Blood Type Inheritance Calculator — What Blood Type Will My Child Have?
Calculate possible child blood types based on parents' ABO and Rh factor. Understand blood type genetics, Punnett squares, and inheritance probabilities.
Blood type questions come up more often than you'd think — during pregnancy planning, before donating blood, in some cultures where blood type influences relationships (Japanese blood type personality theory is a whole thing), and occasionally in paternity contexts. The Blood Type Calculator on CalcHub lets you explore the genetics of blood type inheritance without needing a biology degree.
The ABO System: How Blood Types Work
Your blood type is determined by antigens on the surface of your red blood cells. The ABO system has three alleles: A, B, and O.
- A and B are codominant — both express if present together (giving AB)
- O is recessive — only shows up if you have two O alleles
| Blood Type | Possible Genotypes | Antigens Present | Can Donate To | Can Receive From |
|---|---|---|---|---|
| A | AA or AO | A antigens | A, AB | A, O |
| B | BB or BO | B antigens | B, AB | B, O |
| AB | AB | A and B antigens | AB only | All types |
| O | OO | None | All types | O only |
Rh Factor: The + or − After Your Blood Type
The Rh factor is a separate antigen (the D antigen). If you have it, you're Rh+ (positive); if not, Rh− (negative). Rh+ is dominant.
| Parent 1 | Parent 2 | Possible Child Rh |
|---|---|---|
| Rh+ (Dd) | Rh+ (Dd) | 75% +, 25% − |
| Rh+ (DD) | Rh+ (DD) | 100% + |
| Rh+ | Rh− | 50% + or 100% + depending on parent genotype |
| Rh− | Rh− | 100% − |
ABO Inheritance: Punnett Square Examples
Parent 1: Type A (AO) × Parent 2: Type B (BO)| B | O | |
|---|---|---|
| A | AB | AO (Type A) |
| O | BO (Type B) | OO (Type O) |
| O | O | |
|---|---|---|
| O | OO | OO |
| O | OO | OO |
Common Blood Type Combinations and Child Possibilities
| Parent 1 | Parent 2 | Possible Child Types |
|---|---|---|
| O | O | O only |
| O | A | O, A |
| O | B | O, B |
| O | AB | A, B |
| A | A | O, A |
| A | B | O, A, B, AB |
| A | AB | A, B, AB |
| B | B | O, B |
| B | AB | A, B, AB |
| AB | AB | A, B, AB (not O) |
Blood Type Personality Theory
In Japan and South Korea, blood type personality theory (similar to Western astrology) is widely discussed:
- Type A — Organized, responsible, anxious
- Type B — Individualistic, creative, selfish (has a stigma in Japan)
- Type AB — Rational, adaptable, indecisive
- Type O — Confident, insensitive, self-determined
There's no scientific support for blood type personality correlations — but the cultural phenomenon is real enough that some job listings in Japan used to (controversially) ask for blood type.
Can a child have a blood type neither parent has?
Yes — a child of two Type A parents can be Type O if both parents carry the recessive O allele (genotype AO). This surprises people because neither parent appears to have Type O blood. The calculator shows all possible child blood types based on your inputs.
Is blood type determined at conception?
Yes. Blood type is inherited from both parents via standard Mendelian genetics. It doesn't change throughout life (barring extremely rare bone marrow transplant scenarios).
What if the child's blood type is "impossible" based on the parents?
Blood type is sometimes used in paternity testing, though DNA testing is far more conclusive. A Type AB child from two Type O parents is genetically impossible, which could indicate lab error, an extremely rare mutation, or paternity concerns.
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