walls, fences, or in tight sites — yes. On open work, conventional gives more capability per dollar.
Cab or canopy?
Cab if you run year-round in a hard climate. Canopy saves real money and gives better visibility.
Do I need a thumb?
Close to essential for most work — handling debris, rock, pipe, and brush. Order it with the machine; retrofitting costs more.
What about a mini skid steer instead?
Different tool. Loaders carry and push; excavators dig and reach. If your work is material handling rather than digging, that may be the better machine. Compare →