Blood Type Calculator - Punnett Inheritance Predictor

A blood type calculator predicts a child's ABO and Rh blood type from the parents' phenotypes. It builds two independent Punnett squares, one for the ABO gene and one for the Rh gene, and gives the chance of each common blood type.

• • Expectant parents: Want a quick estimate of which blood types their baby could be born with.
• • Family curiosity: Want to know why a child has a different blood type than either parent, such as two A parents having an O child.
• • Blood donation planning: Want a quick sense of which family members could share a rare type, for example AB negative.
• • Biology and genetics homework: Need a worked Punnett-style example for a 3-allele trait combined with a single dominant/recessive Rh gene.

Blood type is set by two independent genes. The ABO gene gives A, B, AB, and O, and the Rh gene gives the positive or negative part. The calculator multiplies the ABO probability by the Rh probability to get a full type such as A positive, and the eight-row table always sums to 100%.

If you are tracking the pregnancy itself, Pregnancy Due Date Calculator turns the first day of your last period into a delivery window.

The calculator maps each parent's phenotype to an allele pair, builds a Punnett square for each gene, sums the phenotype probabilities, and multiplies the ABO and Rh probabilities to get a full blood type. The heterozygous-only assumption applies when a phenotype could come from more than one genotype.

• ABO gene: Three common alleles: A, B, and O. A and B are co-dominant and both are dominant over O. Phenotype mapping: A -> AO, B -> BO, AB -> AB, O -> OO under the heterozygous assumption.
• Rh gene: Two common alleles: D (Rh positive, dominant) and d (Rh negative, recessive). Phenotype mapping: Rh+ -> Dd, Rh- -> dd under the heterozygous assumption.
• Heterozygous assumption: When a parent has type A blood, the calculator assumes AO rather than AA. The same applies to type B and to Rh+ parents. This keeps recessive outcomes possible in the prediction.

The ABO and Rh Punnett squares are independent, so the calculator multiplies their probabilities to get the eight full blood types. A 50% chance of ABO A combined with a 75% chance of Rh+ gives a 37.5% chance of A positive, and the full list always sums to 100%.

According to MedlinePlus Medical Encyclopedia (U.S. National Library of Medicine), The four major blood types are A, B, AB, and O, and the Rh factor is a separate cell-surface protein that makes a blood type positive or negative.

According to Omni Calculator (Blood Type), When both parents are Rh-positive the child has a 75% chance of being Rh-positive and a 25% chance of being Rh-negative, and when both parents have type A blood the child has a 75% chance of type A and a 25% chance of type O under the heterozygous assumption.

The Blood Pressure Calculator is a useful companion for routine prenatal and postnatal cardiovascular monitoring alongside the blood type result.

Four genetics terms make the calculator results much easier to read. The cards below cover the ideas you will see most often when discussing blood type inheritance.

Because the O allele is recessive, a child with type O blood must have received an O allele from each parent. That is why two type A parents can sometimes have a type O child but a type O parent cannot have a type AB child. The ABO system is one of the simplest single-gene traits used in classroom genetics.

The Rh status matters for pregnancy care in a way that ABO does not. Rh status determines who can receive whose blood, and Rh incompatibility is one reason prenatal care tracks the mother's Rh type.

The BMI Calculator is a useful companion if you are tracking overall pregnancy health markers alongside the blood type result.

The blood type calculator gives an answer in four quick steps. Each parent only needs their own ABO and Rh status, which most adults can pull from a recent blood test, a donor card, or a previous lab report.

1. 1 Choose the mother's ABO type: Select A, B, AB, or O from the first dropdown. Use the mother's own blood test result, not a guess about her genotype.
2. 2 Choose the mother's Rh factor: Select Rh+ or Rh- for the mother. If she is unsure, Rh+ is the safe default because it is more common in the U.S. population.
3. 3 Choose the father's ABO type: Select A, B, AB, or O for the father. The model is symmetric, so the order of the two parents does not change the result.
4. 4 Choose the father's Rh factor: Select Rh+ or Rh- for the father. The result updates immediately and shows the most likely child blood type and the full eight-row probability table.

If the mother is A positive and the father is O positive, the calculator returns A positive as the most likely child blood type, with 50% ABO A, 50% ABO O, and 75% Rh+ / 25% Rh- splits. A positive and O positive tie at 37.5% each.

If a predicted blood type looks surprising, the Blood Donation Due Date Calculator helps you plan the next whole-blood or Power Red donation around the standard waiting interval.

A blood type prediction is a planning aid, not a diagnosis. It answers family questions and supports decisions about pregnancy care, blood donation, and family history.

• • Quick estimate from two dropdowns: Replaces manual Punnett squares with a single result that combines ABO and Rh in one eight-row table.
• • Explains why siblings differ: Shows why two type A parents can have a type O child and why two Rh+ parents can have an Rh- child.
• • Pregnancy planning support: Highlights the Rh- case where prenatal follow-up matters, especially when the mother is Rh- and the father is Rh+.
• • Blood donation context: Provides a starting point for thinking about which relatives might share a rare type such as AB negative.
• • Honest about its limits: States up front that the model is a probability sketch based on the heterozygous assumption, so a real blood test is still the source of truth.
• • Educational use: Doubles as a worked example of co-dominance, recessive inheritance, and independent gene inheritance.

If you are actively planning a pregnancy, Pregnancy Calculator helps estimate gestational age so the conversation about blood type happens at the right time. Use the blood type prediction as a starting point for those conversations, not as a substitute for prenatal care.

A few real-world factors can shift a prediction away from the simple Punnett model. Knowing them helps you read the result as a probability rather than a promise.

• • The heterozygous-only assumption can over-predict rare outcomes, such as an O child from two type A parents who are both actually AA.
• • The calculator does not include rare ABO subgroups, weak D variants, Kell, Duffy, or other clinically important antigens. Transfusion decisions rely on a full cross-match.
• • The result is a probability sketch, not a diagnosis. For medical decisions, a laboratory blood test is the source of truth, and prenatal care should follow an obstetric clinician's guidance.

If the mother is Rh negative and the father is Rh positive, the calculator's result becomes more than a curiosity. Rh incompatibility can matter during pregnancy when an Rh- mother carries an Rh+ baby. Standard prenatal care typically gives an Rh immunoglobulin (RhoGAM) injection around week 28 and again after delivery if the baby turns out to be Rh positive, but only an obstetric clinician can decide whether the injection is needed in a specific pregnancy.

Population frequencies are a useful sanity check. A predicted AB negative child is genuinely rare even when both parents are Rh negative, so use the result to plan a conversation, not to expect a specific outcome.

According to American Red Cross - Blood Types, The approximate U.S. distribution of blood types is 38% O positive, 7% O negative, 34% A positive, 6% A negative, 9% B positive, 2% B negative, 3% AB positive, and 1% AB negative.

For another single-gene trait that follows similar Mendelian logic, Baby Eye Color Calculator works with three eye-color alleles the same way this calculator works with the three ABO alleles.