What we compare
We only compare mowers sold on Amazon.com, where we earn a commission through our links. That means we don't cover every robot mower on sale. A mower sold only in other shops won't appear here, even if it suits your yard better.
What "Best overall" means
"Best overall" is our top pick from the mowers we compared on that page. It is not a claim that it's the best mower on the market. Each other pick names the yard it suits best.
Where our numbers come from
We read what each brand publishes for the US market. We use the list of numbers for each mower, the handbook, and the brand's help pages. We write each number down once and use it on every page. So the same mower shows the same numbers wherever you read about it.
We do not run mowers on a test lawn. We compare the numbers the makers publish, and we take a margin off them first. Then we measure your lawn from the map, so you can compare it with what the mower can handle.
The three numbers that matter most
- Area
- How much grass it can keep cut
- Slope
- How steep a hill the mower can climb
- Trees
- Whether branches over the lawn stop a mower working
Lawn area. Each mower is rated for a maximum lawn size. That figure assumes one open, simple lawn. If your lawn is bigger than that, the mower still works. But it cannot get around the whole lawn often enough, so the grass in the far corners grows long. So we take 20% off the brand's maximum lawn area before we say a mower suits your lawn. We cut it further if your lawn is an odd shape.
Slope. Every maker says how steep a hill its mower climbs, as a percentage. A 20% slope rises 20 ft for every 100 ft you walk. They measure it in the middle of the lawn, on dry grass, driving straight up the hill. Your hill is wet early in the morning, and the mower has to turn while it is on the hill. So we take 15% off the brand's slope limit. Some brands publish a second, lower slope limit for the edge of the lawn. The edge is the boundary line the mower follows and turns at. The main slope limit is for the middle of the lawn. For example, ECOVACS rates the GOAT O1000 RTK for a 45% slope in the middle of the lawn. Along the boundary, its limit is a 17% slope. Our yard finder checks that edge limit too. The finder works out one slope figure for your whole lawn. It compares that figure with the edge limit as well. Again, we take 15% off the brand's figure first. If your slope comes close to a mower's edge limit or goes over it, the finder ranks that mower lower. The mower then usually drops out of the three picks the finder shows you. Many brands give no edge limit. Then the finder says nothing about the edge. A missing edge limit does not mean the mower can handle the slope at your lawn's edge. Check the manual, and measure the slope along your lawn's edge.
Tree cover. Most wire-free mowers work out where they are from satellites. Branches, eaves and tall walls block that signal. If the mower cannot tell where it is, it drives off course, leaves strips uncut, and stops. A few also carry lidar. That is a spinning laser, and it measures what sits around the mower. Mowers with lidar keep working under trees. Trees rule out more mowers than any other feature of a lawn, so we check trees first.
What else we look at
- Getting between lawns. A front lawn and a back lawn are two separate areas for the mower to cover. Some mowers remember only one lawn, so you have to carry them to the other one. Some cannot fit down a side passage at all.
- How the mower handles things in its way. Cheap mowers use a bumper. They drive into things and turn. Better mowers use a camera or lidar. They see a hose, a toy or a pet, and drive around it.
- Cut height. Grasses grown in hot states grow best when you cut them tall. Clemson University lists the right cutting height for each grass. Cut St. Augustine grass at 2.5 to 4 in. Plenty of mowers will not cut that high. If you like your grass short, check a mower goes low enough.
- Noise. Owners complain about noise more than anything else once the mower has run for a few months. Makers state loudness in decibels. Add 10 decibels and a mower sounds about twice as loud. So a 70-decibel mower is a lot louder under a bedroom window than a 60-decibel one.
- What you install. Some mowers need a wire buried around the edge of the lawn to tell them where to stop. That wire is cheap and reliable. It takes a day to put in. And you have to repair it if you ever cut through it while digging. Some mowers use a small antenna on a pole instead. It needs a spot with a clear view of the sky and an outlet nearby.
- Running costs. Some mowers use a cell connection. It is free for the first year or two, then you pay monthly. We say which mowers charge, and from when.
How the star rating works
Scores are out of five and they are our own opinion. They are not an average of customer reviews, and no brand can change a score.
We give low scores as well as high ones. An average mower gets a score of about three. A score says how well a mower does the job on the kind of lawn that article is about. Each verdict names that lawn. If your lawn is a different kind, a high score may not apply to you.
What the yard finder can and cannot see
The finder reads your lawn from satellite photos and public ground-height data. Then it compares your numbers with the numbers each brand publishes, with a margin taken off first. It is a rough check. Nobody has measured your yard in person, and nobody has driven these mowers on your lawn.
How we make money
Every buy button sends you to Amazon with a code that tells Amazon you came from us. As an Amazon Associate we earn from qualifying purchases. It costs you nothing extra.
No maker pays for a place in a shortlist. We do not change a score because one mower pays us more commission than another. When a cheaper mower suits your lawn, we recommend the cheaper mower.
Tell us if we get it wrong
Specs change and brands revise their own numbers. If something here is wrong or out of date, tell us which page and what is off, and we will fix it. Email hello@mowitrobot.com.