What Size Blade Should I Use for My Lawn Mower?

Getting that perfect, lush lawn is a dream for many homeowners. But achieving it requires more than just watering and fertilizing. Choosing the right mower blade is crucial for a healthy, even cut. This guide will delve into the world of mower blades, covering everything from understanding blade sizes to choosing the right one for your specific needs. You’ll learn how different blade sizes impact your lawn’s appearance, the importance of blade sharpness, and how to safely replace your blades.

Understanding Blade Sizes and Their Impact

A mower blade’s size is directly related to its cutting width and the overall performance of your mower. Blade size is typically measured in inches, and it’s not just a matter of choosing the largest blade possible. The optimal blade size depends on several factors, including your lawn’s size, the type of grass you have, and the desired cut height.

Factors to Consider When Choosing a Blade Size

Several key factors influence your blade size selection. Let’s break down the most important ones:

1. Lawn Size and Mower Type

  • Small Lawns: For small lawns, a 16-18 inch blade is usually sufficient. Smaller blades are often found on push mowers and small riding mowers.
  • Large Lawns: Larger lawns benefit from wider blades, typically 20-22 inches. These blades are found on larger riding mowers and can significantly reduce mowing time.
  • Rotary vs. Reel Mowers: Rotary mowers use a spinning blade to cut grass, while reel mowers use a set of blades that rotate against a stationary blade. Rotary mowers typically use larger blades than reel mowers.

2. Grass Type

Different types of grass require different cutting heights. Here are some general guidelines:

  • Fine-Bladed Grasses: For fine-bladed grasses like fescue or bentgrass, you’ll want a shorter cut height. This typically requires a sharper blade with a smaller cutting width.
  • Coarse-Bladed Grasses: Coarse-bladed grasses like Bermuda or St. Augustine grass can handle a higher cut. A larger blade can help you achieve a more even cut for these thicker grasses.

3. Desired Cut Height

The desired cut height is crucial in determining the appropriate blade size. Here’s why:

  • Lower Cut Heights: For a lower cut height, a smaller blade with a sharper edge is typically better. This ensures a clean, precise cut without tearing the grass.
  • Higher Cut Heights: For a higher cut height, a larger blade can be more efficient. It allows you to cover more ground with fewer passes, reducing mowing time.

The Importance of Blade Sharpness

Blade sharpness plays a significant role in the health and appearance of your lawn. Here’s why:

  • Clean Cuts: A sharp blade cuts grass cleanly, preventing tearing and brown tips. This promotes healthier growth and a vibrant green lawn.
  • Reduced Stress: A sharp blade minimizes stress on your grass, allowing it to recover quickly from mowing.
  • Efficient Cutting: A sharp blade requires less power to cut grass, saving energy and extending your mower’s lifespan.

Signs of a Dull Blade:

  • Uneven Cutting: If you notice uneven cuts, with some grass blades appearing longer than others, it’s a sign of a dull blade.
  • Torn Grass: A dull blade will tear the grass instead of cutting it cleanly. This can leave brown tips and affect your lawn’s overall health.
  • Increased Mower Effort: You’ll likely notice that your mower is struggling to cut the grass if the blade is dull. This is a clear indicator that it’s time for a sharpening or replacement.

How to Sharpen Your Mower Blade

Sharpening your mower blade is a relatively simple task that can be done at home. Here’s what you’ll need:

  • A sharpening stone or file: You can find these at most hardware stores.
  • A vise or clamp: This will hold the blade securely in place while you sharpen it.
  • Safety gear: Always wear safety glasses and gloves when handling sharp objects.

Sharpening Steps:

  1. Remove the blade: Carefully remove the blade from your mower. Be sure to disconnect the spark plug or battery to prevent accidental starting.
  2. Secure the blade: Place the blade in the vise or clamp. Ensure it’s securely held in place.
  3. Sharpen the cutting edge: Using the sharpening stone or file, slowly sharpen the cutting edge of the blade. Make sure to maintain a consistent angle throughout the entire length of the blade.
  4. Check the balance: After sharpening, check the blade for balance. An unbalanced blade can cause vibration and damage to your mower.
  5. Reinstall the blade: Once the blade is sharpened and balanced, reinstall it on your mower. Make sure it’s securely fastened and the blade height is set to your desired level.

When to Replace a Blade:

While sharpening a blade can extend its lifespan, there are times when a replacement is necessary. Here are some signs that your blade may be beyond repair:

  • Severe Damage: If the blade has cracks, chips, or other severe damage, it should be replaced. These damaged areas can cause uneven cutting and pose a safety hazard.
  • Excessively Thin: After multiple sharpening sessions, the blade may become too thin. A thin blade can be more prone to breakage and may not provide a clean cut.
  • Wear and Tear: Even with proper care and sharpening, blades eventually wear out due to general wear and tear. If you find yourself sharpening your blade frequently, it’s time to consider a replacement.

Choosing the Right Replacement Blade

When it comes to choosing a replacement blade, several factors should be considered:

  • Mower Model: Always choose a blade that is specifically designed for your mower model. Different mowers have different blade shapes and sizes that are crucial for optimal performance.
  • Blade Material: Blades are made from various materials, each with its own advantages and disadvantages. Steel blades are typically the most common and affordable, while high-carbon steel and hardened steel offer greater durability.
  • Blade Height: The blade height determines the cut height of your grass. Make sure to choose a blade with the appropriate height for your desired cut.
  • Blade Pitch: The blade pitch refers to the angle of the cutting edge. A higher pitch results in a finer cut, while a lower pitch delivers a coarser cut. Choose the pitch that best suits your grass type and desired cutting style.


Choosing the right size and type of blade for your lawn mower is crucial for achieving a healthy, beautiful lawn. By understanding the factors that influence blade selection, knowing when to sharpen or replace your blade, and following the tips provided in this guide, you can ensure that your mower is always equipped to deliver a perfect cut. Remember, a well-maintained blade is essential for a vibrant, healthy lawn that will be the envy of your neighborhood.


Q1: How do I know what size blade to use for my lawn mower?

The blade size you need depends on the specific model of your lawnmower. Each manufacturer provides a recommended blade size for their machines, which you can find in the owner’s manual or on the manufacturer’s website. You can also look at the existing blade on your lawnmower to determine its size.

Always use the recommended blade size for your mower to ensure proper performance and prevent damage to your machine. Using a blade that’s too small can overload the engine, while a blade that’s too large can cause excessive vibration and damage to the deck.

Q2: Can I use a different size blade than the one recommended for my lawnmower?

While you can technically use a different size blade, it’s strongly discouraged. Using a non-recommended blade can negatively impact your lawn mower’s performance and potentially damage the engine or other components.

If you’re looking to improve your lawn mower’s cutting performance, consider upgrading to a mulching blade or a high-lift blade, but always stick to the recommended size for your specific model.

Q3: What happens if I use the wrong size blade?

Using a blade that’s too small can put a strain on the engine, leading to overheating, reduced power, and even damage to the motor. Conversely, a blade that’s too large can cause excessive vibration and wear on the mower deck, potentially leading to cracks or other structural issues.

It’s crucial to use the correct blade size to maintain optimal performance and extend the lifespan of your lawn mower.

Q4: What are the benefits of using the correct size blade?

Using the correct size blade for your lawn mower ensures optimal performance and longevity. The right blade size allows for proper airflow, efficient cutting, and prevents strain on the engine. This leads to a cleaner cut, better mulching, and a smoother mowing experience.

Additionally, using the right size blade prevents premature wear and tear on the mower deck and engine, ultimately extending the life of your machine.

Q5: How often should I replace my lawn mower blade?

The frequency of blade replacement depends on several factors, including mowing frequency, type of grass, and blade sharpness. Generally, you should replace your blade at least once a year, or more frequently if you notice dulling or damage.

A dull blade can tear the grass instead of cleanly cutting it, leading to a brown and uneven lawn. A damaged blade can create a rough cut and potentially even damage your lawn mower deck.

Q6: Can I sharpen my lawn mower blade instead of replacing it?

Yes, you can sharpen your lawn mower blade, and it’s a good way to extend its life. However, if the blade is severely damaged or worn, it’s better to replace it entirely.

Sharpening your blade can improve cutting performance and prevent tearing of the grass. You can sharpen the blade yourself using a file or take it to a professional for sharpening.

Q7: Where can I find replacement blades for my lawn mower?

Replacement blades are readily available at most hardware stores, online retailers, and authorized lawn mower dealers. When purchasing a new blade, make sure it’s the correct size and type for your specific lawn mower model.

Remember to always check the manufacturer’s recommendations for blade size and type to ensure optimal performance and safety.

Leave a Comment