How to read a Histogram for Alpaca

Understanding OFDA 2000 Test Results Interpreting test results adds value to the decision to test. Here are some pointers that will enhance the raw data the test gives you:

  • Average Fiber Diameter- Often called AFD, this information is often over-valued in itself but, when combined with other results, gives breeders an idea of where their breeding program, in relation to fineness. is heading. The AFD is the average of all the measurements taken along the length of the fibers under test, unlike the butt sample test which measures at one point only. Micron variation within a staple is greater than the variation across a fleece, with a range of 8 to 12 micron not unusual, and as much as 15 micron in more primitive fleece samples.

  • Standard Deviation- The SD is a measurement of the number of fibers within a standard deviation of the mean. In other words, about 69% of all the fibers will be within the number of microns of the SD to the mean. For example, an SD of 4 micron on an AFD of 21 micron means that 69% of the fibers in the test fell within 4 micron either side of 21 micron. It follows then that the lower the SD the more uniform the sample for AFD and therefore the better the handle.

  • Coefficient of Variation- A mathematical calculation that reflects the uniformity of micron in the sample.

  • Comfort Factor- 100 less the percentage of fibers over 30 micron. The CF indicates the comfortableness of the fiber against the skin with a reading over 96 being an indication of the lack of prickle in yarn made from this sample.

  • Curvature- This is a sophisticated measurement mainly developed for the processing industry to evaluate amplitude (depth) of the crimp, with high numbers indicating deep crimp and low numbers indicating low crimp. For suri, the number is always low whilst for short, high frequency crimp huacaya the number gets higher the deeper the crimp is.

  • Fiber Length- The relaxed length of the test sample as it is tested.

  • Histogram- This is a graphic representation of the test results determining AFD, A narrow based and tall histogram indicates low SD, low CV and a highly desirable fleece. Breeders must make sure that, when comparing histograms, they check the scale of the axis to ensure that they are comparing like to like. As fleeces get finer, the histogram moves further to the left on the bottom axis and to the right as the fiber strengthens in micron.

  • Warning :     All fiber testing protocols have a margin of error of 1.2 micron on any one test. It is not possible to compare tests between different testing protocols with any confidence. We trust that you will find your OFDA 2000 test results to be of value to you and your breeding program - and if you have any questions or need additional information or interpretation, please feel free to call or email us.

We suggest following this link. Lots of resources here!!  Why reinvent the wheel? 

Alpaca Consulting USA

Descriptions of Terms:

  • Mean:  Average fiber diameter (micron)

  • SD:  Standard Deviation (fiber diameter variation in a sample)

  • CV:  Co-efficient of Variation (spread of fiber diameter variation throughout the fleece)

  • %>30: The percent of fibers over 30 micron

This is just one tool in the measurement of the fiber; also to be considered is the handle, the degree of softness displayed by the individual fleeces.


Some people prefer to have their fibers graded. Here is a Micron Grading Chart:

#1        RB     Royal Baby          under 20 microns         this is not fiber from a Baby Alpaca it is a classification 


#2        B        Baby                     20-22.9 microns           this is not fiber from a Baby Alpaca it is a classification

#3        SF      Super Fine           23.0 –25.9 microns

#4        M       Medium               26.0 – 28.9 microns

#5        C         Coarse                29.0 – 32.0 microns

#6        S         Super Coarse     32.0 – 35.0 microns