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BloodTypeCalc.com

Interactive inheritance tool

Blood Type Punnett Square Calculator

Choose the parents' blood types to explore the ABO and Rh alleles a child could inherit. When a parent's exact genotype is unknown, the calculator shows every compatible genetic scenario instead of guessing.

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  • Nothing is saved
  • Educational use only
By BloodTypeCalc.com Editorial TeamPublished Suggest a correction
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How to read the square

  1. 1. Find each parent’s alleles

    Use the labels beside and above the grid.

  2. 2. Follow one allele from each parent into a cell

    Each cell combines one contribution from each parent.

  3. 3. Count the resulting child genotypes and phenotypes

    The four cells produce the exact percentages for that scenario.

Important limitations: This tool shows common ABO inheritance patterns and a simplified Rh model. Rare blood-group variants, weak antigen expression, laboratory discrepancies, transfusions, stem-cell transplants, and other biological factors can produce results that require professional interpretation. Blood-type inheritance cannot confirm paternity. Use validated genetic testing for questions about biological relationships.

Parent Blood Type CalculatorRh Factor & PregnancyBlood Type Compatibility Chart

Understanding ABO inheritance

The ABO system uses A, B, and O alleles. A and B are codominant with each other, while both are dominant over O. That produces six common genotypes: AA, AO, BB, BO, AB, and OO.

Read the complete ABO inheritance guide

Understanding the Rh model

For education, this tool models RhD as D dominant over d: DD and Dd are Rh positive, while dd is Rh negative. Clinical Rh typing includes variants and other antigens that a 2×2 square cannot capture.

Learn how Rh factor is inherited

Punnett square questions

What is a blood type Punnett square?
A Punnett square is a visual way to list the allele combinations a child could inherit from two parents. Each parent contributes one allele, producing four equally likely cells in a specific genotype scenario.
Can a type O parent have a type AB child?
Under the standard ABO model, a type O parent can pass only an O allele, so they cannot contribute the A or B allele needed for a type AB child. Rare variants and testing discrepancies require professional interpretation.
Why can type A blood have two genotypes?
A is dominant over O, so both AA and AO produce type A blood. A routine blood type result does not reveal which of those genotypes a person has.
Can two Rh-positive parents have an Rh-negative child?
Yes. In the simplified RhD model, two Rh-positive parents can each be Dd. If both pass the d allele, their child can be dd and Rh negative.
Can two Rh-negative parents have an Rh-positive child?
Under the simplified D/d model, two Rh-negative parents are both dd and can pass only d, so their child is expected to be Rh negative. Clinical Rh typing is more complex than this model.
Can a Punnett square prove paternity?
No. Blood type inheritance cannot establish paternity. Questions about biological relationships require validated DNA testing and qualified interpretation.
Why does the calculator show a probability range?
A visible blood type does not always reveal the underlying genotype. Rather than guessing or averaging hidden genotypes, the calculator reports the minimum and maximum across every compatible scenario.
Are rare blood-type variants included?
No. This tool uses the common ABO model and a simplified single-locus RhD model. It does not model rare ABO variants, weak or partial D, other Rh antigens, transfusions, transplantation, or laboratory error.

Sources

Information on this page is paraphrased from the following authoritative sources.

  1. Facts About Blood and Blood Types(opens in a new tab)American Red Cross
  2. Blood typing(opens in a new tab)MedlinePlus, U.S. National Library of Medicine
  3. The Rh Factor: How It Can Affect Your Pregnancy(opens in a new tab)American College of Obstetricians and Gynecologists (ACOG)
  4. The Rh blood group(opens in a new tab)NCBI Bookshelf, National Library of Medicine