Do Robot Mowers Cut the Edges? What Gets Left and How to Fix It
Updated 2026-10-10
Mostly, but not completely. A robot mower cuts right up to an edge it can drive over, such as a patio or driveway that sits level with the grass. Along a wall, fence or raised bed it leaves a narrow strip uncut. Plan on some trimming with almost any model, and expect a lot less of it if your edges are the right kind.
Why there's an uncut strip
The blades on a robot mower sit inside the body, set back from the outer shell. That's a safety design: it keeps the blades away from feet, paws and anything the mower bumps into (more in our pets and kids guide). The cost is that the cutting disc is narrower than the mower itself. When the shell is against a wall, the blades are still a few inches away from it.
Wire-free mowers add a second gap. When you map the lawn, the mower keeps a small safety margin from the boundary so that a positioning error doesn't send it into a flower bed or off a drop. Most apps let you adjust that margin, edge by edge.
Which edges it handles well
| Edge type | What to expect |
|---|---|
| Patio, driveway or path level with the lawn | The mower can ride its wheels onto the hard surface, so the blades reach the last of the grass. Little or no trimming. |
| Flush paver or brick mowing strip | Same as above. This is the fix for most problem edges. |
| Wall, fence, raised bed or steps | A strip of a few inches stays uncut. Needs a string trimmer. |
| Flower bed or mulch at lawn level | The mower stops short so it doesn't drive into the bed. A narrow strip stays uncut. |
| Drop-off, pond or pool | The boundary is set well back on purpose. Expect a wider strip. |
How to cut down on trimming
- Lay a mowing strip. A row of flat pavers or bricks set level with the soil along walls, fences and beds gives the mower somewhere to put its outside wheel. This is the single biggest improvement, and it works with every mower.
- Tune the boundary in the app. After the first few mows, move the boundary outward where the mower is stopping short of a safe, level edge. Many wire-free mowers also have a setting that lets them drive over flush hard surfaces.
- Turn on edge mowing. Many models run a lap around the perimeter as part of each job, or on a schedule. If yours has the option, use it. A perimeter lap gives a cleaner line than random or striped passes alone.
- Look at how the mower is built. Some mowers place the cutting disc off-center, closer to one side, or offer an edge-trimming attachment. These narrow the strip but don't remove it against a wall. Check the brand's spec sheet for the uncut-edge distance; when a brand states it, that number is the one to compare.
- Keep a string trimmer. A robot mower cuts a little, often, so the uncut strip grows at the same slow pace as the rest of the lawn. For most yards, a quick pass with a trimmer every week or two is enough.
Does the navigation type matter?
A little. The accuracy of the mower's positioning decides how close to the boundary it's willing to go. Under open sky, RTK models hold a tight line. Under heavy tree cover or beside a tall house, satellite positioning gets less precise, and a mower may keep a wider margin there. Vision and LiDAR models follow what they can see, which works well where the grass edge is clear. Our RTK vs LiDAR vs vision guide covers the tradeoffs.
Narrow strips of grass matter too. A passage between a fence and a bed that's barely wider than the mower may not get cut at all. See robot mowers and multiple zones for how mowers deal with passages and separate areas.
Should edges change which mower you buy?
Rarely. Lawn size and slope should decide the model, because a mower that's too small or can't climb your hill is a much bigger problem than a few minutes of trimming. Use the yard matcher to find mowers that fit, then compare edge features among the ones left.