Guides
What size mower do I need for my yard?
Deck width sets how long you spend. Watt-hours set whether you finish. Here are both, by lawn size.
Affiliate disclosure: we earn a commission if you buy through our links, at no extra cost to you. It never changes which product we rank first — here is how we're funded.
We have not tested these units. Every spec on this page comes from the manufacturer's own documentation and is linked to it. Every computed figure is arithmetic you can redo. Prices are checked daily — last verified January 1, 1970. Here is exactly how we pick.
The sizing table
| Lawn size | Deck | Mowing time | Watt-hours needed | Type |
|---|---|---|---|---|
| Up to 1/4 acre (10,890 sq ft) | 20 in | ~25-35 min | ~140Wh | Push |
| 1/4 to 1/3 acre | 20-21 in | ~35-45 min | ~270Wh | Push or self-propelled |
| 1/3 to 1/2 acre (21,780 sq ft) | 21 in | ~50-70 min | ~450-600Wh | Self-propelled |
| 1/2 to 1 acre (43,560 sq ft) | 21 in, two packs | ~70-110 min | ~600-1,000Wh | Self-propelled, dual battery |
| 1 to 2 acres | 42 in | Seated, a fraction of the time | ~1,120Wh per acre | Riding / zero turn |
| Over 2 acres | 42 in, 6 packs | Seated | ~1,120Wh per acre | Riding, extra batteries |
Times assume walking pace with realistic overlap; watt-hour figures use ~4Wh/min for a 20 in push deck, ~7.5Wh/min for a 21 in self-propelled and 1,120Wh per acre for a 42 in riding deck. All three per-minute rates are derived from manufacturer runtime claims, shown below.
Where those numbers come from
Real mowing is slower than that because of turns, trimming around obstacles and emptying a bag, and faster in places because you are not walking a perfect grid. Treat the outputs as a range rather than a stopwatch.
The second number nobody gives you
Deck width tells you how long the job takes. It does not tell you whether the mower can finish it, and that is a separate calculation.
Multiply your mowing time by the right rate, add the margin, and you have the pack size you need. That single number eliminates most of the market before you look at a single review — the full comparison is in the mower roundup.
Measuring your lawn
- Break it into rectangles. Front, back, side strip. Almost every lawn decomposes into three or four.
- Pace each one. A normal adult stride is close to 3 feet. Length times width gives you square feet per section.
- Add them up, then subtract the beds. Planting beds, the driveway and the patio are not lawn, and on a small lot they can be a third of the footprint.
- Check against the reference figures. 10,890 sq ft is a quarter acre, 21,780 is a half, 43,560 is an acre.
When is a wider deck worth it?
Between 20 and 21 inches, barely. That is about a 5% difference in coverage, which on a quarter-acre lawn is roughly a minute. The 20-inch mower is lighter (57.5 lb published against 75 lb for a 21-inch self-propelled) and cheaper, and on a small lot both of those matter more than the minute.
Between 21 and 42 inches, enormously. Coverage doubles and speed roughly triples, which is why the transition happens at about an acre and why it is a transition in machine type rather than a step up in deck size — the riding mower page runs that math.
Three things that override the table
- Slope. Any real gradient means self-propelled regardless of lawn size — the reasoning is here.
- Obstacles. A lawn full of trees, beds and a swing set slows a wide deck disproportionately. Narrow decks turn tighter.
- Storage. A 42-inch riding mower needs somewhere to live. If that somewhere does not exist, the table's recommendation is theoretical.
The products discussed
Specs are the manufacturer's own and linked to the page they came from. Prices come from a live daily check; where we have no verified price we say so rather than print a stale one.
Greenworks 40V 20" Push LM2054
Greenworks · Greenworks 40V · Our score 8.0/10
#ad No verified live price right now, so we show none rather than a stale one. How we're funded.
40 minutes on a 160Wh pack and 57.5 lb to push -- the honest answer for a third of an acre and nothing more.
Published specs
| Model / SKU | LM2054 / 2549902 |
|---|---|
| Deck | 20 in |
| Max blade speed | 3200 RPM |
| Battery included | 40V 4.0Ah |
| Cut height | 1.2-3.6 in, 7 positions |
| Runtime claim | Up to 40 min |
| Weight | 57.5 lb |
| Rated for | Up to 1/3 acre |
| Warranty | 3-yr tool / 3-yr battery |
Source: 40V 20" 4-in-1 Push Lawn Mower (LM2054), greenworkstools.com
40V x 4.0Ah = 160Wh. Note it claims 40 minutes on 160Wh where the 80V flagship claims 33 minutes on 320Wh -- a 20 in deck and no self-propel drive motor is why.
What the numbers favor
- Lightest published weight on this page at 57.5 lb, and the only sub-60 lb mower here
- Claims 40 minutes from 160Wh -- the best published minutes-per-watt-hour of any mower on this page
- Same 3200 RPM blade speed as the 80V flagship
- 4-in-1 deck at the entry price
What they don't
- Push only -- no drive assist on any slope
- 1.2 in minimum cut height is lower than most cool-season lawns should ever be cut
- 120-minute recharge, three times the 80V model's 40 minutes
your lawn is over a third of an acre or has any real slope. Greenworks rates it to 1/3 acre and you will be pushing all 57.5 lb of it up the hill yourself.
How it scores
Scores are our editorial weighting of the published specs above, not a test result. They are deliberately kept out of this page's structured data.
EGO Power+ 21" Select Cut LM2135SP
EGO · EGO 56V ARC Lithium · Our score 9.1/10
#ad No verified live price right now, so we show none rather than a stale one. How we're funded.
The most watt-hours in the box of any flagship walk-behind here, on the platform with the widest tool range to grow into.
Published specs
| Deck | 21 in |
|---|---|
| Cutting torque | Up to 7.0 ft-lbs |
| Battery included | 56V 7.5Ah |
| Cut height | 1-4 in, 8 positions |
| Self-propel speed | 0.9-3.1 MPH |
| Runtime claim | Up to 60 min |
| Warranty | 5-yr tool / 3-yr battery |
Source: EGO POWER+ 21" Select Cut System (LM2135SP), egopowerplus.com
56V x 7.5Ah = 420Wh, using EGO's advertised pack voltage.
What the numbers favor
- 420Wh in the box -- the largest included pack of any flagship walk-behind on this page
- Eight cut-height positions from 1 to 4 in, the widest published range here
- Three interchangeable lower blades (mulching, high-lift bagging, extended runtime)
- 5-year tool warranty, the longest published on this page
What they don't
- EGO publishes torque (7.0 ft-lbs), not motor wattage, so it cannot be compared directly against Greenworks' 1500W figure
- The 7.5Ah pack that earns the runtime claim is also the expensive one to replace
your yard is under a quarter acre. You would be paying for 420Wh of headroom you will never discharge, and a 20 in push mower cuts the same grass.
How it scores
Scores are our editorial weighting of the published specs above, not a test result. They are deliberately kept out of this page's structured data.
Kobalt 80V Max 21" Self-Propelled (dual-port)
Kobalt · Kobalt 80V Max · Our score 8.4/10
#ad No verified live price right now, so we show none rather than a stale one. How we're funded.
Two 4Ah bays, 80 published minutes and an acre rating -- the most runtime per purchase of any 80V walk-behind here.
Published specs
| Deck | 21 in, steel |
|---|---|
| Motor | Brushless |
| Batteries included | 2 x 80V 4.0Ah (dual port) |
| Runtime claim | Up to 80 min |
| Rated for | Up to 1 acre |
| Drive | Self-propelled RWD, 7 speed settings |
| Recharge | Approx. 60-90 min |
Source: Kobalt 80-Volt 21-in Self-propelled Battery Mower (2 batteries), lowes.com
80V x 4.0Ah = 320Wh per pack; two bays = 640Wh installed. Kobalt's listing does not state whether the two ports discharge simultaneously or in sequence, so we do not claim either -- what is verifiable is that 640Wh is on the machine when you start.
What the numbers favor
- 640Wh installed across two bays, the most of any walk-behind on this page
- Rated to 1 acre, twice the Greenworks 80V flagship's half-acre rating
- Seven published speed settings on the self-propel drive
- All Kobalt 80V packs are cross-compatible across the 80V outdoor line
What they don't
- Sold through Lowe's only, so availability and price track one retailer
- The listing does not publish weight, cut-height range or a noise figure
- Kobalt's 80V outdoor range is narrower than EGO's or Ryobi's
you want a platform rather than a mower. Kobalt is a single-retailer house brand -- fine for the tool, thinner as a decade-long ecosystem bet.
How it scores
Scores are our editorial weighting of the published specs above, not a test result. They are deliberately kept out of this page's structured data.
EGO Power+ Z6 42" Zero Turn ZT4204L
EGO · EGO 56V ARC Lithium · Our score 8.8/10
#ad No verified live price right now, so we show none rather than a stale one. How we're funded.
2,240Wh of the same 56V packs that run the rest of your yard, and a published two acres on a charge.
Published specs
| Deck | 42 in |
|---|---|
| Power claim | 22 HP gas equivalent |
| Top speed | 8 MPH |
| Batteries included | 4 x 56V 10.0Ah |
| Bay capacity | Up to 6 packs |
| Coverage | Up to 2 acres per charge |
| Warranty | 5-yr tool, battery and charger |
Source: POWER+ 42" Z6 Zero Turn Riding Mower (ZT4204L), egopowerplus.com
56V x 10.0Ah = 560Wh per pack. Four packs = 2,240Wh; six bays filled = 3,360Wh. Against the published 2 acres on four packs, that is roughly 1,120Wh per acre -- the number to size any electric riding mower against.
What the numbers favor
- Uses the identical 56V ARC Lithium packs as EGO's handheld tools -- the batteries are not stranded
- Six battery bays, so range is a purchase decision rather than a fixed limit
- 5-year warranty covering tool, battery AND charger
- 32 published LED lights, which matters more than it sounds for dusk mowing
What they don't
- Four 10.0Ah packs is a substantial share of the purchase price on its own
- EGO's published watt-hour figure for this configuration does not reconcile with 56V x 10.0Ah x 4; we publish our own arithmetic (2,240Wh) and show the working rather than repeat a number we cannot verify
your lot is under an acre. A 21 in walk-behind finishes a half acre in the time it takes to get a zero turn out of the shed, and costs a fifth as much.
How it scores
Scores are our editorial weighting of the published specs above, not a test result. They are deliberately kept out of this page's structured data.
Common questions
What size mower do I need for my yard?
What size mower for half an acre?
What size mower for a quarter acre?
Does a wider deck really save much time?
How do I measure my lawn?
Sources
- Greenworks 40V 20" 4-in-1 Push Lawn Mower (LM2054), greenworkstools.com
- EGO POWER+ 21" Select Cut System (LM2135SP), egopowerplus.com
- Kobalt 80-Volt 21-in Self-propelled Battery Mower, lowes.com
- EGO POWER+ 42" Z6 Zero Turn Riding Mower (ZT4204L), egopowerplus.com
- Greenworks 80V 21" Self-Propelled Mower (LM2108S), greenworkstools.com
Read next
- Guides
The questions that come before the shopping. Answered in the first paragraph, then explained.
- Best battery lawn mower for a small yard
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- Best electric mower for a half acre to an acre
Half an acre and up, runtime is the whole problem. Ranked on installed watt-hours and acreage rating.
- Best electric riding mower for 2026
Electric zero turns ranked on installed watt-hours and the energy-per-acre figure.
- How much should I spend on a lawn mower?
Why we will not print a price, and the cost-per-watt-hour math to run instead.