How Sharp Should Your Lawn Mower Blade Be?

A sharp mower blade is one of the simplest things you can do for a healthier, better-looking lawn. Yet it's one of the most commonly neglected maintenance items we see.

A dull blade doesn't cut grass — it tears it. Torn grass blades have ragged edges that turn brown and are more susceptible to disease and pest damage. If your lawn looks brownish a day or two after mowing, dull blades are likely the reason.

How often should you sharpen? The general rule is every 20-25 hours of mowing. For most homeowners mowing once a week, that's roughly twice per season — once at the start and once midway through. If you hit rocks, roots, or other debris, get the blade sharpened sooner.

What does a properly sharpened blade look like? Think butter knife, not razor blade. A mower blade should be sharp enough to cut grass cleanly but doesn't need to be razor-sharp. An edge that's too thin will dull faster and is more prone to nicking.

How do you know it's time? Look at your grass after mowing. Clean, straight cuts mean your blade is sharp. Ragged, torn tips mean it's dull. You can also visually inspect the blade — if the cutting edge is rounded, has visible nicks, or is no longer defined, it needs sharpening.

When should you replace instead of sharpen? Replace the blade if it's bent (even slightly — lay it on a flat surface to check), cracked, has thin spots from repeated sharpening, or has deep gouges that can't be ground out.

We sharpen blades for $10 per blade, and most push mower blades can be sharpened in about 15 minutes while you wait. We also balance blades after sharpening — an unbalanced blade causes vibration that wears out engine bearings and spindles prematurely.