There is no fixed upper size for a stump that can be ground, because the grinder works across a wide stump in sections and moves as it goes. What really limits a very large stump is time, access, the stump's height and shape, and rock or metal in the wood, and the rare stump past those limits is lifted out whole instead.
Why there is no simple maximum
People picture the grinder covering the whole stump from one position, so a stump wider than the machine sounds impossible. That is not how it works. The cutting wheel swings side to side in an arc, called the sweep, and takes a layer off with each pass. When one strip is down, the machine moves forward or to the side and starts the next. A big stump is simply more strips. Published specifications for tracked grinders list sweeps from about three feet to more than six, depending on the size of the machine, and a stump wider than that is handled by repositioning.
What counts as big
Most yard stumps are a foot or two across. Big starts somewhere around three feet at the flare, and the giants in this part of the world are old oaks, big pines and tulip poplars. NC State Extension describes tulip poplar as one of the largest native trees in North America, with record trees reaching trunk diameters of eight to ten feet. Few yard stumps come close, but stumps four and five feet across at the flare do turn up on older properties and farmland. And the work climbs much faster than the width: double the width and there is roughly four times as much face to cut.
Height is its own limit
Specifications also give a maximum cutting height above ground, roughly two to three and a half feet across common tracked models. A stump left taller than that is worked down from the top, which is slower, or cut lower with a saw first. Tall stumps are common after storms and on lots where trees were felled in a hurry. If you have a say in how the tree is cut, ask for a low, flat stump. If it is already tall, include a photo from the side with something for scale, so the height is as clear as the width.
Shape, rock and hidden metal
Size is rarely what stops a grind. Shape is more often the problem. A stump with several trunks fused together, a stump grown around a boulder, or one sitting on a ledge of rock has parts the wheel cannot reach or should not touch, because carbide teeth do not cut stone. Old fence wire, nails, chain and spikes buried in the wood slow everything down and can damage teeth. Hollow stumps are the opposite case: big on the outside but less wood to grind. Any of these is worth mentioning in your photos, because they change the job more than a few extra inches of width.
Access matters more for big stumps
A large stump is often a large old tree's stump, and large old trees are often in awkward places: against a house, on a bank, behind outbuildings or at the edge of a steep yard. Size makes access harder in a second way, because a big stump throws a lot of chips and needs room around it for the machine to step across it. A narrow tracked grinder gets through ordinary yard gates, so reaching even a big stump is usually possible. Photos of the route in, from where a trailer can park, settle it. There is a short guide to sizing up a stump for an estimate as well.
When the answer is to lift it out
Some stumps are better removed than ground, and size alone is seldom the reason. A blown-down tree leaves a root plate on edge, with nothing flat to grind. A stump on a building pad has to come out whole anyway. A stump grown around rock may come out more cleanly with a machine than with a wheel. In those cases a machine digs the whole root mass free and carries it off, and the hole behind it gets filled. If a stump is genuinely too big to grind economically, you will be told so and offered the removal option.
Grindings from a very large stump
A big stump produces a surprising volume of grindings: shredded wood mixed with soil, fluffed up to several times the volume of the wood it came from. Raked back into the hollow, it will settle for a long time as it rots. For a lawn, hauling most of it off and filling with soil gives a better result. In a natural area, spreading it out works fine. Decide before the day, because handling that volume is part of the job. Large stump grinding covers big stumps from measuring through to clean-up.
Common Questions
Can a stump grinder handle a stump five feet across?
Yes, in most cases. The machine grinds a wide stump in strips and moves across it, so width alone rarely rules a stump out. It takes much longer than a small stump and produces a large pile of grindings. Rock, hidden metal, height or very tight access matter more than the width.
Is there a maximum stump height for a stump grinder?
Each machine has a maximum cutting height above ground, roughly two to three and a half feet on common tracked grinders. Taller stumps are worked down from the top or cut lower first. Send a side photo with something for scale if yours was left tall.
Does a hollow stump grind faster than a solid one?
Usually, because there is less wood to cut. The shell still has to be ground below grade, and a hollow stump can hide rocks, soil and debris inside it, which slow things down. Mention any hollow or rot in your photos.
What to Do Next
Big stump? Stretch a tape across its widest point at the soil, photograph it, add a picture of the access and your town, and ring (828) 574-4474 for a straight answer on grinding versus removal.