Blood Type Calculator — Compatibility & Inheritance
Select your blood type to instantly see who you can donate to and receive from, plus enter two parent types to predict which ABO and Rh blood types their children could inherit.
Your blood type
Parent 1 blood type
Parent 2 blood type
How does this calculator work?
Blood type is set by ABO (I_A, I_B, i alleles) and Rh (+ dominant) genes. O− can donate red cells to anyone; AB+ can receive from all types. Child blood types are predicted by Punnett square logic — each parent's possible allele combinations determine which types are genetically possible for their children.
Formula
How this is calculated
Blood type is determined by two independent systems: ABO (governed by three alleles — I_A, I_B, and recessive i) and the Rh factor (Rh+ is dominant). Your ABO blood group depends on which two alleles you inherited from your parents, and your phenotype (A, B, AB, or O) results from those alleles. An O person carries two recessive i alleles; A carries I_A/I_A or I_A/i; B carries I_B/I_B or I_B/i; AB carries one each of I_A and I_B.
Compatibility for transfusion is determined by antigens on red blood cells and antibodies in plasma. For example, an O− donor has no A, B, or Rh antigens and is the "universal donor" for red cells. An AB+ recipient can accept all types because they carry all antigens and form no corresponding antibodies. The calculator looks up these fixed compatibility tables rather than computing from alleles, since clinical rules also depend on antibody screening.
For inheritance, the tool applies a simplified Punnett square: each parent is assumed to be heterozygous for their ABO group (except O and AB, which are unambiguous). This means the output lists all *possible* child types — an individual child may only have one of those types. Rh+ parents may carry a recessive Rh− allele, so their children could be either Rh+ or Rh−; only two Rh− parents guarantee an Rh− child.
Frequently asked questions
O− is the universal donor for red blood cells because it carries no ABO or Rh antigens — it is safe for any recipient in an emergency. AB+ is the universal recipient because those individuals have all antigens and make no corresponding antibodies, so they can accept any blood type.
Blood type genes come in pairs, and you can carry a recessive allele silently. For example, an A+ parent may carry a hidden O allele, so with an O+ partner their child could be O+. Similarly, Rh+ parents can both carry the recessive Rh− allele and produce an Rh− child.
Blood type is genetically fixed for life in healthy individuals. Rare exceptions include bone marrow transplants, where a donor's stem cells can change the recipient's blood type, and certain cancers that affect antigen expression — but these are medical special cases, not normal variation.
TG we-Calculate Editorial Team. (2026). Blood Type Calculator — Compatibility & Inheritance [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/blood-type-calculator
TG we-Calculate Editorial Team. "Blood Type Calculator — Compatibility & Inheritance." TG we-Calculate. 2026. https://we-calculate.com/calculator/blood-type-calculator.
TG we-Calculate Editorial Team, "Blood Type Calculator — Compatibility & Inheritance," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/blood-type-calculator
@misc{wecalculate_blood_type_calculator, title = {Blood Type Calculator — Compatibility & Inheritance}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/blood-type-calculator}}, year = {2026}, note = {TG we-Calculate} }
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