Finding the ideal cutting edge angle for any knife means compromising between strength and sharpness. Wide grinds provide strong edges, but high sharpness is sacrificed. Thin grinds provide high sharpness, but a thin edge is more prone to damage. So, what’s the “Goldilocks” zone? That depends on your blade’s steel, shape, and purpose.
Table of Contents
- How to Measure a Knife’s Edge Angle
- Optimal Knife Angles by Blade Type
- Is There One Best “Do-It-All” Edge Angle?
- Edge Angle vs. Edge Retention
- Edge Angle vs. Sharpness
- Other Factors That Affect Sharpness
How to Measure a Knife’s Edge Angle
Most modern knives have two angles ground into their blades: A larger “primary bevel,” which forms the side of the blade below the spine, and a smaller “secondary bevel,” which forms the cutting edge itself. Some call the tip of the secondary bevel the “apex.”
The cutting edge’s angle is obtained by measuring the angular width of the secondary bevel on both sides of the blade, and dividing that value by two. For example, if a knife is advertised as having a 17-degree cutting edge, the total angular width of the secondary bevel is 34 degrees.
The easiest way to record any knife’s edge angle is with a digital protractor. Zero out the protractor with both legs aligned. Then slowly push the knife’s blade into the protector until both sides of the secondary bevel are flush with the insides of each leg of the tool. Record the measurement provided by the gauge, and divide it by two.
Some Blades Have a Single Bevel
Some blades are ground with a single bevel, like the “Scandinavian” grind. Instead of having primary and secondary bevels, there’s just one, tall cutting edge ground into the blade. Single-bevel blades tend to have wider edges. They’re made for heavy-duty tasks, like chopping and hacking.
Optimal Knife Angles by Blade Type
The edge angles recommended below are based on blade type, and that blade’s intended use. Generally, harder blades are intended for finer and sharper cuts, so they have thinner grinds. Softer blades are usually made for heavy-duty use and have wider grinds. In a good blade, steel hardness complements the edge angle and purpose.
Straight Razor: Less Than 10 Degrees
Most straight razors are sharpened to between 7 and 8 degrees. This extremely narrow edge angle complements the straight razors’s common hollow grind and high hardness. A cutting edge this narrow will likely chip if used for anything other than shaving.
Sushi and Filet Knives: 10 to 15 degrees
Quality filet and sushi knives tend to have very high hardness (61 HRC or higher), which favors a narrow edge. These blades are reserved for delicate slicing and filet cuts, where a fine edge is a necessity. Even in the kitchen, this angle is typically too fine for heavy chopping or striking against cutting boards. The blade may chip.
Japanese Kitchen Knives: 16 to 17 degrees
Japanese knives’ edges favor this angle for general kitchen duties. An edge angle of 16 to 17 degrees is capable of making delicate cuts with a lower risk of chipping when used for dicing.
Small Cutters, Pocket Knives: 18 to 22 degrees
A small blade that’s dedicated to cutting rope, rubber, or cardboard will hold up well and slice easily within this angle range. Many western kitchen knives also sport a blade angle on the lower end of this range, usually between 18 and 20 degrees.
Tactical Knives, Choppers, Field Knives: 23 to 30 degrees
Here, you begin trading real sharpness for high durability when stabbing and striking. These edge angles tend to favor softer, thicker steels found on large knives like Bowies, Ka-Bars, hatchets, combat and survival knives, and tactical fixed blades. At the higher end of this range (25 to 30 degrees) you can confidently chop firewood without risking edge damage.
Large Axes, Prying Blades, Striking Other Metals: 30+ Degrees
An edge measuring 30 degrees or more is reserved for extreme duty, like repeatedly chopping hardwoods or cutting through other, softer metals. Angles this wide are rarely ever found on conventional knife blades.
Is There One Best “Do-It-All” Edge Angle?
Yes. The optimal default knife edge angle for any general-purpose blade is 20 degrees. This is the angle you should use. This angle is also best if you want an edge that provides the best balance between sharpness and toughness.
To re-grind or maintain your knife’s edge, you’ll need some proper sharpening stones. Check out our comparison guide that covers all whetstones.
Edge Angle vs. Edge Retention
Edge angle doesn’t greatly affect edge retention. In other words, a narrower knife edge won’t dull much faster than a wide edge.
To test this, Knife Steel Nerds obtained a set of blades forged from 154CM (ingot) and CPM-154 (powdered metal) steel. The blades were sharpened with edge angles of 25 degrees, 17 degrees, and 10 degrees. Each edge was tested by cutting through 5% silica-impregnated cardstock 60 times at the same rate and force. The length of cardstock cut each time was measured in millimeters.
This graph shows the cumulative amount of cardstock cut with each blade, per pass.
On the 60th (final) cutting pass:
- The 25-degree edge cut 1.5mm of cardstock, compared to 23.1mm on the first pass. This is a 93.5% reduction.
- The 17-degree edge cut 1.8mm of cardstock, compared to 41.7mm on the first pass. This is a 95.7% reduction.
- The 10-degree edge cut 3.3mm of cardstock, compared to 71.4mm on the first pass. This is a 93.4% reduction.
The wider edges (25 and 17 degrees) lost their cutting ability only slightly slower than the 10-degree edge. But after 60 cutting attempts, each blade lost between 93% and 95% of its initial sharpness.
Remember that a 10-degree edge is extreme, reserved for straight razors and some filet knives. For typical knives with edges ground to between 17 and 25 degrees, sharpness is lost at a mostly linear rate. The idea that wider edges retain sharpness significantly longer than narrow edges is a myth. This reinforces that a 20-degree edge is a good default angle for any general-purpose knife.
Edge Angle vs. Sharpness
Angle plays the greatest role in determining sharpness. In the cardstock cutting test, the narrower blades had vastly greater cutting power. After all 60 cutting attempts were complete:
- The 25-degree edge cut 141.5mm of cardstock.
- The 17-degree edge cut 391.3mm of cardstock, 2.76 times more than the 25-degree edge.
- The 10-degree edge cut 1,007.1mm of cardstock, 7.11 times more than the 25-degree edge, and 2.57 more than the the 17-degree edge.
Ready to put the perfect edge on your knife? Learn how to sharpen with whetstones.
Other Factors That Affect Sharpness
Edge angle matters quite a lot, but other factors contribute to sharpness and cutting performance. Learn more about them below: