If your lawn has a bank, a berm, or a drop toward the street, slope is probably the specification that decides which mowers you can consider. It is also easy to misread, for two reasons: the units are not what most people assume, and some manufacturers publish more than one slope rating for the same machine.
Percent, not degrees
Manufacturers rate slope in percent, and percent is defined as:
(vertical rise ÷ horizontal run) × 100
So a slope that climbs 1 foot over 4 feet of horizontal distance is 25%. Climbing 1 foot over 2 feet is 50%. A 45% slope is not 45 degrees — it works out closer to 24 degrees, which is why the percent figure sounds more dramatic than the ground usually looks.
That difference is worth pinning down, because forums and video titles usually talk in degrees while every manufacturer we track rates in percent. The two scales only meet at one place — 100% is 45 degrees — and below that they pull apart quickly:
| Published rating | Roughly, in degrees |
|---|---|
| 10% | 6° |
| 15% | 9° |
| 20% | 11° |
| 25% | 14° |
| 30% | 17° |
| 40% | 22° |
| 45% | 24° |
| 50% | 27° |
| 70% | 35° |
| 80% | 39° |
| 100% | 45° |
So a mower advertised as handling a 45-degree slope is claiming something far steeper than one rated at 45%, and a “20 degree” figure quoted in a review is close to a 36% rating rather than a 20% one. When a number arrives in degrees, convert it before comparing it with anything on a spec sheet.
You can measure it in a couple of minutes with a straight board and a tape measure: rest the board on the slope, level it, then measure the gap between the downhill end and the ground. Divide that gap by the length of the board and multiply by 100. A 4-foot board with a 1-foot gap underneath is a 25% slope.
Interior and boundary ratings
Some manufacturers publish a single slope figure. Others publish two: one for the inside of the mowing area, and a separate, lower one for the boundary — the edge of the working area, where the mower tracks along the perimeter.
Where both are published, the gap can be large — in some cases the boundary rating is a fraction of the headline figure. That matters because a slope running right up to the edge of the lawn, which is what a bank along a driveway or property line usually is, is governed by the boundary rating rather than the headline one.
The table below shows what each manufacturer currently publishes.
Slope ratings, as published by each manufacturer
| Model | Inside the lawn | At the boundary |
|---|---|---|
| Segway Navimow X450 | 84% | Not verified |
| Dreame A3 AWD Pro 5000 | 80% | Not verified |
| Mammotion LUBA 2 AWD 1000 | 80% | 45% |
| Mammotion LUBA 2 AWD 10000 | 80% | 45% |
| Mammotion LUBA 2 AWD 3000 | 80% | 45% |
| Mammotion LUBA 2 AWD 5000 | 80% | 45% |
| Husqvarna Automower 435 iQ AWD | 70% | 50% |
| Husqvarna Automower 435X AWD | 70% | 50% |
| Yarbo Lawn Mower Module | 70% | Not verified |
| Segway Navimow X330 | 50% | 25% |
| Segway Navimow X350 | 50% | 25% |
| Segway Navimow X390 | 50% | 25% |
| ANTHBOT Genie 1000 | 45% Marketing claim | Not verified |
| ANTHBOT Genie 3000 | 45% Marketing claim | Not verified |
| ANTHBOT Genie 600 | 45% Marketing claim | Not verified |
| Husqvarna Automower 410 iQ | 45% | 15% |
| Husqvarna Automower 420 iQ | 45% | 15% |
| Husqvarna Automower 440 iQ | 45% | 15% |
| Husqvarna Automower 450X EPOS | 45% | 15% |
| Husqvarna Automower 415X | 40% | 15% |
| Kress KR173 | 40% | Not verified |
| Segway Navimow i105 | 30% | 10% |
| Segway Navimow i110 | 30% | 10% |
Figures come from each manufacturer's own published material. Follow a model link for the exact source and the date it was last checked.
Two things to notice in that table.
Not every manufacturer publishes a boundary figure. 16 of the 23 models we track publish a separate boundary slope rating. A blank does not mean the mower performs badly at the edge of a slope. It means the manufacturer has not published a figure, and it is worth asking the seller directly — particularly if your slope reaches the perimeter.
Some figures are marketing, not specification. Where a brand states a slope number in its sales copy but not in a specification table, we label it as such. Those figures are worth knowing, but they are held to a lower standard of evidence, and our selector will not use them to include or exclude a mower.
What a published rating does not describe
A slope rating is a single number, and there are several real-world conditions that a single number cannot fully describe. Unless a manufacturer documents them specifically, the published figure does not tell you how a machine behaves when:
- The grass is wet. Traction on wet grass is not the same as on dry grass, and published ratings generally do not state which condition they refer to.
- The mower crosses a slope rather than climbing it. Traversing and climbing are different demands, and a single figure does not distinguish between them unless the manufacturer says so.
- The ground changes angle abruptly. A sharp transition at the top or bottom of a bank is a different problem from the gradient itself, and is rarely covered by a slope specification.
We are not going to fill those gaps with estimates. If your measured slope is close to a model’s published limit, treat the specification as the start of a conversation: check the manufacturer’s own installation guidance and confirm the details with the seller before you buy.
Practical advice
If you have already measured the slope where your lawn ends and just want the shortlist, see robot mowers for a sloped boundary.
Measure the steepest part of your lawn, then measure the slope where the lawn ends — those are often different numbers, and the second is the one that gets overlooked.
Then put both into the mower selector. It rules out any mower whose verified rating falls short of what you entered, tells you which models could not be checked because the figure is not published, and names the specific constraint that ruled each one out.
If you already have two or three models in mind, the comparison tool puts their slope ratings side by side along with everything else each manufacturer publishes.