Measure before you buy

Every home robot is sold against a limit, and every maker calls that limit something different on its spec page. Here is how to get your own numbers first.

HomeRobotDataUpdated September 18, 2026

Before you compare any home robot, measure five things: your lawn in square feet and its steepest slope in percent, your pool's type and longest dimension, your lightest cat's weight rather than your heaviest, the tallest threshold and rug edge in millimetres, and the smallest window pane you want cleaned. Each of those maps onto a hard limit on a maker's spec page, and each maker uses a different label for it. Get the numbers, then read the spec page.

Lawn: get the area, then get the shape right
Slope: measure the steepest strip, in percent
What the mower spec page calls the limit
Pool: type, longest dimension, and what the wall is made of
Cats: weigh the lightest one, not the heaviest
Floors: thresholds and rug edges in millimetres
Windows: frame, smallest pane, and the rope
The list to take to the spec page

Lawn: get the area, then get the shape right

Robot mowers are sold by area, and the labels vary. Husqvarna calls it Lawn Size and puts the tolerance in the label itself, as plus or minus 20 percent. Worx calls it recommended lawn size. eufy calls it max mapping area. Mammotion calls it coverage. Greenworks calls it maximum mowing area. Segway Navimow prints the acreage in the model name.

Measure by walking the perimeter and breaking the grass into rectangles, then adding them up and deducting beds, paths, patio and pool. Round up, because Greenworks' own advice is to buy a unit with slightly more coverage than your mowable grass.

Then look at the shape, because one maker publishes what shape costs you. The Husqvarna Automower 410 iQ is listed at 0.5 acre, and the same spec table gives area capacity - systematic as 0.5 acre and area capacity - irregular as 0.25 acre. A lawn split into a front, a back and a side strip joined by narrow necks is the irregular case, and the machine is rated for half as much of it.

Lawn size	Square feet	Square metres	A maker figure at this size
1/8 acre	5,445	506	Segway Navimow i105, sold as 0.125 acre
1/5 acre	8,712	809	Worx Landroid Vision WR220: up to 1/5 acre (8,712 sq. ft.)
1/4 acre	10,890	1,012	Husqvarna 410 iQ, area capacity - irregular
1/2 acre	21,780	2,023	Husqvarna 410 iQ, Lawn Size (plus or minus 20%)
3/4 acre	32,670	3,035	Mammotion LUBA 3 AWD 3000, coverage 0.75 acre
1 acre	43,560	4,047	Worx Landroid Vision Cloud WR340, recommended lawn size 1 acre

An acre is 43,560 square feet. Makers quote area in acres, square feet or square metres, and sometimes in two of the three on the same page.

Slope: measure the steepest strip, in percent

Slope is where the percent and degree scales trip people up. Percent is the drop divided by the horizontal distance, times 100, so a 45 percent slope is 24 degrees, not 45. Most mower makers print both, which lets you check the conversion yourself: Navimow states 30% (17 degrees), Mammotion states 80% (38.6 degrees) and Ecovacs states up to 50% (27 degrees). eufy is the exception in this set and gives the E15's limit only as slopes of up to 18 degrees.

To measure with a level, lay a straight board down the steepest line, lift the downhill end until a spirit level reads flat, and measure the gap between that end and the ground. Gap divided by board length, times 100, is the percent. To measure with a phone, the iPhone Measure app has a Level, which Apple describes as a way to determine how many degrees an object varies from level, with approximate measurements.

Measure at the edge of the lawn as well as in the middle. Husqvarna publishes two slope figures for the same machine: the Automower 410 iQ is rated maximum slope performance inside installation 45 percent, and maximum slope performance at boundary 15 percent. The 435X AWD is 70 percent inside and 50 at the boundary. A bank running up to the fence line is judged against the smaller number.

Degrees	Percent	Where that lands
5	9	A barely noticeable fall across a flat lawn
10	18	Comfortably inside every mower in our set
17	31	Navimow i105 and Worx WR340 both stop here, quoted as 30% (17 degrees)
18	32	eufy E15's stated ceiling, published in degrees only
24	45	Navimow i2 AWD, quoted as 45% (24 degrees)
27	50	Ecovacs GOAT, quoted as up to 50% (27 degrees)
35	70	Husqvarna 435X AWD, inside the lawn
39	80	Greenworks AiMowbot at 80% (39 degrees); Mammotion LUBA 3 AWD at 80% (38.6 degrees)

Percent is rise over run times 100. The two scales cross at 45 degrees, which is 100 percent. Figures in the right-hand column are the makers' own.

What the mower spec page calls the limit

The same two numbers hide behind six different labels. If you are comparing two mowers and one seems to have no slope figure, you are almost certainly reading the wrong row.

Husqvarna is the most informative and the most work to read, because one model carries four separate area and slope entries. Everyone else gives you one of each, and two of them bury the slope figure in a marketing headline rather than the spec table.

Note the Navimow row in particular. Mowing area per charge is not the lawn the mower will keep cut; it is how much it covers between trips to the dock, and it is a much smaller number.

Maker	Area limit is called	Slope limit is called
Husqvarna	Lawn Size (plus or minus 20%), plus area capacity - systematic and area capacity - irregular	Maximum slope performance inside installation, and maximum slope performance at boundary
Segway Navimow	Acreage in the product name; mowing area per charge is a separate, smaller figure	Slope climbing working capability, percent with degrees
Mammotion	Coverage	Stated in the headline, percent with degrees
Worx	Recommended lawn size	Slope handling, percent with degrees
eufy	Max mapping area	Handles slopes of up to, in degrees only
Greenworks	Maximum mowing area	Slope capability, percent with degrees

Watch the Navimow row. Mowing area per charge is not the lawn the mower will keep cut; it is how much it does between trips to the dock.

Pool: type, longest dimension, and what the wall is made of

Three numbers decide a pool robot, and pool type is the one that excludes rather than degrades. Maytronics labels it Pool Classification and fills it with In Ground, Above Ground, or In ground and Above Ground. Aiper labels it ideal pool type; Wybot labels it supported pool types; Hayward labels it pool type. Hayward's R110 page shows why the label is not enough on its own: the spec table lists both pool types, while the question-and-answer block on the same page says the cleaner is designed for use in inground pools only, and may cause damage to an above ground pool.

Size is published two ways. Maytronics uses maximum pool length in feet, giving 40 ft for the Nautilus CC Plus with Wi-Fi and 50 ft for the Explorer E50. Wybot uses area, listing the C1 for pools up to 1,615 sq. ft. Measure your longest run and your surface area, because you will meet both. Wall material is the check almost nobody makes: Aiper lists applicable pool material as concrete, fibreglass, vinyl and tiles.

For an above-ground pool, read the wall-climbing row rather than the marketing. Maytronics calls it cleaning coverage, and its above-ground models, the Nautilus AG and the Escape, both read Floor, while the in-ground Nautilus Titan reads Floor, Walls and Waterline. The corner matters too: Hayward's own answer on the SharkVac XL page says that with no radius to the transition from floor to wall, most all cleaners will have difficulty climbing the walls.

Maker	Pool type	Size limit	Wall and waterline
Maytronics (Dolphin)	Pool Classification	Maximum Pool length, in feet	Cleaning Coverage
Aiper	Ideal Pool Type	Pool Size, in square feet and length	Wall Climbing Ability, as an angle
Wybot	Supported Pool Types	Ideal Pool Smaller Than Size, in square feet	Wall-Climbing and Waterline Cleaning
Hayward	Pool Type	Not published per model	Described in prose, not as a spec row
Bestway	Recommended for flat-bottom above ground pools	Total area, in square feet	Not claimed

Maytronics quotes length, Wybot and Bestway quote area, Aiper quotes both. Measure your pool once, in both.

Cats: weigh the lightest one, not the heaviest

Every buyer checks whether the box fits the big cat. The limit that causes trouble is the minimum, because the machine has to detect the cat to protect it. Whisker describes the mechanism plainly: the unit uses laser and weight sensor technology to detect when your cat enters and exits the globe, which then triggers the countdown timer and cleaning cycle. If the cat is too light, the sensor may not register it at all.

The makers spell out the consequence. Litter-Robot's page for the 3 Connect says kittens and small cats that weigh less than 5 pounds may not be heavy enough to trigger the cat sensor. Whisker's acclimation guide sets both thresholds side by side: your cat needs to weigh at least 3 pounds for Litter-Robot 4 and 5 pounds for Litter-Robot 3 to use automatic mode. If you have a kitten, a senior cat that has lost weight, or a small breed, that is the number to write down.

Weigh every cat, take the lightest and the heaviest, and check both ends against the same spec row.

Model	What the spec is called	Stated range
Litter-Robot 4	Suitable for cats that weigh	3 to 25 lbs
Litter-Robot EVO	Suitable for cats that weigh	3 to 19 lbs
Litter-Robot 3 Connect	Must weigh at least X to trigger the cat sensor	5 lbs and up, no stated maximum
PETKIT Purobot Max 3	Cat Weight Limit	3.3 to 22 lbs
Neakasa M1	Cat Weight Limit	2.2 to around 33 lbs
Petlibro Luma	Best for adult cats over X and under Y	2.2 to 22 lbs

PETKIT also states an age floor alongside the weight range for the Purobot Max 3: cats 6 months and older.

Floors: thresholds and rug edges in millimetres

Measure the tallest threshold in the house in millimetres, and the lip of every rug the robot will meet. The spec you are matching it against is called four different things. Roborock calls it maximum double-layer threshold crossing and rates the Saros 10R and Qrevo Curv at 1.57 inches, or 4 cm. Ecovacs calls it barrier crossing ability (mm) with mop and rates the Deebot X8 Pro Omni at 20. eufy calls it obstacle clearance height and rates the X10 Pro Omni at 21 mm. iRobot states 3.5 cm threshold climbing for the Roomba Max 875 Combo, and eufy's support page for the Omni X12 Pro caps it at 2 cm and tells owners to use a threshold auxiliary strip above that.

Carpet has two limits of its own. Mop lifting keeps a wet pad off the wool, and Roborock calls it maximum mop lifting, at 22 mm on the Saros 10R and 17 mm on the Qrevo Curv, while Ecovacs calls it automatic mop lifting (mm), at 10 on the X8 Pro Omni. Pile depth is the other: Ecovacs' Deebot X8 family manual says not to use the robot on shaggy rugs or carpets with fibres longer than 10 mm, and eufy says that for carpets with fibers longer than 26 mm, the Omni X12 Pro may struggle to clean.

Rug edges stop more robots than thresholds do. Ecovacs' manual tells owners to tuck rug fringe under the rug base, and separately to fold the rug and tuck the tassels under. eufy's guidance is to secure all four corners with tape so the rug lies flat. Measure the lip with the tape already in place.

Maker	Threshold spec is called	Mop-lift spec is called
Roborock	Maximum double-layer thresholds / max. double-layer threshold crossing	Maximum mop lifting
Ecovacs	Barrier crossing ability (mm) (with mop), or obstacle crossing	Automatic mop lifting (mm)
eufy	Obstacle clearance height	Stated as raising the mops by a height in mm
iRobot	Threshold climbing	DriLift Technology, no height published
Dreame	ProLeap or EasyLeap, stated as obstacles crossed	Mop lift

Two-layer thresholds, where a strip sits on top of a sill, are what Roborock's double-layer figure refers to. Measure the whole stack.

Windows: frame, smallest pane, and the rope

Window robots are the one category where the frame is a feature rather than an obstruction, and the makers split on it. Ecovacs lists applicable frame type for the WINBOT line as with frame and frameless, and its FAQ sets a tolerance rather than a rule: smooth glass free of decals, stickers and cracks, with obstacles under 4 mm or frames under 2 mm. HOBOT is narrower, saying the robot was designed only for rectangular window frames and that it does not recommend using it on rounded frames in any way.

Only the minimum pane size is published as a spec. Ecovacs uses min. window size (cm) and gives 30 by 40 for the WINBOT W2S and 22 by 25 for the WINBOT mini, and the W3 OMNI adds min. glass thickness (mm) at 3. HOBOT uses workable window size and states greater than 40 by 40 cm for the 2S and the 298. Maximum size exists only in marketing copy. Measure your smallest pane, because that is what rules a model out.

The last number matters only if the glass is above ground level. Ecovacs says the WINBOT includes a reinforced compound cable that acts as a safety rope, plus a backup battery system that can keep it attached for more than 30 minutes if the main battery runs low. HOBOT's FAQ says its battery is designed to hold the HOBOT for 20 minutes so that it does not fall in a power outage, and its instruction for the 388 is to always tie the safety rope to an indoor fixture.

Model	Frame type	Minimum pane	Holds on in a power cut
Ecovacs WINBOT W2S	With frame and frameless	Min. window size 30 x 40 cm	Over 30 minutes
Ecovacs WINBOT mini	With frame and frameless	Min. window size 22 x 25 cm	Over 30 minutes, with an alarm
Ecovacs WINBOT W3 OMNI	With frame and frameless	Min. glass thickness 3 mm	Over 30 minutes
HOBOT-2S and HOBOT-298	Rectangular frames only	Workable window size over 40 x 40 cm	20 minutes

No WINBOT or HOBOT page we read publishes a maximum window size as a labelled spec, only as marketing copy.

The list to take to the spec page

Write these down once, on paper, before you open a single product page. Every one maps to a row on a spec table, and every one can rule a machine out on its own.

Lawn: total mowable square feet, whether the lawn is one piece or several, and the steepest slope in percent, measured at the boundary as well as in the middle.
Pool: in-ground or above-ground, longest dimension in feet, surface area in square feet, and what the wall and floor are made of.
Cats: the lightest cat's weight and the heaviest cat's weight, both in pounds.
Floors: the tallest threshold in millimetres including any strip on top of it, the height of the worst rug lip, and the deepest carpet pile.
Windows: the smallest pane you want cleaned, in centimetres, whether the panes are framed or frameless, and whether any of them are above ground level.

Questions people ask

How many square feet is a quarter acre?

10,890 square feet, or about 1,012 square metres. An acre is 43,560 square feet, so the fractions are easy once you have that: an eighth is 5,445, a half is 21,780 and three quarters is 32,670. Mower makers quote all three units, sometimes on the same page, so convert before you compare.

Is a 45 percent slope the same as 45 degrees?

No. Percent is the drop divided by the horizontal run, times 100, and 45 percent works out at 24 degrees. The two scales only meet at 45 degrees, which is 100 percent. Several mower makers print both, such as Navimow's 30% (17 degrees) and Mammotion's 80% (38.6 degrees), which is the easiest way to sanity-check your own conversion.

Why does the minimum cat weight matter more than the maximum?

Because the safety system is a weight sensor. Whisker says the Litter-Robot uses laser and weight sensor technology to detect when your cat enters and exits the globe, and that is what triggers and pauses the cycle. Litter-Robot's own page for the 3 Connect says kittens and small cats under 5 pounds may not be heavy enough to trigger the cat sensor. Weigh the smallest cat in the house.

How do I measure a threshold for a robot vacuum?

In millimetres, from the floor to the highest point the robot has to cross, including any transition strip sitting on top of a sill. That stack is what Roborock means by a double-layer threshold. Then compare it to the maker's own row, which is called barrier crossing ability by Ecovacs, obstacle clearance height by eufy and threshold climbing by iRobot.

Will a wall-climbing pool cleaner work in my above-ground pool?

Usually not, and the spec row will tell you before the marketing does. Maytronics uses the cleaning coverage field, and its above-ground models, the Nautilus AG and the Escape, both read Floor, while its in-ground Nautilus Titan reads Floor, Walls and Waterline. Wybot's A1 says outright that it is for pool types with a flat bottom and floor only.

Do I need to measure my windows if the robot says frameless is fine?

Yes, because the published limit is the minimum, not the maximum. Ecovacs states min. window size of 30 by 40 cm for the WINBOT W2S and 22 by 25 cm for the WINBOT mini, and HOBOT states a workable window size of over 40 by 40 cm. Small bathroom and stairwell panes are what these figures rule out.