What Lawn Mower Blade Do I Need?

Approx Reading Time: 9 minutes

Using the right lawnmower blade is more important than it may seem.

The blade of the lawnmower is what, to a huge extent, determines the quality of the cut. The blade has a big say in whether or not you will end up with a clean-cut lawn or not.

And this is something that I myself was very interested in. People always talk about what lawnmower blade they use and how they have a few different types of blades.

So, what lawn mower blade do you need? The lawn mower blade you need will vary depending on different factors like your lawn mower model, its capabilities, the type of cut you are after, and even the grass conditions and time of the year. The right lawn mower blade needs to fit perfectly on your mower and suite to your needs.

As it stands, there is more to these blades than meets the eye.

Certain characteristics separate them and make them excel at different aspects of mowing. Let’s take a look.

What Type of a Lawnmower Blade Do You Need?

People have been using lawnmowers for quite some time now, so they definitely had enough time to optimize the whole process of cutting a lawn.

Naturally, there are a few different types of lawnmower blades that have been invented and are still in use today.

Certain blades will perform better at certain tasks. Depending on your goals and preferences, you may need just one or a few different types of blades.

There are several types of lawnmower blades:

Standard (Deck) Blade

This is the most commonly used type of blade. New lawnmowers often come with a deck blade installed on them. However, this does not necessarily mean that this is going to be the best blade for you.

The deck blade is best used for regular cutting of well-maintained lawns.

The standard blade is straight, and it is not suitable for tall grass, as it does not provide good lifting or mulching capabilities.

Lifting Blades

These blades feature a slight curve (or a lift) right behind the cutting edge. The lift creates better air movement and suction of the grass clippings.

This makes them suitable for bagging and side discharging. However, the lifting blades are not designed for mulching.

The curve can vary from low to extremely high.

  • Low lifting blades are great for dusty and sandy terrain because they will cut the grass while keeping the dust and debris from spreading;
  • Medium lifting blades are suitable for relatively well-maintained lawns, and they can cut even slightly damp grass; and
  • High and extremely high blades are ideal for cutting tall and thick grass. They have superior side discharge capabilities but should not be used in dusty and sandy terrain.

In other words, the more exaggerated the curve, the stronger the suction will be resulting in finer cut and cleaner lawn.

However, this comes at a price. The lift creates more strain on the engine; thus, the higher the lift, the more powerful the engine should be.

Notched (Rolled) Blades

These are very similar to the standard lifting blades as they feature curved edges too.

The only difference is that the curve begins with a notch. This creates a stronger airflow, which expels the grass cuttings at a much faster rate.

The notched blades are ideal for bagging and cutting high or moist grass.

Mulching Blades

Mulching blades are easy to spot. They are curved and have a longer cutting edge.

Mulching blades are designed to mulch grass and leaves. However, they are not the best at suction and side discharging the grass.

Toothed (Or Gator) Blades

Gator blades are like upgraded mulching blades. If you want a blade that can be used for mulching, side discharging, and bagging, this is the blade you need.

You cannot really mistake them; they have usually three curved teeth right behind the cutting edges.

These teeth significantly improve the lifting and the discharge power, while at the same time produce very finely-shredded grass cuttings.

What Size of a Lawnmower Blade Do You Need?

You might have noticed that lawnmowers are usually labeled with different sizes. The same holds true when you look at the blades; there can be 21-inch blades or even 42-inch blades.

But then if you take a closer look, you will find something very interesting. A 21-inch blade will not look very different compared to a 42-inch blade (maybe just a few inches larger).

So, how are mower blades categorized by size, and how to find out what blade size you need?

The deck size of your lawnmower determines the size of the blade you need.

This is why a 42-inch blade will not be a lot longer than a 21-inch blade; the 42-inch blade is designed for use in 42-inch lawnmowers, which usually have two blades that overlap. Or in other words, you will not need a really long blade.

How to Find the Size of the Lawnmower Blade You Need?

You need to measure several different aspects of the blade in order to make sure you have everything covered.

  1. The length of the blade – The length is measured diagonally from cutting tip to cutting tip;
  2. The center hole – You need the diameter of the center hole as well as its type;
  3. The outer holes – In a similar fashion; the diameter of the outer holes needs to be measured and then the distance between the centers of the two outer holes;
  4. The width of the blade – The width of the blade is measured at its center; and
  5. The thickness of the blade – The thickness is measured at the center of the blade as well.

Does the Blade Size Matter?

The size of the blade a lawnmower uses is one of the essential aspects when buying a new blade.

The blade size determines the size of the cut, and it needs to match your mower’s deck size.

There is another aspect of the blade’s size. And that is mowing time.

The bigger the area you need to cut, the bigger the lawnmower you will generally need. And a bigger lawnmower (with a bigger blade) can reduce the mowing time significantly.

Can You Use a Bigger Blade?

Lawnmower decks are designed to accommodate blades with a specific length.

In most cases, the blade stands at about 1/2 of an inch away from the deck. This does not give you a lot of leeway.

Lawnmowers should not be run with a longer blade than what is recommended by the manufacturer.

A longer blade will usually not fit. But even if it fits, there is a higher chance of damaging the blade, the deck, and the engine.

Also, it is a severe health hazard; do not do it.

Can You Use a Smaller Blade?

You may ask me, “Okay, if I cannot fit in a bigger blade, what about a smaller blade?”

In practice – this is true – a smaller blade can be installed on any lawnmower (provided the mounting fits). But are there going to be any consequences of doing so?

Using a smaller lawnmower blade is not recommended, because this can damage the lawnmower, the blade, and the person operating the mower.

Lawnmowers are usually fine-tuned to work with blades of a specific size.

A smaller blade can potentially lead to some problems; the blade may spin at faster RPMs, the engine may end up maintaining higher output or torque, and there could be unsafe levels of vibrations.

A smaller blade is going to be, again, a health hazard.

Can You Use Lawnmower Blades From Different Manufacturers?

Many of the lawnmower blades are interchangeable. With time mower blades across the board have been very standardized.

However, there is a little caveat here.

To use a different blade, either a replacement or a borrowed one from a different mower, you need to make sure that everything fits perfectly; the center hole, the length of the blade, the outer hole’s size and spacing, the width and thickness.

As long as everything matches, the blades should be good to go.

If something does not match, it is not recommended to swap the blades.

Is There a Difference Between the Aftermarket and Original Blades?

Sooner or later, every owner of a mower is faced with the dilemma of choosing between original (OEM) blades and aftermarket replacement blades.

Original mower blades are usually designed explicitly with the idea to fit on certain lawnmowers. They are like a puzzle piece that fits perfectly. And the original blades will be the same as the ones your lawnmower initially came with.

Original blades are also held to higher standards of quality. Usually, going with an original part is better than buying a replacement part from some obscure company.

But that is not always 100% true.

Aftermarket blades are not necessarily worse compared to an OEM product.

Here’s the thing.

First, it depends on the blades.

It is a well-known fact that some aftermarket blades are manufactured by the same companies that make the original blades – the only thing that may be missing sometimes is the branding.

And secondly, as a direct result of that, the aftermarket blades are almost universally going to be significantly cheaper compared to their original counterparts.

On the other hand, some aftermarket blades may be held to lower quality standards.

In other words, the blades that did not pass the quality check for a certain brand may be sold as aftermarket blades. And some may not even fit your mower due to poor design.

Before installing an aftermarket blade on your mower, make sure that your mower’s warranty will not be voided.

Some manufacturers will not honor the warranty if the mower has been altered in any way, including installing an aftermarket blade.

As it stands, you do not necessarily need to buy original lawnmower blades. Buying aftermarket blades is okay as long as the necessary due diligence is carried out in advance.

Peter Toth

Hi! I'm Peter, the owner of BackyardGadget. Working around the house has always been a big part of my life. I've created this site to share my experience, and to help people choose the right tools for the job. Thank you for stopping by!