Advanced Calculator
Example Data Table
| Common Ancestor | n1 | n2 | FA | Contribution |
|---|---|---|---|---|
| Grandparent A | 2 | 2 | 0 | 0.03125 |
| Great Grandparent B | 3 | 3 | 0 | 0.0078125 |
| Ancestor C | 4 | 3 | 0.0625 | 0.00415039 |
Formula Used
The calculator uses the pedigree path formula:
F = Σ [(1/2)n1+n2+1 × (1 + FA)]
F is the coefficient of inbreeding. n1 is the number of generations from one parent to the common ancestor. n2 is the number of generations from the other parent to the same ancestor. FA is the inbreeding coefficient of that common ancestor.
Each common ancestor path creates one contribution. The final coefficient is the sum of all valid independent path contributions.
How to Use This Calculator
- Enter the subject name for your report.
- Add every common ancestor shared by both parents.
- Enter n1 and n2 generation counts for each path.
- Enter FA if the common ancestor is already inbred.
- Press Calculate to view the coefficient and risk level.
- Use CSV or PDF buttons to export your result.
Understanding Coefficient of Inbreeding
What the Value Means
The coefficient of inbreeding estimates the chance that two gene copies are identical by descent. It is often written as F. A value of 0 means no known inbreeding from the entered pedigree. A value of 0.0625 equals 6.25 percent. This can happen in some cousin level matings. A value of 0.25 equals 25 percent. This is commonly linked with very close relationships.
Why Pedigree Paths Matter
The calculator works by finding shared ancestors between both sides of a pedigree. Each shared ancestor creates a path. Shorter paths add more risk. Longer paths add less risk because the chance is divided by each generation. If a shared ancestor was already inbred, the contribution becomes larger.
Advanced Use Cases
Breeders can use this tool before planning a mating. It helps compare possible pairings with the same method. It can also support record reviews, pedigree audits, and genetic risk checks. The result should not replace genetic testing. It depends on complete pedigree information. Missing ancestors can make the final coefficient look lower than reality.
Reading Risk Levels
Low values usually show wider genetic distance. Moderate values may need closer review. High values deserve careful planning and expert advice. Very high values can increase the chance of inherited problems. Use the exported report to document assumptions, paths, and ancestor coefficients. Better records create better estimates.
FAQs
1. What is coefficient of inbreeding?
It estimates the chance that two gene copies came from the same ancestor. It is based on pedigree paths and shared ancestors.
2. What does n1 mean?
n1 is the number of generations from one parent back to the shared common ancestor in a valid pedigree path.
3. What does n2 mean?
n2 is the number of generations from the other parent back to the same common ancestor in that path.
4. Can I enter FA as a percent?
Yes. You may enter 0.125 or 12.5. Values above 1 are treated as percentages and converted automatically.
5. Why add multiple ancestor rows?
Each independent common ancestor path adds its own contribution. The final coefficient is the sum of all valid contributions.
6. Is this result a genetic test?
No. It is a pedigree estimate. Genetic testing can reveal information that pedigree records may miss or record incorrectly.
7. What is a high coefficient?
Values above 12.5 percent are often reviewed carefully. Values near 25 percent suggest very close ancestry.
8. Why does pedigree completeness matter?
Missing ancestors can hide shared paths. That can make the calculated coefficient lower than the real inherited risk.