Convert shared DNA percentage to centiMorgans (cM) or shared cM to DNA percentage using the testing-company baseline selected. Built for shared DNA between two people, with estimate-only relationship context.
Source: Relationship estimates are based on the Shared cM Project v4. They are theoretical possibilities, not exact biological certainties.
This tool converts shared DNA percentage to centiMorgans (cM) and converts shared cM back to shared DNA percentage for the same two-person comparison. It works in both directions: enter a percentage to get cM, or enter cM to get percentage. The conversion uses a baseline total cM value that you select based on your testing company.
This calculator is for shared DNA between two people only. It does not calculate GC content, nucleotide composition, or DNA base percentages used in biology or medical genetics. Relationship estimates appear after conversion but are secondary context, not the primary output.
What this calculator converts
You can enter shared DNA as a percentage and receive the equivalent in centiMorgans, or you can enter shared cM and receive the equivalent percentage. Both paths use the same baseline value in reverse calculations.
The result depends on the testing-company baseline you select. Each company uses a different total autosomal cM value as their reference point for 100% shared DNA.
The same percentage maps to different cM values depending on baseline. For example, 25% shared DNA equals 1860 cM on 23andMe but 1746.5 cM on AncestryDNA. The same cM value also maps to different percentages across baselines.
Baseline selection is part of the actual conversion logic, not just a display option.
DNA percentage to cM and cM to percentage formula
Percentage to cM:
cM = (percentage / 100) × base cMcM to percentage:
percentage = (shared cM / base cM) × 100Variables:
percentage= shared DNA percentage between two peoplecM= shared centiMorgans between two peoplebase cM= total autosomal cM baseline for the selected testing company
Changing the baseline changes the result because the baseline represents the denominator in both formulas. A larger baseline produces larger cM outputs for the same percentage, and smaller percentage outputs for the same cM.
The math is exact relative to the selected baseline. Cross-company interpretation remains approximate because different companies measure and report cM differently.
Testing company baselines used in this calculator
| Testing company | Total cM baseline |
|---|---|
| 23andMe | 7440 |
| AncestryDNA | 6986 |
| FamilyTreeDNA / MyHeritage | 7050 |
| Generic / Standard | 7000 |
The baseline represents the total autosomal cM value that the tool treats as 100% shared DNA for conversion purposes. This is the reference point all percentage calculations use.
Use the matching company baseline when you know which testing company generated your shared cM value. This keeps your conversion consistent with the source data.
Use the Generic option when you do not know the testing company, when comparing results across multiple companies, or when working with third-party tools that use a standard reference.
Generic is a fallback reference, not a universal standard. No single baseline applies to all testing companies or all interpretation frameworks.
| Shared DNA % | 23andMe (7440) | AncestryDNA (6986) | FamilyTreeDNA / MyHeritage (7050) | Generic (7000) |
|---|---|---|---|---|
| 1% | 74.4 | 69.86 | 70.5 | 70 |
| 5% | 372 | 349.3 | 352.5 | 350 |
| 10% | 744 | 698.6 | 705 | 700 |
| 25% | 1860 | 1746.5 | 1762.5 | 1750 |
| 50% | 3720 | 3493 | 3525 | 3500 |
The percentage remains constant across all columns while cM shifts with the selected baseline. Higher baselines produce higher cM values for the same percentage.
This table is useful for quick comparisons when you need to estimate how your shared DNA value would translate across different testing company baselines without running separate conversions.
How to read the relationship estimate
Relationship output appears after the tool completes your conversion or after you enter shared cM directly. The estimate uses your converted or entered cM value only.
Multiple relationship categories may appear because shared DNA ranges overlap between relationship types. For example, the cM range for half-siblings overlaps with the range for grandparent-grandchild.
Overlapping ranges are normal. The tool displays all categories that include your cM value within their published ranges. It does not rank, score, or confirm any relationship.
This output should be used as rough context only. The converter does not validate relationships, account for endogamy, adjust for segment quality, or incorporate family tree data. Treat relationship estimates as possible categories, not confirmed matches.
Input limits and assumptions
Negative values are invalid because shared DNA cannot be less than zero. The tool blocks these inputs at validation.
Percentage cannot exceed 100 because two people cannot share more than 100% of their autosomal DNA. Values above 100% are blocked.
cM cannot exceed the selected baseline because shared DNA cannot exceed the total autosomal cM reference value. The tool validates against your chosen baseline.
Shared DNA under 15 cM equivalent triggers a caution. Low values fall below reliable matching thresholds for most testing companies. A valid conversion does not mean the interpretation is strong. Small cM values may represent false positives, distant connections beyond genealogical relevance, or identical-by-state segments rather than identical-by-descent inheritance.
Closing
The core value of this tool is fast two-way conversion between shared DNA percentage and shared cM using a chosen baseline. Relationship output is only approximate context to support interpretation after conversion.
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