Understanding Knife Sharpening Angles: Degrees Per Side vs. Inclusive Angle"

Degrees Per Side and Inclusive Angle

When you sharpen your knife, you need to first select an angle. However, it can be confusing if you don't understand the terminology used to describe the angles. There are two main ways to describe an angle when sharpening a knife.

Degrees Per Side (dps)

Degrees per side (dps) is the more common way to describe the angle when sharpening your knife. We use dps almost exclusively at Sharpening Supplies. We use it for a few reasons. First, it actually describes the angle you hold your knife or tool when you're sharpening and therefore relates directly to the act of sharpening. Second, if you're using a jig, those settings or markings will almost exclusively relate to the degrees per side.

Inclusive Angle

The inclusive angle is important. The inclusive angle is ultimately what determines the cutting performance and durability of the edge. The inclusive angle is just the sum of the two sides. However, we feel that using the inclusive angle is confusing when it relates to sharpening. Using inclusive angle forces you to calculate your angle when you sharpen (even if the calculation is simple). It also doesn't fully describe how an edge needs to be sharpened. There are many edges that have a zero or close to zero side (some Japanese knives, chisels, plane irons), and by just stating the inclusive angle it doesn't clarify how an item is sharpened. When used in single bevel tools, the primary angle is stated without further clarification.

How We Describe Angles at Sharpening Supplies

When speaking with customers, we just use the term angle. We have seldom if ever had to clarify. When you're talking about sharpening, the standard use of degrees per side is just easy to understand and is therefore the assumed standard.