Does Cutting Cardboard Sharpen a Knife?

By Ryan Leavitt •  Updated: 05/06/21 •  4 min read

Almost everyone knows of the fun fact that you can sharpen a knife by cutting through cardboard.

While most blades are designed to retain their edges for long, they also become dull with time.

So, when these edges become blunt, the ultimate thing to do is sharpen them.

You can invest in a sharpener or resort to DIY tricks such as cardboard to sharpen your blade.

So, does cutting cardboard sharpen a knife?

The short answer to this question is yes.  Cardboard works like a leather strap when it comes to stropping a blade to restore its edge. With cardboard, you have to cut at an angle so that the surface of the board grinds the edge.

Related: Knife sharpener types you should know about

Does cutting cardboard damage or dull a knife?

Cardboard just like other paper products requires you to be careful when cutting so that you do not dull or damage the cutting edge.

Cardboard is made from recycled materials and is thick and heavy.

Therefore, slicing through this board can potentially dull a thin blade as the knife will need thicker material than it would when slicing thinner paper.

Overall, cardboard is not the best material for sharpening your blade as it can potentially damage the knife.

This is especially if you cut through the cardboard regularly when restoring the cutting edge.

Which factors determine how a paper will impact a blade?

While cutting through paper with a blade can sharpen the edge, it can also have a negative impact and dull the knife.

There are a few factors that affect how the paper will impact the edge.

Some of these factors include:


The paper’s thickness determines the ease with which the blade will cut through the paper.

Thick papers contain larger filler particles and other materials that make it hard for the blade to slide through.

On the other hand, thinner paper is less harmful to the edge.

This is because the paper is soft thereby making it perfect for sharpening blades.

Consequently, the thin paper will dull the knife slower than thick paper.


Thick paper is dense due to the high content of fillers and added materials.

As such, heavy paper will make your blade dull.

Therefore, heavy paper may not be the best choice for sharpening your knife.

Ideally, the denser and thicker the paper is, the more it is likely to potentially harm and dull your blade.

Top everyday objects you can rely on for sharpening a knife

You do not necessarily need to have an electric sharpener or a sharpening steel rod to restore the edge of your blade.

This is because there is a wide variety of objects in the kitchen that you can use for honing and straightening the cutting edge of your blade.

Some of these objects are such as:

Coffee mug

It is common to find ceramic coffee mugs in most households.

These cups are perfect for straightening the edge of your blade.

All you need to do is to turn the cup upside down and run the edge across the rough part of the base.

Sharpen one side until it is finely finished and then turn to the other side.


While sandpaper is not an object you are likely to find in the kitchen, it comes in handy for sharpening your knife.

Use the coarse grit to sharpen and finish the edge with the fine grit for maximum sharpness.

Be careful when using sandpaper to sharpen your blades due to the risk of cutting your fingers.

Nail file

A nail file is a perfect alternative to sandpaper.

Both objects are used in a similar way when it comes to sharpening your blade.

Run the blade’s edge against the emery of the nail file.

Maintain the best sharpening angle for uniform and consistent sharpness.

A nail file is an excellent choice for polishing your blade before use if you do not have a honing rod.

What makes a blade dull?

The primary reason why blades become dull is due to repetitive use.

Also, wrong handling and use of the blade can also make it blunt.

For instance, if you use a kitchen blade for cutting through frozen and hard foods.

Washing the knife in a dishwasher can also potentially make the cutting edge dull.

Always take the best care of your knife for it to last longer and retain its edge for long.


In a pinch, cutting cardboard can sharpen your blade but only if done carefully and with precision.

There are lots of other safer and more efficient sharpening options that you can use for restoring the edge of your blade.

Always hone your knife after every few days to straighten its edge and prolong its sharpness.

Ryan Leavitt

Hi my name is Ryan Leavitt a Marine Corps Veteran and currently an over the road trucker (Long Haul). I am no expert chef but am enjoying preparing my own meals on the road and testing all the different knives.