Stated area, and the assumption you are buying

What the convention amounts to

Somewhere in the last two decades the garden trade settled on describing a machine by the size of lawn it suits. The figure appears in square metres, usually preceded by “up to” or “bis”, and it is printed more prominently than anything a standard requires.

No standards body defines it. There is no test, no operating condition, no reporting requirement and no uncertainty statement. Each manufacturer arrives at its own figure by its own arithmetic, and nothing obliges the arithmetic to be published or to be the same as anyone else’s.

What the figure is derived from differs by machine type, and knowing which derivation you are looking at is most of the value.

On a cordless mower it is usually a battery calculation: the pack’s energy divided by an assumed draw, multiplied by an assumed walking speed and the deck width. The assumed draw is short, dry grass at a mid height setting.

On a robot it is a duty-cycle calculation: the area the machine can cover per hour of cutting, multiplied by the hours the maker expects it to run in a week, with an allowance for the overlap that random or systematic navigation produces.

On a mains or petrol mower it is barely a calculation at all — it is a positioning statement about deck width and build, since the machine has no energy budget to run out of.

On a sprinkler, a seed or a fertiliser it is a coverage figure, and that one is at least physical: a mass or a volume spread over an area.

What it does not promise

It does not promise your lawn. Length, moisture, slope, thatch, obstacles and how often you cut all change what a machine achieves, and none of them is in the assumption.

It does not promise a comparison. Two figures from two makers were produced by two undisclosed methods. The difference between “400 m²” and “500 m²” on two listings tells you less than the difference between their deck widths, which are at least measurable.

It does not promise a limit. A machine will not stop at its stated area. A cordless mower will simply want a second pack or a second session, which is a fact about your afternoon rather than about the machine.

It does not degrade gracefully with grass length. The single largest error in these calculations is grass that has grown a week too long, and it does not cost ten per cent — it can halve the result.

The documents it sits next to

None, and that is the point of this page. The measurable properties of the same machine — cutting width, rated input, battery capacity, guaranteed sound power — each have a document, and each has a page here. The area figure has none.

Where a listing prints an area beside a standard designation, the two are not the same kind of claim, and nothing on the label distinguishes them.

Which shelves it reaches here

Every mower family, the robots, and the coverage figures on the sprinkler, seed and fertiliser shelves.

This site prints the figure, because a buyer looking at a listing will see it and is entitled to see it here too. It prints it as a manufacturer’s assumption, names the machine type’s usual derivation where that is known, and never uses it to rank two machines against each other. Where a page needs to say which machine suits a larger lawn, it says so from deck width, pack energy and drive — the things that were measured.