Robot Mower Size and Capacity Guide

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What a coverage rating actually measures

Robot mower coverage is quoted as the working area the machine can maintain in a day of repeated cycles, not the area it cuts in one outing. European listings state it in square metres, North American ones often in acres, and an acre is just over four thousand square metres, so a machine rated for half an acre is being asked to keep roughly two thousand square metres in order. A small garden is quoted in the hundreds of square metres. The rating is a ceiling measured on open, uncluttered turf with the dock inside the lawn, so the number to compare against is your measured grass area, not the area of the plot. Landscaped beds, paths, a driveway and the footprint of the house do not count, but every patch of grass does.

Area per hour, cutting width and passes

Underneath the daily rating is a rate: the area a machine covers per hour, which is roughly cutting width multiplied by ground speed, reduced by the overlap the guidance system needs and by every turn. Cutting decks range from narrow discs around sixteen centimetres across on small machines to bars over thirty centimetres on larger ones. A narrow deck still reaches the same daily total if the battery and schedule allow, because the mower simply makes more passes, but the same strip gets driven over more often, which matters on soft or shaded turf. Navigation style changes the effective rate as much as deck size does: an erratic, bounce-and-turn pattern covers some ground twice, while a guided back-and-forth path keeps overlap tighter.

Runtime, charge time and cycles per day

Daily output comes from the duty cycle, not the size of one battery. A machine that runs for an hour and recharges in an hour delivers roughly half of every working day to the blade, and the real number is lower once you subtract the trip from the far zone back to the dock and the time parked while waiting for its next slot. A larger pack stretches each run, which suits large lawns or far zones, but it does not shorten the recharge unless the charger is also more powerful. That is why two mowers with the same daily rating can be very different in practice: one may spend the day on the lawn in long runs, the other may shuttle to the dock constantly, and a dock placed at the far end of the garden wastes part of every cycle. During hot weather, or when the machine charges in a garage, ambient temperature also affects how quickly the pack accepts charge.

Complexity multipliers: obstacles, zones and corridors

Two gardens of identical size are not equal work. Each tree, bed island, shrub, play set and bird bath forces a detour and a slow-down, and a garden scattered with them can take far longer per square metre than an empty field. Zones connected by a corridor add travel time and require guide wires or manual carrying, and every zone needs its own scheduled slot so the machine is not spread too thin. Slopes and narrow strips also cut the effective rate, because a mower slows on a bank and cannot make long runs in a strip narrower than two passes. When comparing a rating with a garden, count the islands, the number of zones and the length of the thinnest strip, then choose a machine with headroom rather than one that matches on paper.

Slope limits in degrees and percent

Slope is quoted either in degrees or as a grade, the ratio of rise to run, where a forty-five degree slope is a hundred percent grade and a modest-looking thirty percent grade is about seventeen degrees. Manufacturers usually publish a maximum climbing angle separately from a maximum lateral angle, and the surviving figure is the smaller of the two, because a mower that can climb a bank may still slide sideways across it. Traction, not power, is normally the limit: wheel diameter, tread pattern, grass moisture and the weight over the driven wheels all decide whether the machine keeps its grip. Measure the steepest part of the garden rather than eyeballing it, treat the published figure as a dry-turf maximum, and plan a physical barrier at any drop a sliding mower could reach.

Measuring the real lawn area

Break the garden into simple shapes and measure each one, or use a satellite measuring tool and then verify the total with a tape along the longest and widest runs. Subtract everything that is not grass: beds, paving, the house footprint, paths, a pond and a vegetable patch. The result is the working area the coverage rating must beat, and it is almost always smaller than the plot size quoted in a listing. While you are out there, measure the perimeter as well, since the boundary wire has to travel it with slack at corners, and note the width of the narrowest passage and the length of the longest strip. A phone level or a straight edge and a spirit level will give you a usable slope reading; note the steepest section and its direction.

Matching capacity to how often you want it out

The daily rating also sets how much of the day the machine will be working. A mower sized to the area it services runs a short session and spends most of the day docked, which keeps noise, wear and battery cycles low and leaves the lawn tidy between runs. A machine running at its limit works almost continuously, and any interruption — rain, a fault, a flat battery — shows up immediately as uncut strips. If the garden is close to a rating boundary, or if you want the mower out of the way by evening, step up a class. The exception is a lawn left deliberately long in summer, where more frequent short runs with a higher deck beat fewer long ones.

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FAQ

Is a machine rated for a thousand square metres enough for my garden?

Only if your measured grass area is comfortably below it. The rating assumes open turf, no zones, and a full day of cycles. Subtract beds and paving, count the obstacles and corridors, and pick a class with headroom if you want the lawn finished each day rather than most days.

How many acres is five thousand square metres?

Just over one and a quarter acres, since an acre is about four thousand square metres. Going the other way, half an acre is roughly two thousand square metres. Convert before comparing listings, because a rating in acres and a measurement in square metres are easy to misread against each other.

Does a wider cutting deck always mean faster mowing?

Not by itself. Rate depends on width, ground speed, overlap and turns, so a wide deck on a slow machine can be matched by a narrower one that travels faster and repeats fewer passes. On small, cluttered lawns the wider deck can even be a disadvantage, because it cannot turn as tightly.

Can a robot mower handle a steep bank?

Only up to the slope limit the manufacturer publishes, and that figure assumes dry, firm ground with grip available. Climbing ability is usually better than lateral stability, so crossing a bank sideways is the riskier manoeuvre. Wet grass reduces traction, so leave margin rather than operating at the limit.