Excavators are sold and hired by operating weight, and the weight is shorthand for reach, dig depth and how much the machine can lift at the end of the boom. A rental ladder runs from roughly 1 ton up to 50 tons, though any single yard usually covers a slice of it rather than the whole range.
Weight is the label the trade uses
The rungs most counters recognise are the 1 to 2 ton compacts, the 3 ton class that does most residential work, the 5 to 8 ton mid compacts, the 13 to 15 ton machines that handle drainage and roadworks, the 20 ton general contractor size, and heavy classes above 30 tons that live at regional branches.
Dig depth is what the class buys you
Very roughly, a 1 ton machine reaches around 6 feet down, a 3 ton around 10, a 5 ton around 12, a 14 ton around 20 and a 20 ton machine deeper still. Work out the invert level you actually need first, add for bedding and working room, then pick the class that clears it comfortably.
Transport quietly caps the class you can use
Machines up to a few tons move on a plant trailer behind a suitable truck. Above that a lowbed and a licensed driver are needed, which adds cost each way and needs somewhere to unload safely. On a tight urban lot, the practical limit is often what can be delivered rather than what would dig fastest.
Tail swing and the space beside the trench
Larger machines swing a counterweight well past the tracks, so the working envelope is wider than the machine. Zero and reduced tail swing versions exist in the compact and mid classes and are worth asking for beside a wall or a boundary. Tell the yard what is standing next to the dig, not only how deep it goes.
Questions people ask about sizes of excavators
What size excavator do I need to dig a foundation trench?
For a domestic strip footing, a 1.5 to 3 ton machine usually suits, provided access allows it. Depth and bucket width matter more than raw size. Tell the yard the trench depth, width and length and they will point at a class quickly.
Is a bigger excavator always faster?
Only if the site lets it work. A larger machine that cannot turn, cannot be delivered or has to shuffle constantly moves less material than a smaller one with room. Access and swing space decide productivity on constrained sites more often than bucket capacity does.
How is excavator size measured?
By operating weight in tons, which includes the machine as configured with a standard bucket and a full tank. Two machines of the same weight can differ in reach and lift, so check the dig depth and the lift chart if the job is near the limit of a class.