The 1/3 rule
Never remove more than a third of the grass blade in one mow. It's the single most-broken rule in residential lawn care, and the reason warm-season lawns get scalped and cool-season lawns get stressed.
- Pick your target height (the calculator does this for you).
- Mow when the grass reaches 1.5× that height, not before and not long after.
- If you've waited too long, raise the deck to bring the canopy down in two passes a few days apart, never one big chop.
Cutting more than a third stresses the roots and exposes soil to weed seeds. The grass uses energy regrowing the canopy instead of building roots.
Mowing height by grass type and season
Cool-season grasses go up in summer to shade the soil. Warm-season grasses stay short year-round.
Swipe sideways to see every column.
| Grass | Group | Spring | Summer | Fall | Winter |
|---|---|---|---|---|---|
| Bermudagrass | Warm-season | 1.5″ | 1.5″ | 2″ | 2″ |
| Zoysia | Warm-season | 1.5″ | 2″ | 2″ | 2″ |
| St. Augustine | Warm-season | 3.5″ | 4″ | 3.5″ | 3.5″ |
| Centipede | Warm-season | 1.5″ | 2″ | 2″ | 2″ |
| Bahiagrass | Warm-season | 3″ | 3.5″ | 3″ | 3″ |
| Tall fescue | Cool-season | 3.5″ | 4″ | 3.5″ | 3.5″ |
| Kentucky bluegrass | Cool-season | 3″ | 3.5″ | 3″ | 3″ |
| Ryegrass | Cool-season | 2.5″ | 3″ | 2.5″ | 2.5″ |
| Fine fescue | Cool-season | 3″ | 3.5″ | 3″ | 3″ |
| Kikuyugrass | Warm-season | 1.5″ | 1.5″ | 1.5″ | 2″ |
| Annual ryegrass | Cool-season | 2″ | 2.5″ | 2″ | 2″ |
| Cool-season mix | Cool-season | 3″ | 3.5″ | 3″ | 3″ |
| Carpetgrass | Warm-season | 1.5″ | 1.5″ | 1.5″ | 2″ |
Heights are inches measured at the deck. Reel and robotic mowers can run ¼″ lower than these targets.
How often to mow
Across the year, frequency changes much more than height. The mowing-season heat strip in the preview shows your weekly cadence.
Swipe sideways to see every column.
| Grass | Growth | Spring | Summer | Fall | Winter |
|---|---|---|---|---|---|
| Bermudagrass | fast | 5 d | 4 d | 7 d | 14 d |
| Zoysia | medium | 7 d | 5 d | 10 d | 21 d |
| St. Augustine | fast | 7 d | 5 d | 10 d | 21 d |
| Centipede | slow | 10 d | 7 d | 14 d | 28 d |
| Bahiagrass | medium | 7 d | 5 d | 10 d | 21 d |
| Tall fescue | fast | 5 d | 7 d | 5 d | 14 d |
| Kentucky bluegrass | medium | 5 d | 7 d | 5 d | 14 d |
| Ryegrass | fast | 5 d | 7 d | 5 d | 14 d |
| Fine fescue | slow | 7 d | 10 d | 7 d | 14 d |
| Kikuyugrass | fast | 5 d | 4 d | 7 d | 14 d |
| Annual ryegrass | fast | 5 d | 14 d | 5 d | 7 d |
| Cool-season mix | medium | 5 d | 7 d | 5 d | 14 d |
| Carpetgrass | slow | 10 d | 7 d | 14 d | 28 d |
Days between mows. "Winter" means dormant or near-dormant, when most warm-season lawns don't need cutting.
What mower to use
- Rotary (push or riding) is the right tool for almost every U.S. lawn. It handles ½″ to 4½″ heights and tolerates uneven ground.
- Reel mowers cut cleaner and lower, which is why low-cut warm-season lawns (Bermuda, Zoysia at golf-course heights) and the obsessed homeowner reach for them. Need flat, even turf.
- Robotic mowers cut a tiny bit every day, so they violate the 1/3 rule the gentle way (taking a sliver each time). Best paired with a flat lawn and a known irrigation pattern.
Three small habits that change the lawn
- Mulch the clippings. They return ~25% of the lawn's annual nitrogen and decompose in 2–3 weeks, not the months people imagine.
- Sharpen the blade twice a year. A dull blade tears the leaf tip and turns it brown within a day, which is why some lawns look stressed even on a perfect schedule.
- Mow in alternating directions. Always pushing the same way over time leans the grass and packs the soil ruts in a wheel pattern.