Ridge Count Conversion

Index finger:

01 to 09 inner (I);

10+ outer (0)

Middle finger:

01 to 10 inner (I):

11+ outer (O)

Ring finger:

01 to 13 inner (I):

14+ outer (O)

Conversion Chart for Ridge Counts




1 to 9 inner (I)

1 to 13 inner (I)

1 to 10 inner (I)

10+ outer (O)

14+ outer (0)

11+ outer (0)

1 to 10 inner (I)

1 to 9 inner (I)

1 to 13 inner (I)

11+ outer (0)

10+ outer (0)

14+ outer (0)




Whorl ridge tracings are indicated by the value of the tracing:

  • (I) = Inner—3 or more ridges inside the right delta
  • (M) = Meet—0, 1, or 2 ridges inside or outside the right delta
  • (O) = Outer— 3 or more ridges outside the right delta

An example of how the conversion appears from the fingerprint card to the classification is:

Note: There is an additional division that may be utilized to further subdivide the fingerprint classification. The further subdivision is called the second subsecondary. This division has rarely been used for classification purposes. However, the division does exist and bears mentioning. As with the secondary, the second subsecondary has a conversion chart that differs from the subsecondary. Rather than burden the reader with additional information, I feel it only necessary to mention the division as an ancillary part of the classification system.

The Major division of the classification consists of the ridge count or ridge trace value of the thumbs, right hand over left hand. The designation on the card appears immediately to the left of the primary. (If there is an A or T in the thumbs, there will be no major classification. Remember if there is a small letter group in the secondary, the subsecondary and major are also dispensed with.)

Whorl trace values will be indicated by inner (I), meet (M), or outer (O).

Loop counts must be converted into small (S), medium (M), or large (L).

When deciding which value to assign the thumbs for a loop conversion, always count the left thumb first. Based on the ridge count of the left thumbprint, the right thumb designation can be determined based on the conversion chart.

  • • Left thumb conversion for ridge counts:
  • • 1 to 11 small (S), 12 to 16 medium (M), 17+ large (L)
  • • Right thumb:
  • • If the ridge count of the left thumb is 16 or less, the same conversion is used for the left and right thumbs
  • • If the ridge count of the left thumb is 17 or more, a larger conversion chart must be utilized: 1 to 17 small (S), 18 to 22 medium (M), 23+ large (L)

Where a whorl appears in the left thumbprint, the right thumb is converted as though the left thumb had a ridge count of smaller than 17. In other words, use the smaller conversion chart to apply to the right thumb.

To better understand the conversion process, the chart shown below indicates the conversions for the subsecondary and the major.

An example of the proper placement and conversion of the fingerprints into their respective places in the classification is shown below.

The remaining two divisions of the classification are the easiest to understand as there are no conversions to undergo. One simply observes the pattern and the ridge count and expresses that in the classification. As you may have noticed, both refer to ridge counts, which means the remaining divisions consist of loop patterns. If there are no loop patterns on the card, neither of these divisions will be noted. The divisions are the key and the final.

The Final consists of the ridge count of a loop appearing in the fingerprints of little fingers. In order of preference, the right little finger is examined first to see if there is a loop pattern. If there is no loop pattern in the right little finger, then the left little finger is examined. If neither the prints from the right nor the left little fingers possess a loop, there will be no final.

The final division may be placed above (numerator) the classification line if the loop appears in the right little finger. If the loop appears in the left little finger, the ridge count will be placed below (denominator) the classification line. The final cannot consist of both fingers; the final will consist of one or the other.

In large whorl sections, whorls can also be counted, but this is rare. However, if a whorl is chosen to be included, there are rules that must be adhered to. The following rules apply when using whorls as the final.

  • • If the whorl appears on the right hand, one counts from the left delta to the core.
  • • If the whorl appears on the left hand, one counts from the right delta to the core.
  • • If there are two cores, count from the delta to the core which is the fewest number of ridges away.
  • • If the pattern is a double loop, count from the delta to the core of the upright loop.
  • • If loops are horizontal, use the one nearest core.

The key consists of the count of the first loop appearing on the card excluding the little fingers. The little fingers are reserved for inclusion in the final. The designation for the key is always indicated above the line farthest to the left on the classification.

Below is an example of a fingerprint card and a complete classification of all the divisions of the modified Henry system with the FBI extension.

What happens if the prints one is taking are not clear and legible? What happens if the pattern cannot be determined or if there are temporary or permanent injuries to the person being fingerprinted. How does one deal with these issues? How does one classify these types of fingerprints? As with other aspects of the Henry system, provisions have been made for just such occasions. The following information addresses special issues related to fingerprints.

  • • Classification of Scarred Patterns
  • • When the following cannot be determined_Give

a. Pattern type and value_Class of opposite finger

b. Pattern only_ Pattern of opposite finger

with actual value and reference

c. Count or Trace value_Probable with reference

d. Opposite fingers scarred_Meet whorls

  • • Classification of Amputated Fingers
  • • Missing fingers_Class

a. One_Same as opposite with all references

b. Two or more_Same as opposite with no references

c. Opposite_Meet whorls

  • • Fingers missing at birth are treated as amputations
  • • If all ten fingers are missing M32 VMMM(meet whorls')
  • • If both hands are amputated, take footprints.
  • • FBI maintains footprint files.
  • • If there is a partially amputated tip, it is classed as it appears and is referenced to the opposite finger.
  • • Classification of Bandaged and Unprintable Fingers
  • • One lacking—All references—opposite fingers.
  • • Two or more—Opposite class with no references.
  • • Opposites—Meet whorls.
  • • If a pattern can be seen, it can be described.

“Ulnar loop of about 9 ridge count.”

• Make all possible attempts to print the individual when the injury is healed.

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