Genealogy Numbering Systems (National Institute)

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The original content for this article was contributed by The National Institute for Genealogical Studies in June 2012. It is an excerpt from their course Methodology - Part 1: Getting Started, Methodology - Part 2: Organizing and Skillbuilding, Methodology - Part 3: More Strategies, Methodology - Part 4: Effective Searching and Recording, Methodology - Part 5: How To Prove It, and Methodology - Part 6: Professional Preparation and Practice  by Louise St Denis, Brenda Dougall Merriman and Dr. Penelope Christensen. The Institute offers over 200 comprehensive genealogy courses for a fee ($).

Reference Numbers[edit | edit source]

A reference number, or an identification number, for all individuals will make it much easier for you to find the person you are looking for. Again you must be consistent.

Ancestral Reference Numbering System[edit | edit source]

Let’s start with ancestors, since the number of ancestors are easily identified. A logical pattern follows. We all have:

  2   1 mother and 1 father
  4 grandparents
  8    great-grandparents
16 2nd great-grandparents
32 3rd great-grandparents
64 4th great-grandparents ===================
etc., etc.

Each generation doubles in size. Start with yourself in the first generation. Then your parents, and so on:

2nd generation
2 ancestors
= 2 ancestors in total
3rd generation
4 ancestors
= 6 ancestors in total
4th generation
8 ancestors
= 14 ancestors in total
5th generation
16 ancestors
= 30 ancestors in total
6th generation
32 ancestors
= 62 ancestors in total
7th generation
64 ancestors
= 126 ancestors in total
8th generation
128 ancestors
= 254 ancestors in total
9th generation
256 ancestors
= 510 ancestors in total
10th generation
512 ancestors
= 1022 ancestors in total

The 10th generation by itself, will contain 512 ancestors. But a 10 generation list of ancestors contains 1,022 because this is the total number of ancestors for the 2nd to the 10th generation inclusive.

Ancestors are traditionally recorded on a PEDIGREE CHART. Here is a description of the most commonly used coding system on Pedigree Charts.

This chart will list all your ancestors from one father and mother to the next father and mother. The reference person number 1, will be the person whose genealogy you are doing. If you are researching your entire genealogy, then your name will be reference number 1. The numbering sequence on your pedigree chart will be as follows:

1 You
2 Your father
3 Your mother
4 Your paternal grandfather
5 Your paternal grandmother
6 Your maternal grandfather
7 Your maternal grandmother
8 to 11 Your paternal great-grandparents
12 to 15 Your maternal great-grandparents
16 to 23 Your paternal 2nd great-grandparents
24 to 31 Your maternal 2nd great-grandparents

Notice that all male ancestors are even numbers and female ancestors are odd numbers. Mothers will always have their husband’s number plus 1.

If you use the sample chart found in your course material, you will notice that only 5 generations can be listed on a standard “8½ x 11” sheet, in other words 30 ancestors. These are pre-numbered 2 to 31.

Once you complete this chart, you start a new un-numbered chart. Where the number 1 appears on the numbered chart, you would indicate the reference number of the ancestor in the 5th generation (16 to 31). To calculate the reference number for the father of this ancestor, simply double the ancestor’s reference number. Continue the doubling method for each subsequent father.

An example:

  • Ancestor #22 in the 5th generation is now transferred to a new form.
  • The reference number for the father of ancestor #22 is #44.
  • The reference number for the grandfather of ancestor #22 is #88.
  • The reference number for the great-grandfather of ancestor #22 is #176.
  • Notice that for each generation, the reference number doubles for the next father.

During your research you will be using many other forms. When using the reference number on subsequent forms add PC to the code originated from the Pedigree Charts. Your paternal grandmother would be acknowledged by using the reference number PC5.

Descendants Reference Numbering System[edit | edit source]

When you start looking at individual family branches, the pattern for each family is different. One family might have 3 children while another family might have 10 children. Some of the children will be married while others will be single.

Before you can establish a logical coding system for your family branches, decide what you want to achieve. A pedigree chart is an ascending form starting with yourself, and only notes direct ancestors. A descendancy chart starts with a certain ancestral couple and comes “down” to you and living generations, including all children of all children. There are many variations on such charts.

Example[edit | edit source]

Here’s an example... If you wish to follow the family branches of your great-grandparents to include all your living relatives, here is the appropriate numbering sequence.

Each great-grandparents’ family is assigned an alphabetical code. Use the first letter of their surname, if they are all different. I like using the first letter of the surname because this prevents having to look up a reference number to know which family group you are referencing. Fewer errors will occur.

Following the first letter of the surname, indicate their Pedigree Chart reference number. For simplicity, only add the Pedigree Chart reference number to the first code for the family and not to each of the subsequent descendant’s reference numbers.

My paternal grandfather’s parents: SPC8/PC9.

  • S    — St Denis
  • PC  — Pedigree Chart
  • 8 — my paternal grandfather’s father
  • 9     — my paternal grandfather’s mother

The code ‘S’ is then used to signify all descendants of my paternal grandfather’s parents—St Denis.

Each of their children, preferably listed in chronological order, are numbered 1, 2, 3, 4, etc. So the fourth child of my great-grandparents (could be my grandparent or great uncle or great aunt) will have the code ‘S+4’. The plus sign (+) signifies a progression to the next generation.

Each child of the children of my great-grandparents are also numbered 1, 2, 3, 4, etc. So the third child of the fourth child of my great-grandparents will have the code ‘S+4+3’. Continue this same numbering sequence for all generations listed in the Family Group Record forms.


My great-grandparents
Last name St Denis
My grandfather
4th child of my great-grandparents
My father
3rd child of my grandparents
2nd child of my parents
My son
my 1st child

You can quickly see by this example that my son’s code, S+4+3+2+1, places him in the 5th generation down from my great-grandparents and he is also the oldest child.

It is preferable that the children of all couples be listed chronologically. This permits you to determine by the coding system the order of children of the couple. Should you make an error, after the coding is in place, you may wish to correct the coding, but this would require a lot of attention since all subsequent codes would also be affected as well as all references to that particular code. It is not advisable to code your family members until you feel fairly certain that the chronological order is correct.

You will run into one small problem in this coding system. Your grandparents will appear in two family groups. My grandfather St Denis married my grandmother D’Aoust. The reference code for my great-grandparents St Denis will start with S. The reference code for my great-grandparents D’Aoust will start with D.

At one point my grandfather will be listed with a reference number of S+6 and my grandmother will be listed with a reference number of D+8. The next reference number will be their children. At this point, I would suggest that you simply cross-reference the female spouse to the male spouse for all remaining information.

In this example, all descendants of my D’Aoust grandmother will start with the reference code ‘S’ assigned from my St Denis grandfather. Make sure the female ancestor’s form shows a clear cross-reference to the male ancestor to prevent confusion later on.

Do not try to repeat the information for duplicated families that are joined by marriage. Trying to duplicate the information will only create errors and confusion.

If you are using a computer to store your information, you may wish to adapt the coding system of your particular software to the Family Group Record forms.

This example is but one method of coding. I found this system very easy to use. I also found the coding system not only provided a reference number, but it also was informative in providing the chronological position within the family.

Ask three or four genealogists how they code ancestors’ descendants, you will probably observe different methods. Choose one you feel comfortable with and be consistent in using that method.

When using the reference number on subsequent forms, add FG to the code originated on the Family Group Record forms. We will discuss the form later, but suffice to say that this will be where you will initially list all descendants.

Major Numbering Systems[edit | edit source]

The generally accepted systems in North America for numbering descendants are either the “Register method” or the “NGSQ” method. Examples of these are continually featured in The New England Historical and Genealogical Register and the National Genealogical Society Quarterly — flagship journals for self-education through the study of their scholarly articles. More information about the two societies which produce these journals can be found at their websites.

The best reference guide explains both systems:

  • Curran, Joan Ferris, Madilyn Coen Crane, and John H. Wray. Numbering Your Genealogy: Basic Systems, Complex Families and International Kin. Arlington, VA, National Genealogical Society, 2000.


Information in this Wiki page is excerpted from the online courses Methodology - Part 1: Getting Started, Methodology - Part 2: Organizing and Skillbuilding, Methodology - Part 3: More Strategies, Methodology - Part 4: Effective Searching and Recording, Methodology - Part 5: How To Prove It, and Methodology - Part 6: Professional Preparation and Practice offered by The National Institute for Genealogical Studies. To learn more about these courses or other courses available from the Institute, see our website. We can be contacted at

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