Robot mower slopes: how percentages differ from degrees

By the Gladeburn team

Sources awaiting check

A slope rating of 30% does not mean 30 degrees. Comparing the wrong units can turn a plausible mower shortlist into an unsuitable one.

To convert a rise and run of your own, use the

Lawn slope calculator (% and °)

Turn a rise and a distance, or a phone spirit-level reading in degrees, into slope % and °, find your steepest section, and check it against a mower's rated maximum.

Open the slope calculator

. The lawn slope survey sheet gives you a page to record each section.

Understand the calculation

Gradient in percent is vertical rise divided by horizontal run, multiplied by 100. A hypothetical rise of 0.3m over a horizontal distance of 1m gives a 30% gradient. Its angle is about 16.7 degrees, using the arctangent of 0.3.

The distance measured along the sloping surface is not the horizontal run. Keep that distinction clear when recording a measurement, and do not attempt measurements on unsafe terrain.

Measure where the mower must work

Identify the steepest relevant section rather than averaging the entire garden. Mark slopes near boundaries, drops and narrow turning areas separately.

Husqvarna UK: Robotic mower FAQ says slope capability varies by model. Ask for the exact specifications and installation requirements, including any different limit at a boundary. Treat the quoted capability as manufacturer-stated and verify it for the particular machine you are considering.

Consider conditions beyond the number

Ask the installer about the surface, obstacles, route and space for turning. A single gradient value cannot establish that a machine will work safely next to a pond, wall or drop.

Do not conduct a trial on hazardous ground simply because your calculation is below a brochure figure. Obtain a site assessment where the consequences of losing traction would be serious.

Keep a clear comparison

Put both units beside each model's claim: percent and degrees. Record where the figure came from and whether it describes the lawn interior or a boundary condition.

If the supplier cannot confirm the difficult part of your garden, leave that area outside the proposed automated mowing plan. A well-defined manual section is preferable to assuming an advertised maximum is a guarantee for your site.

Sources