How Much Lawn Can a Robot Mower Really Handle?

Every robot mower advertises a maximum working area. It is the number buyers compare first, and it is the number most likely to mislead — not because manufacturers are dishonest, but because a laboratory calculation and a real garden are different things.

Where the number comes from

A maximum working area is essentially:

cutting rate × hours available per day × days between full cuts

The cutting rate depends on cutting width and driving speed. The hours available depend on battery life, charging time, and how many hours a day the mower is assumed to run.

Every one of those inputs is measured under favourable conditions: a level, rectangular, unobstructed test lawn, dry grass of moderate length, and a machine allowed to run for most of the day.

What real gardens subtract

Slopes. Climbing costs far more energy than level cutting. A sloped lawn reduces effective capacity noticeably.

Obstacles. Every tree, bench, trampoline and washing line is a detour. A garden with many obstacles takes considerably longer than an empty one of the same area.

Shape. A long thin lawn, or one with several narrow arms, means more turning and less cutting. Rectangles are efficient; complicated outlines are not.

Travel time. Time spent driving from the base station to a far corner, or between zones, is time not spent cutting.

Spring growth. In the peak weeks of spring, grass grows faster than the rest of the year combined. A mower sized for the average will fall behind in May.

Rain. Models that shelter during rain lose those hours entirely. In a wet climate this is significant.

Restricted hours. Most people do not let a mower run at night, and many restrict it further to avoid disturbing neighbours. Halve the assumed running hours and you halve the effective area.

A realistic way to choose

Rather than treating the advertised figure as a target to hit exactly, discount it:

• Simple, level, rectangular lawn, generous running hours — the advertised figure is broadly achievable. Allow around 20% margin.
• Some slopes, some trees, an ordinary garden shape — allow around 40% margin.
• Steep, wooded, complicated, or restricted mowing hours — allow 50% or more.

So a 1,000 m² lawn in an ordinary garden points at a mower rated for roughly 1,400 m², not 1,000.

The signs you have undersized it

• The lawn looks fine in July but ragged in May.
• The mower runs virtually every available hour.
• It never seems to complete a full pass before starting again.
• Parts of the lawn are visibly longer than others.

If this is happening, the usual remedies are to extend the permitted mowing hours, raise the cutting height so less material is removed per pass, or reduce the mowing area.

What to check before you buy

• How many hours a day will you genuinely allow it to run?
• Does it shelter from rain, and how wet is your climate?
• How obstructed and how sloped is the lawn?
• Have you applied a margin appropriate to your garden, rather than buying at exactly your area?