Slope Guide
That HillChangesEverything.
Slope is the single most misunderstood spec in robotic mowing. Here's why it matters, how to read it, and what your hill really demands of a mower.
Degrees vs. percent grade
Mower spec sheets quote slope in one of two units: degrees (°) or percent grade (%). They are not interchangeable. A 20° slope is roughly 36% grade. A 30° slope is about 58% grade. A mower rated for 20° will not hold a 30° hill — even though both numbers sound modest.
Before you buy, convert the spec to the same unit your yard's slope is measured in. Most phone leveling apps can read both. Match the unit, then compare.
Patch's Note
42% slope and 42 degrees aren't the same thing. 42° ≈ 90% grade — nearly vertical. Always check the unit on every spec sheet.
Where traction comes from
Climbing is about grip and torque, not just power. AWD mowers drive all wheels and keep traction on slopes where a two-wheel-drive mower slips and spins. Larger drive wheels and aggressive tread also help.
If your yard has any section steeper than ~25°, an AWD mower is the safer bet. Below ~20°, most capable mowers hold fine — but check the actual rating, not the marketing copy.
Patch's Note
Measure your steepest section, not the average. The mower has to climb the worst part, not the easy part.
What to measure before you shop
Find your steepest mowable section — the one the mower has to climb, not the gentle average. Measure it in degrees and percent. Then add a margin: a mower rated exactly to your slope will struggle in wet grass. Buy headroom.
If you can't measure precisely, describe the hill in plain language to any retailer: 'walkable but steep', 'too steep to mow comfortably', 'almost too steep to stand on'. Honest descriptions beat guessed numbers.