Blood Type Calculator

Predict possible blood types for offspring based on parents' ABO and Rh blood types. See inheritance probabilities with interactive Punnett squares.

Parent 1 Blood Type
Parent 2 Blood Type

Combined Punnett Square

Possible Blood Types for Offspring

How Blood Type Works

Blood type is determined by two genetic systems:

  • ABO System: Controlled by three alleles (A, B, O). A and B are codominant, both dominant over O.
  • Rh Factor: Positive (+) is dominant over negative (-).

Your blood type is written as ABO type followed by Rh (e.g., A+, O-, AB+).

ABO Blood Types

  • Type A: Genotype AA or AO
  • Type B: Genotype BB or BO
  • Type AB: Genotype AB (codominant)
  • Type O: Genotype OO (recessive)

There are 4 blood types and 6 possible genotypes in the ABO system.

Rh Factor

  • Rh Positive (+): Genotype ++ or +-
  • Rh Negative (-): Genotype --

About 85% of people are Rh positive. Rh negative is recessive and requires two negative alleles.

Inheritance Examples

Example 1: Parent 1 (A+) × Parent 2 (B+)

If both are AO and +-, possible children:

  • AB+, AB-, A+, A-, B+, B-, O+, O-
  • This couple could have children with any blood type!

Blood Type Distribution

Global average distribution:

  • O+ : 38%
  • A+ : 34%
  • B+ : 9%
  • O- : 7%
  • A- : 6%
  • AB+ : 3%
  • B- : 2%
  • AB- : 1%

Important Notes

Medical Disclaimer: This calculator is for educational purposes only. For medical advice, paternity testing, or health decisions, consult healthcare professionals. Blood type can only be definitively determined through laboratory testing.

How the odds are calculated: When a parent's exact genotype is unknown (e.g. type A could be AA or AO), the calculator assumes the parent carries the recessive allele (AO). This shows every blood type the couple could have and keeps the Punnett square and probability table consistent.