Blood Type Calculator
Use this blood type calculator to see the possible ABO and Rh blood types a child could inherit from two parents.
Updated September 18, 2026
Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How Blood Type Inheritance Is Calculated
Blood type is determined by two separate genetic systems inherited independently of each other, ABO type and Rh factor. Both follow standard, well-established Mendelian inheritance patterns, which makes it possible to work out every blood type a child could possibly inherit from two known parents, even without knowing either parent's exact underlying genotype¹.
What This Calculator Measures
This shows every ABO and Rh combination a child could inherit from two parents, with the probability of each, based on standard genetics. It's an educational tool for understanding inheritance patterns, not a way to determine or confirm parentage.
The Formula
The ABO gene has three alleles: A and B are codominant, O is recessive. A person's genotype (e.g. AO, BO, AA, AB, OO) isn't directly knowable from phenotype alone for type A or B, someone with type A blood could be genotype AA or AO, and someone with type B could be BB or BO¹. This calculator presents all genotype possibilities consistent with each stated phenotype, then crosses them using a standard Punnett square.
Rh factor works separately: the D antigen present (+) is dominant over absent (−), and Rh is inherited independently of ABO type². It's calculated on its own, then combined with the ABO result to give the full range of possible blood types.
How This Calculator Computes Your Result
Enter each parent's ABO type and Rh factor. We expand each parent's stated type into every genotype consistent with it, cross all combinations, and return every possible offspring blood type along with its probability.
A Note on Accuracy
This shows possible outcomes based on standard inheritance patterns, not a guarantee, and cannot determine parentage. It should never be used or interpreted as a paternity test. Rare exceptions to standard ABO inheritance exist (e.g. the Bombay phenotype), this calculator covers the standard case, not every documented genetic exception.
Frequently Asked Questions
Can this calculator determine paternity?
No. This is a genetics education tool showing possible inherited blood types based on standard Mendelian inheritance. It cannot determine parentage and should never be used or interpreted as a paternity test.
Why does it show probabilities instead of one answer?
A parent's exact genotype often can't be determined from their blood type alone, type A could be genotype AA or AO, type B could be BB or BO¹, so the calculator shows the full range of possible offspring outcomes with their probabilities.
What does it mean if a blood type isn't listed as possible?
Some combinations are biologically impossible given the parents' types, for example, two type O parents cannot have a type A or B child, since type O carries no A or B allele to pass on.
Does this cover every genetic exception?
No. Rare exceptions to standard ABO inheritance exist, such as the Bombay phenotype. This calculator covers the standard case taught in genetics education, not every documented exception.
Sources
ABO Gene: ABO, Alpha 1-3-N-Acetylgalactosaminyltransferase and Alpha 1-3-Galactosyltransferase, NIH MedlinePlus Genetics
RHD Gene: Rh Blood Group, D Antigen, NIH MedlinePlus Genetics
Blood Type Calculator
Use this blood type calculator to see the possible ABO and Rh blood types a child could inherit from two parents.
Updated September 18, 2026
Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How Blood Type Inheritance Is Calculated
Blood type is determined by two separate genetic systems inherited independently of each other, ABO type and Rh factor. Both follow standard, well-established Mendelian inheritance patterns, which makes it possible to work out every blood type a child could possibly inherit from two known parents, even without knowing either parent's exact underlying genotype¹.
What This Calculator Measures
This shows every ABO and Rh combination a child could inherit from two parents, with the probability of each, based on standard genetics. It's an educational tool for understanding inheritance patterns, not a way to determine or confirm parentage.
The Formula
The ABO gene has three alleles: A and B are codominant, O is recessive. A person's genotype (e.g. AO, BO, AA, AB, OO) isn't directly knowable from phenotype alone for type A or B, someone with type A blood could be genotype AA or AO, and someone with type B could be BB or BO¹. This calculator presents all genotype possibilities consistent with each stated phenotype, then crosses them using a standard Punnett square.
Rh factor works separately: the D antigen present (+) is dominant over absent (−), and Rh is inherited independently of ABO type². It's calculated on its own, then combined with the ABO result to give the full range of possible blood types.
How This Calculator Computes Your Result
Enter each parent's ABO type and Rh factor. We expand each parent's stated type into every genotype consistent with it, cross all combinations, and return every possible offspring blood type along with its probability.
A Note on Accuracy
This shows possible outcomes based on standard inheritance patterns, not a guarantee, and cannot determine parentage. It should never be used or interpreted as a paternity test. Rare exceptions to standard ABO inheritance exist (e.g. the Bombay phenotype), this calculator covers the standard case, not every documented genetic exception.
Frequently Asked Questions
Can this calculator determine paternity?
No. This is a genetics education tool showing possible inherited blood types based on standard Mendelian inheritance. It cannot determine parentage and should never be used or interpreted as a paternity test.
Why does it show probabilities instead of one answer?
A parent's exact genotype often can't be determined from their blood type alone, type A could be genotype AA or AO, type B could be BB or BO¹, so the calculator shows the full range of possible offspring outcomes with their probabilities.
What does it mean if a blood type isn't listed as possible?
Some combinations are biologically impossible given the parents' types, for example, two type O parents cannot have a type A or B child, since type O carries no A or B allele to pass on.
Does this cover every genetic exception?
No. Rare exceptions to standard ABO inheritance exist, such as the Bombay phenotype. This calculator covers the standard case taught in genetics education, not every documented exception.
Sources
ABO Gene: ABO, Alpha 1-3-N-Acetylgalactosaminyltransferase and Alpha 1-3-Galactosyltransferase, NIH MedlinePlus Genetics
RHD Gene: Rh Blood Group, D Antigen, NIH MedlinePlus Genetics
Blood Type Calculator
Use this blood type calculator to see the possible ABO and Rh blood types a child could inherit from two parents.
Updated September 18, 2026
Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How Blood Type Inheritance Is Calculated
Blood type is determined by two separate genetic systems inherited independently of each other, ABO type and Rh factor. Both follow standard, well-established Mendelian inheritance patterns, which makes it possible to work out every blood type a child could possibly inherit from two known parents, even without knowing either parent's exact underlying genotype¹.
What This Calculator Measures
This shows every ABO and Rh combination a child could inherit from two parents, with the probability of each, based on standard genetics. It's an educational tool for understanding inheritance patterns, not a way to determine or confirm parentage.
The Formula
The ABO gene has three alleles: A and B are codominant, O is recessive. A person's genotype (e.g. AO, BO, AA, AB, OO) isn't directly knowable from phenotype alone for type A or B, someone with type A blood could be genotype AA or AO, and someone with type B could be BB or BO¹. This calculator presents all genotype possibilities consistent with each stated phenotype, then crosses them using a standard Punnett square.
Rh factor works separately: the D antigen present (+) is dominant over absent (−), and Rh is inherited independently of ABO type². It's calculated on its own, then combined with the ABO result to give the full range of possible blood types.
How This Calculator Computes Your Result
Enter each parent's ABO type and Rh factor. We expand each parent's stated type into every genotype consistent with it, cross all combinations, and return every possible offspring blood type along with its probability.
A Note on Accuracy
This shows possible outcomes based on standard inheritance patterns, not a guarantee, and cannot determine parentage. It should never be used or interpreted as a paternity test. Rare exceptions to standard ABO inheritance exist (e.g. the Bombay phenotype), this calculator covers the standard case, not every documented genetic exception.
Frequently Asked Questions
Can this calculator determine paternity?
No. This is a genetics education tool showing possible inherited blood types based on standard Mendelian inheritance. It cannot determine parentage and should never be used or interpreted as a paternity test.
Why does it show probabilities instead of one answer?
A parent's exact genotype often can't be determined from their blood type alone, type A could be genotype AA or AO, type B could be BB or BO¹, so the calculator shows the full range of possible offspring outcomes with their probabilities.
What does it mean if a blood type isn't listed as possible?
Some combinations are biologically impossible given the parents' types, for example, two type O parents cannot have a type A or B child, since type O carries no A or B allele to pass on.
Does this cover every genetic exception?
No. Rare exceptions to standard ABO inheritance exist, such as the Bombay phenotype. This calculator covers the standard case taught in genetics education, not every documented exception.
Sources
ABO Gene: ABO, Alpha 1-3-N-Acetylgalactosaminyltransferase and Alpha 1-3-Galactosyltransferase, NIH MedlinePlus Genetics
RHD Gene: Rh Blood Group, D Antigen, NIH MedlinePlus Genetics