Blood Type Calculator

ABO & Rh Factor Mendelian Genetics

Human blood types are inherited according to Mendelian Co-Dominant Genetics:

• ABO Gene Alleles: I^A (A antigen), I^B (B antigen), and i (O, absence of antigens):

• A and B are co-dominant to each other, while O (i) is recessive.

• Type A: Genotype AA or AO

• Type B: Genotype BB or BO

• Type AB: Genotype AB (both antigens expressed)

• Type O: Genotype OO (neither antigen expressed)

• Rh Factor (Rhesus D Antigen):

• Rh+ is dominant (DD or Dd), Rh- is recessive (dd).

• Maternal-Fetal Rh Incompatibility:

• If Mother is Rh- and Father is Rh+, fetal red blood cells can enter maternal circulation, triggering maternal anti-D antibodies against subsequent pregnancies unless prevented by RhoGAM.

How to Use This Calculator

Enter your Mother's Blood Type — select from A positive (A+), A negative (A-), B positive (B+), Father's Blood Type — select from A positive (A+), A negative (A-), B positive (B+), and Genetics Case Benchmark — select from Custom Parent Types, Mother A+ & Father B+ (All 4 Blood Types Possible), Both Parents O+ (100% O Type Offspring). Results update instantly — no submit button needed. Use metric or imperial units as labeled. For the most accurate result, measure height and weight in the morning without shoes.

The Formula

Formula Reference: Blood Type Calculator

Input variables:

motherBloodType — Mother's Blood Type

fatherBloodType — Father's Blood Type

Computed outputs:

possibleBloodTypes — Possible Child Blood Types

impossibleBloodTypes — Impossible Child Blood Types

rhIncompatibilityRisk — Rh Incompatibility Risk

mostLikelyType — Most Likely Offspring Type

Mathematical relationships extracted from calculation logic:

prob = (aboProb * rhProb) / 100.0

Standard: WHO and CDC published clinical reference standards

Worked Example

If both parents are O+, their child has a 100% chance of being O blood type; blood types A, B, and AB are genetically impossible.

Understanding Your Result

Health calculations based on standard clinical formulas give a population-reference estimate — individual variation exists. Compare your result to the reference ranges provided using validated sources (WHO, CDC, NIH, or specialty clinical guidelines). A single measurement is a starting point; meaningful health trends emerge from tracking the same metric over time under consistent conditions. For values outside reference ranges, consult a qualified healthcare provider before making changes to diet, exercise, or medication.