Up to the figure the maker states, in dry conditions, on turf that is already in good order. The number is real, and the conditions behind it are the part that is missing.
What the figure is
A maximum gradient, given as a percentage, obtained by the manufacturer on its own test surface. It is not a declared characteristic under any standard on this shelf, and no uncertainty accompanies it.
What it is measuring is traction, and traction on grass is wet-dependent. The same slope that a machine climbs in July is a slope it slips on in April, and slipping is worse than failing to climb: a driven wheel spinning on damp turf takes the surface off.
What actually decides it
The wheel. Deep-lugged drive wheels, or the spiked and studded wheels some makers offer as an accessory, make a larger difference than any other single factor.
Weight and where it sits. A machine with its mass over the driven axle climbs; one with it forward does not.
Where the slope is. A gentle bank in the middle of a lawn is easy. A slope that runs right up to the boundary is hard, because the machine has to turn on it, and turning on a gradient is where traction is lost. The same is true of a slope next to a hard edge or a drop.
Whether the machine has to cross it repeatedly. A robot mows constantly, so a marginal slope is attempted hundreds of times a season rather than once.
What to do with a slope the machine cannot manage
Fence it out of the loop, or draw it out of the map, and cut it with something else. A robot that is fighting a bank all summer is a robot wearing out drive parts and leaving tracks.
How this site handles it
The robot pages here print the slope figure with its unit exactly as the maker gives it, and state where the maker specifies the conditions. Where an accessory wheel set exists for a machine, the page says so, because on a sloping garden it is frequently the thing that makes the installation work.
The questions that keep coming in
Is the slope figure a percentage or degrees?
Almost always a percentage, and the two are very different numbers — 45 per cent is around 24 degrees. Where a listing gives a bare number with no unit, this site prints it as given and says the unit is unstated.
Why does my robot manage the slope in July and not in April?
Traction on grass is a wet-weather problem. A wheel that grips dry turf spins on the same slope after rain, and a machine that spins tears the surface it is standing on.
Last reviewed 26 September 2026