How to choose a robot mower

The best robot mower for your neighbour may be the wrong one for you. What matters is your garden: how big the lawn is, how steep it gets, whether it's one lawn or several, how narrow the gaps between them are, and what's growing round it. Get those right and the shortlist almost writes itself.

The short answer

1. Measure the lawn in m², minus beds and patios.
2. Find the steepest slope the mower must climb, in % (brands quote %).
3. Count the zones and measure the narrowest passage between them.
4. Pick the navigation that suits your trees, buildings and edges.
5. Shortlist models rated above your lawn, with some headroom, and for your slope.

The chooser above does steps 4 and 5 from your answers.

A worked example

A 450 m² garden in two parts, joined by a 0.9 m side passage, with a 25% bank at the back and a couple of trees near the edge. The owner doesn't want to lay boundary wire.

• Navigation: with only a couple of trees, RTK is still workable; a hybrid or LiDAR model copes better with tree cover. A wire model is ruled out by choice, not by the garden.
• Area: look for a model rated for about 540 m² or more: the lawn plus our one-fifth headroom.
• Slope: the model must be rated for at least 25%. That's 14°, so don't be caught out by a spec in degrees.
• Zones and passage: it must support more than one zone, and its body must fit through 0.9 m with room to spare.

Step 1: measure your lawn

Rated area is the headline spec, so get your own number first. Split the lawn into rectangles, circles and triangles, add separate lawns as separate zones, and take away beds and patios. Our guide to measuring your lawn shows how, and the lawn area calculator does the sums.

Step 2: find the steepest slope

Measure the steepest part, not the average. Brands usually give max slope in %, and 100% is 45°, not vertical. The slope calculator converts both ways.

Step 3: zones and passages

If your lawn is in several parts, the mower needs to get between them, either by driving through a passage or by being carried. Check that the model supports multiple zones, and that its published width fits your narrowest gap.

Step 4: choose the navigation

• Boundary wire works almost anywhere, including under trees, but you lay a wire round every edge.
• RTK needs a clear view of the sky over most of the lawn.
• Camera vision needs clear, visible lawn edges.
• LiDAR maps fixed features round the garden, so it suits enclosed gardens.
• Hybrids combine two methods to cover each other's gaps.

Read wire vs RTK vs vision for the detail.

Step 5: compare rated specs, with headroom

Rated areas are usually for ideal conditions. Slopes, narrow strips, trees and several zones all slow a mower down. We suggest a model rated for at least a fifth more than your lawn: that's our rule of thumb, not a brand figure.

What to look for when you buy

We haven't tested these mowers; we compare published specs. These are the criteria we'd use, in order:

• rated area at least a fifth above your lawn
• rated max slope above your steepest section
• multi-zone support if you have more than one lawn
• a body narrower than your narrowest passage
• the navigation type that suits your garden
• then warranty, noise and any app subscription

FAQs

Is a bigger rated area always better?

Not beyond the headroom you need. A model rated far above your lawn usually costs more, and may be bulkier to fit through passages.

Do I need a garage for a robot mower?

No, most are built to live outside, but a cover keeps the worst of the weather and leaves off the dock. Our garage guide is coming soon.

Should I run it every day?

Little and often suits robot mowers, but always in daylight. Our schedule tool, coming soon, works out a daylight-only window for your lawn.