How to Test Knife’s Edge Sharpness

How to Test Knife’s Edge Sharpness? [6 Different Processes]

(Last Updated On: July 8, 2021)

Not every knife user can tell if a knife is sharp. Many think if the knife can cut food, then it is sharp. However, this is not how you measure the sharpness of a knife. Hence, all knife users need to know how to test the sharpness of a knife’s edge.

However, a knife’s sharpness depends on the type of knife. Different types of knives come with different sharpness measurements. It also depends on the production method and quality. Many German and Japanese popular and well-known knife brands produce quality knives but the sharpness inevitably varies. 

With constant use, a knife loses its sharpness so it requires sharpening. Again, a dull knife can also cut fruits or veggies, but it requires effort and force, whereas a truly sharp knife can easily and effortlessly cut.

 But, the question arises, how would you measure the knife’s sharpness? Well, there are several ways to answer the question, how to measure a knife’s sharpness. Read till the end to know them.

How to Test Knife’s Edge Sharpness [Step by Step Measuring Sharpness]

To determine the knife sharpness there are many ways. The sharpening of the knife can be done using many techniques and methods depending on the blade material. However, without making any delay let’s get to the main points.

1. Sharpness measurement through Paper Test

If you want to go for the most common and vastly tiring method for measuring the knife sharpness then call for the paper test. This specific method is hugely tried worldwide and considered one of the truest old methods for measuring sharpness. Now, to experiment on this test, you have to grab one tool to know the method.

The Process of Paper Test for Measuring a Knife’s Sharpness  

Step 1: First of all, fetch a piece of paper from anywhere then hold it with your fingers. Now, slide the knife straightly to the downward of the knife. If the paper gets sliced easily and cleanly without being rugged then the knife is sharp. 

Step 2: The sharp knife will cut through the paper absolutely effortlessly. Only the weight of the knife on the paper will slice the paper if it is really sharp. If it is not, then there will be seen ragged edges of the paper. Again, the dull knife will slip right off the paper while slicing.

Paper Test Result of How to Test Knife’s Edge Sharpness  

 Only a single stroke would be enough to get through the paper. However, make sure the paper is slick and thin. It is better if you find a magazine paper for this purpose. With the paper, you can actually have the right experiment because this type of paper is hard to slice for a knife.

 However, you can try the test with many other types of papers including tissue paper, phone book paper, and all. Using a phone book paper for this test is a tougher option but, using tissue paper is the toughest. If your knife manages to slice through the tissue paper with a single stroke without any slippery or ragging then you have the sharpest knife ever.

An alternative to Paper Test 

There is another method for this test. Make the paper have a rounded edge by folding it in half. Put the knife on the top of the rounded edge of the paper and then start slicing it. This is how you can identify the sharpness of your knife.

2. Measure it with the ‘Tomato Test’

Many knife users own a kitchen knife which is why the tomato test is suitable for them. The tomato test is like the paper test but as the materials are not the same there are some differences.

The Process of Tomato Test for Measuring a Knife’s Sharpness  

Step 1: For this test, you will have to grab a tomato obviously! Now, tomatoes have tough skin but the inside of the fruit is soft. Hence, the sharpness will be measured determining how effortlessly the knife goes through the tomato.

Step 2: The riper is the tomato, the harder to slide through. Now, put the tomato on a chopping board and start slicing it without putting any pressure. If the knife is sharp it will slide through the fruit with zero downward pressure. 

This test is done with tomato because while cutting other edibles you may not feel the dullness of your knife but when you try to cut a tomato you will easily feel the dullness. However, a dull knife will certainly not succeed to go through the tomato rather it will end up smashing the fruit.

Tomato Test Result of Sharpness 

The tomato will get crushed if it is tested with a dull knife. But a sharp knife will deliver a perfect slice whereas you just have to hold the knife over the tomato. It will easily strike through the rough and tough skin of the fruit and will also give a sharp cut of the softer fleshy portion.

So, now you can assume how easy the experiment is. This is also an old and easy method of testing a knife’s sharpness.

3. Ever tried the ‘Hair whittling Test’!

This hair whittling test is for those who use some of the advanced knives. These knife users are also advanced because they can try on this hair whittling test. This is an unbelievable test but if your knife can score the test then most probably you have the sharpest knife in your hand. This is the toughest test ever and you will find it hard to get the knife to have a touch of the hair while whittling it.

The Process of Hair Whittling Test for Measuring a Knife’s Sharpness

Step 1: For this test, you need hair. Yes, that’s kinda weird as well but actually, you need a hair for this test. Long hair is highly suggested for this test because with short hair the test will be tougher. Fortunately, the sharp knife will split through the knife both vertically and horizontally.

Hair Whittling Test Result of Sharpness

If your knife is capable of whittling the hair for some minutes then know that your knife is made of the best blade material and with the sharpest edge and superior edge retention. This test is quite impressive and can be done with a different type of small knives or hunting knives.

4. ‘Three Finger Test’ for the skilled Bladesmith

This test is recognized by the master Bladesmith named Murray Carter. First of all, this test is not for everybody. It is only suggested to the skilled smiths out there. This test demands carefulness, knowledge, and most practices. The tester has to run his fingers along the sharp edge of the blade. For this test three fingers are used hence, the test is called the three-finger test.

The Process of Three Finger Test for Measuring a Knife’s Sharpness 

Step 1: For this test, the experimenter first needs to put his thumbnail on the opposite side of the sharpened edge of the knife. Then, he has to put his next three fingers on the sharpened edge. He has to apply very light pressure on the blade edge carefully. 

Step 2: This way he can feel the sharpness of the blade. He has to make sure he doesn’t back and forth the knife while doing the test otherwise, he may end up having a bad bite from the knife. Now, if the knife is sharp enough it will send signals to your finger nerves and you will know it for sure.

Three Finger Test Result of Sharpness 

However, if the knife is dull then you will feel the dullness as it won’t feel anything when you put much pressure on it. Whereas the sharp knife catches the back and forth of the fingers and makes the fingers stop, the dull knife allows the fingers to have constant back and forth movement. 

5. ‘Fingernail Test’ also Works! 

 If you are brave enough you can go for the fingernail test. Our fingernail is covered with alpha-keratin which is protective and also hard enough to do this test. This is a nice trick for measuring the knife sharpness.

The Process of Fingernail Test for Measuring a Knife’s Sharpness 

Step 1:  Your nails have some calcium on them. You can test the sharpness of the knife by shaving off the nail calcium. A sharp knife will easily shave it off whereas the dull one will make the shaving a mess. 

Step 2: However, the main method of this fingernail test is that you have to put the sharp edge of the knife on the fingernail. Thumbnails will work great for this test.You are not supposed to put any pressure into the thumbnail.

Fingernail Test Result of Sharpness 

However, if the blade is sharp enough it will catch along the nail and won’t move. But, if the blade is dull it will slide around without catching the nail.

6. ‘Tongue Test’ for having the most terrific test!

This is probably the most hilarious test for measuring any knife’s sharpness which is not recommended by us at all! But you will see many videos roaming around Youtube about people doing the tongue test for determining knife sharpness.

This idea of measuring the sharpness is crazy and not everyone is ready to do this stunt. Hence, do not try this for god’s sake at home. 

However, these are some of the processes or ways of measuring the sharpness of any knives. There are many other knives like visual inspection, shaving test, and all. 


So, we have shown some of the ways you can try to test the sharpness of your owned knives. Maintaining the sharpness of the knives is very important. Many expensive knives go fail because the user cannot maintain the sharpness of the knives and they get easily dull. However, for the easy tests, you can easily go for the paper test and tomato test.

Both the test will be effective to measure the blade sharpness. Now, let us know which knife sharpness test has convinced you more and why.   


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