For a large yard — roughly 20,000 square feet up to three quarters of an acre — the best lawn mower is the Greenworks 80V 21" Self-Propelled. At that size deck width has stopped being the constraint and endurance has taken over, and the 80V platform carries enough charge to finish a big lawn in one go while driving itself up the slope at the far end. For a medium yard in the 4,000–20,000 square foot band, the Greenworks 60V 21" twin-battery kit is the same 21-inch cut for less money, and the EGO LM2135SPis the premium answer if you want the best-built machine in the class. Under 4,000 square feet, stop reading and buy a narrow deck — the Greenworks 40V 17" is here for exactly that.
The reason a bigger yard wants a different mower is not strength, it is arithmetic. Deck width does not change how fast you walk. What it changes is how many lengths you have to walk, and that is simply your lawn’s width divided by the deck’s width. On a small lawn that division barely matters; on a big one it is the difference between forty minutes and an hour and a quarter, every week, for thirty weeks a year. Past about three quarters of an acre the division stops helping at all and you should change category entirely — see the best riding lawn mower.
A note on measuring, because it decides which of these picks is yours: people underestimate their lawns, consistently and by a lot. Pace out the length and the width of each section of grass, multiply, and add the sections together. A pace is close enough to three feet for this purpose. Do it before you shop — the single most common mower-buying mistake is sizing to a guess. We have not mown a large yard with any of these machines; the ranking reasons from published deck widths, drive type and battery platform, which is how we pick everything here.
The arithmetic, in one worked example
Take a rectangular lawn 60 feet wide and 80 feet long — 4,800 square feet, a thoroughly ordinary suburban back garden. With a 17-inch deck and a small overlap, you are cutting a usable 16 inches per pass, so 60 feet of width is 45 lengths. With a 21-inch deck cutting a usable 20 inches, the same lawn is 36 lengths. That is nine fewer lengths of 80 feet, which is 720 feet of walking saved — every cut, thirty times a year, for as long as you own the mower.
Run the same sum on a 2,500 square foot lawn and the saving is trivial, while the extra deck width makes every turn around the apple tree harder. That crossover, somewhere around 4,000 square feet for most lawn shapes, is exactly where our small-yard list stops being the right page and the best lawn mower starts.
What size lawn mower do you need? Deck width by lawn area
| Lawn area | Deck width | Drive / power | Our pick |
|---|
| Under 4,000 sq ft | 16–17 in | Push, single battery | Greenworks 40V 17" |
| 4,000–20,000 sq ft (medium yard) | 20–21 in | Self-propelled | Greenworks 60V 21" |
| 20,000 sq ft – 0.75 acre (large yard) | 21 in | Self-propelled, twin battery or gas | Greenworks 80V 21" |
| Over 0.75 acre | 42 in and up | Riding mower or zero-turn | See the riding roundup |
Under 4,000 sq ft — 16 to 17 inches.Turning beats coverage at this size. A narrow deck gets round beds in one pass, weighs less for steps and storage, and costs less. The Greenworks 40V 17" is our pick.
4,000 to 20,000 sq ft — 20 to 21 inches.The large majority of suburban lots. A 21-inch deck is the standard for good reason: it is the widest cut that still fits most gates and turns reasonably. The Greenworks 80V 21" Self-Propelled is the pick.
20,000 sq ft to 0.75 acre — 21 inches, two batteries or gas. Deck width is no longer the constraint; endurance is. Buy a twin-battery kit like the Greenworks 60V, or accept gas. Anything less and you will stop halfway.
Over 0.75 acre — not a walk-behind. At this point the honest advice is to change category. An hour and a half behind a 21-inch deck every week is not a mower problem you can solve with a bigger mower; see the best riding lawn mower, best zero-turn mower and zero-turns for two acres.
The two overrides
The gate. Measure the narrowest point between where the mower is stored and where the grass is. A 21-inch mower needs roughly 24 inches of clear opening; a 17-inch mower roughly 20. A deck that will not reach the lawn is worth nothing, and this measurement beats every other consideration on this page.
The slope.Lawn area tells you deck width. Gradient tells you drive type. Any meaningful slope and you want self-propelled, ideally rear-wheel drive, at whatever deck width your area calls for — the reasoning is in our self-propelled roundup. On a severe side slope, a lawn tractor is safer than either a zero-turn or a walk-behind.
What about cutting height?
Not strictly a sizing question, but it is the spec that will do most for your lawn, so check it while you are comparing. More height positions means you can cut low in spring and raise the deck through summer heat, which shades the soil and crowds out weed seedlings. A lawn mown too short in July is the usual reason people go looking for fertilizer and seed in August.
