How to Choose a Robot Mower by Lawn Size

Working area is the first specification on every robot mower product page, and the one most likely to be misread. It is not a promise about your particular garden — it is a calculation, made under conditions that may not match yours.

Measuring your lawn

You do not need anything precise. Pace out each grassed area in metres — a normal adult stride is close enough to a metre — and multiply length by width. Add the areas together.

Exclude everything the mower will not cut: beds, borders, paths, the patio, the driveway, the pond. Owners routinely overestimate their lawn by including these, then buy more mower than they need.

For an awkwardly shaped lawn, break it into rectangles and add them up. For a rough figure on a rectangular plot, an aerial view in an online map with a measuring tool will get you close.

What the advertised maximum actually assumes

A published maximum working area is derived from how much grass the mower can cut per hour, how long its battery lasts, how long it takes to recharge, and how many hours a day the manufacturer assumes it will run.

Those assumptions are usually generous. They tend to describe a mower running most of the day, on level ground, in dry conditions, with an uninterrupted path back to its base.

Real gardens reduce that number:

• Slopes consume more battery for the same area covered.
• Obstacles cost time — every tree, chair and trampoline means a detour.
• Awkward shapes mean more turning and less cutting.
• Long grass in spring takes longer than the manufacturer's neat test lawn.
• Rain interrupts models that shelter during it.
• Restricted hours — if you forbid mowing at night, or during your neighbours' quiet hours, the machine has fewer hours to work with.

The headroom rule

Because of all this, choose a mower rated above your measured lawn:

• A margin of around 20% is a reasonable minimum for a simple, mostly level lawn.
• Around 40–50% is safer for a garden with slopes, several trees or a complicated outline.
• Buying exactly at your lawn size leaves no slack, and spring is when you find that out.

If your lawn measures 800 m², a mower rated for 1,000 m² is a comfortable choice, and one rated for 800 m² is a marginal one.

Where the size brackets fall

Robot mowers cluster loosely into groups, and the jumps between them are where the price steps up:

• Small gardens (up to about 500 m²). The largest and most competitive category. Boundary-wire models are common and inexpensive here, and perfectly adequate for a simple rectangular lawn.
• Medium gardens (roughly 500–1,500 m²). The mainstream. Wire-free navigation becomes normal, and multi-zone support starts to matter.
• Large gardens (roughly 1,500–3,000 m²). Battery capacity, cutting width and charging strategy begin to dominate. Wide decks matter, because a mower that cuts a wider strip covers ground faster.
• Very large gardens (3,000 m² and above). A specialist category. Some owners run two mowers on separate zones rather than one very large machine, which can be cheaper and gives redundancy.

Two mowers instead of one

For a large property split into distinct areas, two mid-range mowers are worth considering against one large one. They cost about the same, cut simultaneously, avoid the problem of getting between zones, and if one fails you still have a mown lawn. The downside is two base stations and two sets of blades to look after.

What to check before you buy

• Have you measured the lawn, or estimated it?
• Have you excluded the beds, paths and patio?
• Does the mower's rating exceed your measurement by a comfortable margin?
• Is your garden sloped, wooded or complicated — meaning you should allow more?
• How many hours a day will you actually let it run?