There have been one too many times where people have been confused by FP numbers using them as offset and saying that Japanese irons like the r7 Forged have "reverse offset (more offset in shorter than longer irons)" or other JDM irons have humongous offset. This is NOT the case.

To make things simple FP is a different measurement that can be used to calculate offset. The higher the FP number the less offset there is.

I've used the Epon AF-701 to illustrate.

Face progression measures how far forward (or behind as there can be negative FP) the leading edge is from the centerline axis of the shaft.

Offset on the other hand uses the leading edge in relation to the most forward part of the hosel. When we think offset, it's usually the forward part of the hosel in FRONT of the leading edge.

Another part of the confusion is that offset is measured typically in inches while face progression is almost always in millimeters. Yes it can be hard to compute in two different dimensions. (^_^)

Even though it doesn't seem like it, in fact the larger the FP number, the smaller the offset.

The key number to know is what the hosel diameter is (typical irons are around 13.6mm or 0.535" but that number mostly varies which adds to the confusion).

Using Face Progression to calculate, here are the offset numbers for the AF-701.

Offset is calculated by taking half the hosel diameter, the AF-701 has a 13.5mm hosel (13.5mm / 2 = 6.75) minus the FP and divided by 25.4 to convert mm to inches.

4 Iron Example: (6.75-1.55)=5.2, 5.2/25.4= 0.205"

So hopefully this clears things up a bit... when you're looking at those Epon AF-301's and the FP numbers are getting larger, it does not mean the offset is more in the shorter irons!

One thing learning this calculation did show me though was that the AF-501 shorter irons have LESS offset than the AF-301 short irons!

Hope that all made sense and helps a bit the next time you look at FP numbers.

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