How Often To Sharpen Mower Blades, And How To Make Them Last Longer

Early on in my lawn mowing career, I realized that I probably wasn't sharpening my mower blades as often I was supposed to. Thankfully, a local lawn service place at the time was helpful in giving me some pointers, and I recently did some additional research online to confirm what I learned several years ago. Here's what I found...

For most rotary (motorized) mowers, I recommend sharpening the blades every 20-25 hours. For a lawn that takes about 45 minutes to mow, that means you should sharpen your mower blades every 26-33 mowing sessions.

As you can imagine, there are many variables -- such as how long it takes to mow your lawn, how often you mow throughout the year, and so on -- that make it difficult to give a "one size fits all" answer. So the real question you should be asking is...

How Many Hours Do Mower Blades Last?

Well as indicated earlier, most mower blades will last about 20-25 hours until they should be sharpened. But in terms of overall lifetime, most blades last at least 100-200 hours total, and some higher quality ones can last even longer, as much as 400 hours.

Of course if you're not careful and let stones and big sticks get caught up in the mower, you'll notice the blades get nicked and warn down much sooner, but we'll get into that a little later.

While we're still on the topic of the average mower blade lifetime, I've done the math for you and figured out about how long your mower blades may last based on how long it takes to mow your lawn, and assuming that most people mow their lawns 15-25 times per year (which depends on a combination of climate and personal preference). Here's the math...

Time To Mow Lawn

Sharpen After...

Sharpen Every...

15 minutes

80-100 sessions

Every 3-4 years

30 minutes

40-50 sessions

Every other year

1 hour

20-25 sessions

Once per year

1 hour 30 minutes

13-17 sessions

Once or twice per year

2 hours

10-13 sessions

Twice per year

How Can I Tell When My Mower Blades Need To Be Sharpened?

While the table above is certainly a helpful reference, it's more important that you learn what indicators to look out for so you know when it's time to sharpen your mower blades again, even if "the data" says it's not time yet.

When looking at the mower blade itself, look for any obvious dents or major scratches. You'll likely see hairline nicks over time, but very small nicks can be worked out during sharpening. However, if you notice bigger dents or nicks that have bent even a tiny portion of the blade up or down, it's unfortunately time to replace the entire blade (find a replacement blade here).

Another indicator to look for is the grass itself. Look closely at the blades of grass to see how clean of a cut the mower made. If you notice that the tips of the grass blades look torn and ragged, that probably means your mower blades should be sharpened.

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How Can I Make My Mower Blades Last Longer?

You may have pieced together the answer to this question from what you've read so far, but just to be clear, here are a couple pointers to keep in mind to help keep your mower blades lasting as long as possible.

First of all, before you begin mowing, look around the lawn for any big sticks, big branches, stones, rocks, or little toys (if you have kids) so that you don't accidentally run over them while you're mowing and mess up the mower blades. Remember, messing up the mower blades means you'll need to replace them, not simply sharpen them.

Second, make sure you remember to sharpen the blades frequently (I recommend every 20-25 hours of use) and don't assume that it's time to replace the blades if you haven't tried sharpening them first.

Lastly, make sure you learn how to sharpen your blades properly so you don't accidentally wear off more of the blade than is necessary. In other words, if you sand off too much of the blades each time you're sharpening them, before you know it you'll have to replace the entire blade.

Lawn Mower Blade Sharpening Cost

If you plan to sharpen your mower blade yourself, the only expenses involved are the cost of the blade sharpener and the "cost" of your time. A basic blade sharper (which is fine for most cases) can typically be found for less than $20.

But if you'd rather let a pro do it for you, you may find that your local mower sales/repair shop would sharpen the blade for about $10 (I've heard of some people getting it done for as low as $5 but that's not common).

Just be aware that some repair shops offer that service "at cost" meaning they don't make a profit from sharpening the blades, and they use it as an opportunity to try to get you to buy a new mower blade. So do your research ahead of time and decide for yourself if your blade is fine being sharpened or if its too far gone and you really just need a replacement.

If you sharpen your blade twice a season then you'll pay for the cost of the sharper tool in just one season.

Also keep in mind that you can get a cheap mower blade online for around $20-$30 depending on your mower. So although I do recommend sharpening your mower blade until it can't be sharpened anymore, I also recommend replacing the entire blade before it's too far gone.

Pro Tip: Keep A Spare Blade On Hand

Especially if you need to sharpen your blades more than once per year, you may want to keep a spare already-sharp blade on hand so that when you notice your current blade is getting dull, you can replace it and then sharpen the old blade later when you have more time. This way you'll just be rotating out two blades over time, and it'll be longer until you need to buy another.

If you want to have a spare blade on hand, you can find one that fits your brand/model mower here on Amazon.

Benefits Of Keeping Your Mower Blades Sharp

The obvious benefit of sharpening your mower blades regularly is that your grass will look nicer. A dull blade doesn't cut grass properly and can leave it looking ragged and torn.

But it's also important to note that when you mow with dull mower blades and as a result tear up the grass blades, your lawn becomes more likely to be affected by diseases.

Do Brand New Mower Blades Need To Be Sharpened?

No, most new mower blades do not need to be sharpened. Although rare, some blades may come with a small coat of paint in which case it may seem beneficial to "sharpen off" the paint. That said, that thin layer of paint will probably wear off with use anyway, so is it really worth the hassle?

Want my recommendation?

Don't worry about sharpening a new mower blade. But if you're really concerned, then before sharpening it just mow a small, less-visible part of your lawn and look at the grass blades afterward. If the grass blades are nicely cut then don't waste your time sharpening the mower blades.

In Conclusion

Hopefully I've answered most or all of your questions about how often you should sharpen your mower blades, but if I missed anything, please feel free to ask in the comments below and I'll do my best to point you in the right direction.

Remember, take care of your mower blades by sharpening them regularly. In doing so, you'll be keeping your grass looking clean-cut and will help prevent diseases from overtaking your lawn.

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Ed Kirkland

Hi, I'm Ed, and I've been doing lawn work since my mid teen years, picking up jobs here and there mowing and helping with basic landscaping projects. I worked at a couple different lawn care / landscaping companies throughout my college years, and now thanks to the internet I'm able to make a share my knowledge and advice with people about lawn care and landscaping.

Click Here to Leave a Comment Below 1 comments
Mindy Jollie - July 30, 2019

I like what you said about keeping an extra mower blade on hand in case something happens.


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