Knife Sharpening: Coin Trick & Magic Angle Finder

Here’s a quick Technique of the Week to get us started. You often read that you should sharpen your knife to 20° or 15° or some other seemingly arbitrary number. If you have a standard European-style (German, French or something along those lines) chef’s knife, it probably has edge angles of 20-25° per side. A western-style Japanese chef’s knife (Shun, Mac, Global, et at) will have edge angles about 15-16° per side. The trick is being able to find and repeat those angles. That’s where the Magic Angle Finder comes in. I won’t go into the math, but you can divide the height of the blade (at the heel) by a specific number to find out how high to raise the spine above the sharpening stone for a given angle. It sounds more complicated than it really is. Here’s how it works:

Chad’s Magic Angle Finder

For 20° divide by 3
For 15° divide by 4
For 12° divide by 5
For 10° divide by 6
For 8° divide by 7

So, if your chef’s knife is 1.5 inches tall, measured from spine to edge, and you want to put a 20° edge on it, just divide 1.5 by 3 to get .5 inches. Lay the knife flat on the stone and then raise the spine .5 inches. You have just set the edge angle at 20°. It works in metric, too. If you want to put a racy 12° edge angle on your Japanese gyuto and it is 45mm wide at the heel, just divide 45 by 5 to get 9. Raise the spine to 9mm above the stone and you are good to go. It can be a little tedious to sit there with a ruler, checking to make sure you’re at the right height but the payoff in consistency is well worth it. It also helps ingrain the angles into muscle memory so that the next time is much easier.

Coin Tricks

If that is too nerdy for you, you can just use a stack of quarters. A US quarter coin is officially .069 inches thick, though they vary slightly. Four quarters is a little more than .25″, five quarters is about .33″, six quarters is about .4″, 7 quarters is just under .5″ and eight quarters is just over .5″. It takes a surprising 15 quarters to reach a full inch high.

To raise the spine of your chef’s knife .5″, use 7 quarters. It’s not quite .5″ but the width of the spine makes up the difference and puts the spine at almost exactly the right height.

Join the Conversation


  1. I own several Shun knives and the manufacture recommended angle to sharpen and hone is at 20 degrees…..Just thought you might like to know that for future reference.

    P.S. i do infact sharpen mine at 15 degrees and usually hone at about the same angle.

  2. Correction on the Shun sharpening angle, according to their web site:

    Correction to Chef Tim on the Shun sharpening angle. Chad got it right in the article, though. According to their web site:

    “Shun knives are sharpened to a 16° angle on either side.”

    And if you can be without it for up to four weeks, they’ll sharpen it and send it back to you for free (that also goes for warrantee service). You have to get it to them on your dime, though.


  3. If you are the guy who wrote a 2003 article, Knife Maintenance and Sharpening, on eG Forum, I am impressed. You must be very smart, because you stated some things I was thinking, but no one seemed to believe. (Just kidding, but I did feel less stupid.)

    I just could not get a sharp edge. Now, I am optimistic. My cutting is 95% skinning, gutting, and a little boning. It has always seemed that a burred edge worked best. Does that make sense?

    It never occurred to me to make the two angles in the edge.

    Question: for my uses: gutting and skinning, which angles are best?

    BTW, my Father could do the fancy steel thing, but he drew the edge away from the steel, in a strpping fashion. He said it was safer, and drew out the burrs.

    Last question? Do you recommend, when using a Lansky, to sharpen part of the blade, then move the blade down in the clamp, to avoid rounding the edge?

    Thanks. Riecke

  4. Excellent. Exactly the information I have been looking for. I’ve been going by the feel of the knife on the stone (Japanese knives) and I was happy to see that my freehand angle is pretty darn close to 15 degrees, using this angle measuring method. I was thinking of using maybe a deck of playing cards to get the height. So many cards = 9mm, so many cards = 10mm, etc. I think I’ll stack up a bunch until it is 1 cm tall and then count them and divide by ten to get how many cards per millimeter, and use that instead of coins to get different heights.

    Thanks for doing this great web page.

  5. I make knives from farrier files as a hobby and sharpen knives to defray some cost. I use templates with cutout V shapes of included angles, I drop the blade into the selected angle template, centralise both sides and note the gap between spine and template. This method works well because it negates the profile of the blade thickness and shape, sabre, hollow, convex, as you are using the blade centreline to establish the edge angle in relation to it. Just another way to arrive at the same place !.
    Your formula is very handy when away from home and templates.

  6. Loved your book, tried the mousepad trick, then tried the variation where the base is 1/4″ thick leather instead of a mouse pad and the results are even better. You should include that in your next update of your book.

  7. HI Chad,

    Found your website after reading Russ Parson’s article on knives from the LA Times. I own a 8″ Mizuno chef knife and I am looking into figuring out how to properly sharpen my knife without ruining it.

    Have you ever heard of this sharpening tool called Edge Pro? Here is their web link so you can see how it looks and how it is used.

    Just curious if you would recommend something like this to sharpen your knives instead of trying to figure out how to use stones.

    Thanks for you time in responding to my question.


  8. Hi George, the EdgePro is an excellent tool. I have one and use it when I have a pile of knives to sharpen and don’t feel like taking the time to freehand. Ben Dale & company have made one of the best guided sharpening systems out there, and if you don’t mind the price it will serve you for the rest of your life. Customer service is top notch, too. In short, the EdgePro is highly recommended.

    Best of luck,

  9. Hi Chad, apologies for this reply as I saw the original post was a while back. I own Henckels and Shun knives and looking to get a sharpening tool to properly sharpen them at home. I’ve read many great reviews about electric sharpening tool Chef’s Choice 1520 and 130. I just saw the comment about the EdgePro too. Now I am undecided in my research, whether electric or manual. Would love to hear your recommendations. Many thanks for your response.

    — Kim

  10. Hi Chad, I stumbled upon this post while researching knife sharpeners for my set of Shun and Henckels. I was about to make the move on the electric knife sharpener ChefsChoice M130 Electric Knife Sharpener which received excellent reviews. Then I saw in the comments about the EdgePro. What are the pros and cons of an electric vs hand sharpening? What would you recommend?

    Thank you for your response.

    — Kim

  11. Hi, Kim, sorry for the slow reply. I’ve been doing a lot of other writing and haven’t had the chance to check my blog as often as I should.

    I’m generally not a big fan of electric sharpeners. They can remove a lot of metal in a hurry. With that said, the Chef’s Choice sharpeners are the best out there. However, they should come with a big red warning label and a system that won’t turn the sharpener on until the new owner has read the manual — twice. The biggest problem with electric sharpeners is with Stage 1, which really shouldn’t be used unless a knife has been used to chop cinder blocks or been beaten on the sidewalk for a while. The trick to using an electric sharpener is to use it backwards. Use Stage 3, the finest stage, the keep the edge touched up and ready to go. When that stops working, go to Stage 2 to refresh the edge, then refine it on Stage 3. Going back to Stage 2 should happen about once a year in an average household. Only go to Stage 1 in an emergency, and even then use it sparingly. Electric sharpeners can only set one angle on your knives, usually one that leaves the edge too thick.

    The EdgePro Apex is a manual system that is infinitely variable, meaning that you can set just about any edge angle you want. The EdgePro also will create much finer, much sharper, edges than an electric sharpener. The downside is that it is more expensive, takes more time to use, and has a learning curve before you really master it.

    A third option is professional sharpening. Not the guy down at Sur la Table or Joanne’s Fabrics, but a real professional at a cutlery shop or someone who does mail order sharpening. If you don’t mind being without your knives for a couple of days, somebody like Dave Martell at D&R Sharpening can do a remarkable job.

    In my opinion, if you own a lot of knives that you need to keep touched up, an electric sharpener is okay. If you have fewer, higher end, knives and don’t mind spending time and money to fuss over them, the EdgePro Apex is a great choice. If you love your knives but they are primarily tools, try professional sharpening and see what you think. It could very well be that sending them out once or twice a year is all you need to keep them in top shape.

  12. “Heighth of the blade at the heel” does this mean how wide my blade is? Where exactly do I measure? How many quarters would be used for a knife blade that is an inch wide?

  13. I do not understand the math behind the quarter trick. Im wanting to put a 20 degree angle. How many quarters for a knife with a blade that is an inch wide?

  14. Hi Lorraine, as mentioned in the Magic Angle Finder section, to get a 20 degree angle, divide the blade width by 3. If your knife is 1″ wide from spine to heel (the back corner of the knife nearest the handle) that means you need to raise the spine .33 inches above the stone. That’s right about 5 quarters in height.

    Thanks for your question!

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