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How many minutes does your lawn take, and will the battery last?
Updated
Enter the grass you mow. The calculator turns it into minutes for each mower's deck width, then sets that against the runtime the maker claims. You get one of three answers per mower: one charge, two charges, or too small for this lawn.
Mowing time and battery calculator
An estimate, not a measurement. Minutes needed = square feet / (deck width less a 2 inch overlap) / pace, plus extra for turns and edges. The share of the claimed runtime we count on for each kind of grass is our own estimate. Makers do not publish one. An acre is 43,560 sq ft.
How the math works
A mower cuts a strip as wide as its deck. You overlap each pass a little so you do not leave a stripe. We use a 2 inch overlap. So a 21 inch deck cuts 19 inches of fresh grass per pass. Divide your square feet by that width and you get the feet you walk. Divide by your pace and you get minutes. Then we add time for turns, edges and working around things: 10 percent for an open rectangle, 20 percent for an average yard, 35 percent for a yard full of trees and beds. Those three figures are our estimates.
The default pace is 2.5 mph. The CDC counts walking at 2.5 mph or faster as brisk walking. For a second reference, EGO lists the drive speed on one of its 21 inch self-propelled mowers as 0.9 to 3.1 mph. So 2.5 mph is a steady mowing pace, and 3 mph is near the top of what that drive will do.
Why we do not count on the full claimed runtime
Runtime claims start with "up to". Greenworks adds that its figure "varies based on grass condition and operator technique". No maker here says how much. Owner reports on the same mower can run from 45 minutes down to 15. So we plan on 100 percent of the claim only for short, dry, thin grass, 80 percent for normal weekly growth and 60 percent for thick, tall or damp grass. Those shares are our estimate. If you mow every week in dry weather you will do better than if you let it go for two.
Worked examples
All at 2.5 mph, average yard, normal weekly growth.
| Grass to mow | EGO LM2114 21 in push | EGO LM2114SP 21 in | Greenworks 60V 21 in SP | Greenworks 40V 16 in | WORX WG779 14 in | LawnMaster 19 in |
|---|---|---|---|---|---|---|
| 2,500 sq ft (small town lot) | 9 min. One charge | 9 min. One charge | 9 min. One charge | 12 min. One charge | 14 min. One charge | 10 min. One charge |
| 5,000 sq ft | 17 min. One charge | 17 min. One charge | 17 min. One charge | 23 min. One charge | 27 min. One charge | 19 min. One charge |
| 8,000 sq ft | 28 min. One charge | 28 min. One charge | 28 min. One charge | 37 min. Two charges | 44 min. Two charges | 31 min. One charge |
| 10,890 sq ft (1/4 acre of grass) | 38 min. One charge | 38 min. One charge | 38 min. One charge | 51 min. Two charges | 59 min. Two charges | 42 min. Two charges |
| 14,520 sq ft (1/3 acre of grass) | 50 min. Two charges | 50 min. Two charges | 50 min. Two charges | 68 min. Three or more | 79 min. Three or more | 56 min. Two charges |
Take 8,000 sq ft with the Greenworks 40V 16 in. Its 16 inch deck cuts 14 inches of fresh grass per pass, so you walk 6,857 ft. At 2.5 mph that is 220 ft per minute, and with 20 percent added for turns it comes to 37 minutes. We plan on 32 of its 40 claimed minutes. So it needs a second charge. The EGO LM2114 21 in push needs 28 minutes for the same lawn and we plan on 44, so one charge does it.
- 2,500 sq ft9 minutes
- 5,000 sq ft17 minutes
- 8,000 sq ft28 minutes
- 10,890 sq ft38 minutes
- 14,520 sq ft50 minutes
If the answer is two charges
You have three choices. Buy a kit with two batteries, like the Greenworks 60V 21 in SP. Buy a second battery for the mower you like. Or stop and recharge, which takes 80 minutes on the EGO LM2114 21 in push and 120 minutes on the Greenworks 40V 16 in, per the makers. More on the battery page.
Work out your own lawn with the mowing time calculator, or compare all six picks on the roundup page.