Robot mowers for slopes and hills: what the ratings mean

Most wire-free robot mowers handle a gentle slope without trouble. Of the 87 models on sale in the four countries we cover, 76 are rated for at least 45% (about 24°). For steep lawns the list gets much shorter. Only 33 models are rated for 70% or more, and all 33 of them have all-wheel drive. The steepest two-wheel-drive rating we have is 60%. Where the slope sits on your lawn, and how wet the grass is when the mower runs, matter about as much as the rating.

Percent and degrees are not the same number

Makers quote slopes in percent, sometimes with degrees in parentheses. Percent is the rise divided by the level distance, times 100. In Husqvarna's example a lawn climbs 15 cm over one meter, so 15%. Degrees describe the angle itself, and that number is always the smaller of the two (the gap grows the steeper it gets).

• 25% is about 14°
• 45% is about 24°
• 70% is about 35°
• 100% is exactly 45°

So a mower "rated for 45%" climbs a slope of about 24°. Product pages sometimes get the conversion wrong. One Eufy page lists the E15 as "less than 40% (18 degrees)", while 18° works out to about 32%.

How to measure your own slope

Navimow's own guide describes a string method that needs nothing more than what's in most sheds. One stake goes in at the top of the slope and one further down, with a string tied between them and pulled level. How high the string hangs above the ground at the lower stake, divided by the distance between the stakes, gives you the slope, so a foot of rise over ten feet is 10%. If that sounds like too much work, a free incline app on your phone, laid on a straight board, gets you close enough.

Measure the steepest part your mower will actually drive on, not the average across the lawn. Then measure again right next to the border, fence or flower bed, because that is where most mowers give up first.

The edge of a slope is the hard part

A mower driving straight up a slope is doing what the rating describes. At the boundary it has to turn, often across the slope, and that is when the downhill wheels slide. Husqvarna and Navimow both publish a separate, lower figure for slopes along the boundary. The Navimow H2, for example, is rated for 45% in the work area and 25% along the boundary.

Only 34 of the 87 models on sale have a published edge figure. For the two-wheel-drive models among them, the edge figure is 33% to 67% of the main rating. All-wheel-drive models hold up much better, and several Navimow AWD models keep their full rating right to the edge.

Figures from manufacturer specs as of Oct 26, 2026.

If a maker doesn't publish an edge figure, the fit check assumes about a third of the main rating for two-wheel drive and half for all-wheel drive. That estimate can't rule a mower out on its own. It shows as "check first", so you know to ask.

Ratings assume good conditions

Ratings are measured in good conditions. Navimow's footnote for the i2 AWD says the 45% figure was reached on dry grass about 2 inches long, with nothing in the way. Husqvarna's manuals call the slope values approximate and note that they assume a correctly calibrated tilt sensor. On wet grass a mower loses grip much sooner. Husqvarna warns that rain increases the risk of slipping on steep slopes, and Mammotion and Eufy say much the same about traction on wet lawns.

That's why the check calls a slope a clear fit only up to 75% of the rating, and a tight fit between that and the rating itself. A mower working at its limit every day spins its wheels more and leaves ruts in the turf.

Mowers rated for 70% or more

If your slope is over about 50% (27°), start here, because a 70% rating still gives a clear fit up to about 52%. Check the edge column too, and the countries, because several of these are sold in one or two markets only.

Figures from manufacturer specs as of Oct 26, 2026. A dash means the maker doesn't publish it.

Making a steep lawn easier for any mower

A few changes to the lawn itself help any mower. Navimow suggests leveling the slope surface, which in practice means filling the bumps and holes where a wheel can lose contact. Husqvarna recommends at least 50 cm (1.6 ft) of level ground between a flat area and a steep slope for its AWD models, and putting the boundary on flat ground before the slope starts, so the mower turns where it has grip. Keep the wheels clean as well. Husqvarna points out that wheels clogged with grass make slopes much harder.

Sometimes the steep bit is one corner by the fence. Leaving that corner out of the map, and doing it by hand a few times a summer, can save you from paying for all-wheel drive across the whole lawn. Run the fit check twice, with and without the corner's slope, and see how much the list changes.

Common questions

What is the steepest slope a robot mower can handle?

The highest rating among the wire-free models sold in the US, Canada, the UK and Australia is 100% (45°), for the Lymow One Plus 5A. 43 of the 87 models are rated between 45% and 60%. Every model rated for 70% or more has all-wheel drive.

Is a 45% slope the same as 45 degrees?

No. A 45% slope rises 45 cm over 1 m of level distance, which is about 24°. A 45° slope is 100%: it rises as much as it runs. Only the Lymow One Plus 5A and Lymow One Plus 10A are rated that high.

Can a robot mower go up a hill when the grass is wet?

It will try, but it loses grip much sooner than on dry grass. The rating on the box is measured on dry grass. Navimow suggests waiting at least 24 hours after heavy rain before mowing a steep slope, and many mowers have a rain sensor or a rain delay you can switch on.