Robot Lawn Mower Size Calculator

One rated for more than your actual grass area. Makers rate area for an open, simple lawn, so we add 15 percent for an open lawn, 20 percent with some trees and beds, and 30 percent for a complex yard with many obstacles or narrow passages.

RTK mowers navigate by satellite with a reference station and are accurate to a few centimeters under open sky, but tree canopy and buildings can block the signal. LiDAR mowers map the yard with a spinning laser and cameras recognize grass edges and obstacles, so both cope better under trees. Many current mowers combine two of these.

Most current models do not. They use RTK, LiDAR or cameras with boundaries you draw in an app. Wire-guided mowers still work well under heavy tree cover, but installing the wire takes time.

Most mowers in our list are rated for 35 to 50 percent. The steep-slope all-wheel-drive models go to 60, 80 and 84 percent. Measure the steepest spot: a 45 percent slope rises 4.5 ft over 10 ft of ground.

It mows several times a week on a schedule, so the grass stays short without bagging, and you stop spending weekend hours mowing. The trade-offs are the upfront cost, an app setup, and edges that may still need a trimmer.

Break the grass into rectangles, multiply length by width for each, and add them up. Count only grass, not the house, driveway, patio or beds, because lot size overstates the mowing area. One acre is 43,560 sq ft, so a quarter acre is 10,890 sq ft and a half acre is 21,780 sq ft. Online satellite map tools with an area measure give a close estimate if you cannot pace it out.

A half acre is 21,780 sq ft of grass, which becomes about 25,047 sq ft with 15 percent headroom for an open lawn and 28,314 sq ft with 30 percent for a complex yard. That rules out mowers rated for exactly 1/2 acre and points to models rated for 3/4 acre (32,670 sq ft) or more, such as the ECOVACS GOAT A3000 LiDAR or Mammotion LUBA 3 AWD 3000. Then check the slope rating and, under trees, that it has LiDAR or vision.

Not always. Classic RTK mowers use a reference station mounted with a clear view of the sky, but the WORX Landroid Vision Cloud and Segway Navimow i210 AWD use network or cloud RTK with no antenna to install. LiDAR and vision mowers such as the Segway Navimow i215 LiDAR, ECOVACS GOAT A3000 LiDAR and Dreame A3 AWD Pro need neither an RTK station nor a wire.

The mowers in this tool that list it range from as low as 1 in to as high as 4 in, but each model covers only part of that. The Mammotion LUBA 3 AWD 3000 tops out at 2.7 in and the Mammotion LUBA 2 AWD 5000HX starts at 2.2 in. Check that the range covers the height you mow at now.

The models in this tool that publish a noise rating list 55 to 60 dBA, from 55 dBA for the Sunseeker V3 to 60 dBA for the Sunseeker S4 and X5 AWD. That is far quieter than a gas mower. If you plan early-morning runs, check any local noise rules first.