Blood Type Calculator
Use this blood type calculator to see which blood types your baby could have, with real percentages and Punnett squares. You can also check which father blood types are possible for a child and find out who you can donate blood to.
- Exact odds for all 8 types
- ABO and Rh Punnett squares
- Paternity exclusion check
- Free, private, no sign-up
Parent 1 blood type
Parent 2 blood type
Leave genotypes on Unknown unless a genetic test or family history tells you. For example, a type A parent with a type O parent of their own must be AO.
Most likely blood type
30.8%
chance for each child
Odds for every blood type
Punnett squares for these parents
Each square shows the four equally likely gene combinations a child can inherit.
ABO blood group
Rh factor
Mother's blood type
Child's blood type
Blood types can rule a man out as the biological father, but they can never prove paternity. Only a DNA test can do that.
Possible father blood types
4 of 8
blood types are possible
Your blood type
This shows standard ABO and Rh compatibility. Hospitals always cross-match blood in the lab before a transfusion.
Your donor profile
6.6%
of people in the US share your type
A blood type calculator that gives real answers
Most blood type charts only say what is possible. This calculator shows how likely each type is, explains why, and covers paternity and donation too.
Percentages, not just possibilities
See the exact chance of all eight blood types, from A positive to O negative, for each child.
Genotype aware
Know a parent is AO or Dd? Set it and the odds update. Unknown genotypes use real population frequencies.
Punnett squares
Visual ABO and Rh squares show exactly which gene pairs a baby can inherit from each parent.
Paternity exclusion
Enter the mother and child to see which father blood types are possible and which are ruled out.
Donor compatibility
Find out who you can give red cells and plasma to, who you can receive from, and how rare your type is.
Private by design
No account and no data stored. Everything is calculated in your browser, and a link saves your result.
How to use the blood type calculator
Results update the moment you tap a blood type.
- Pick both parents' blood typesTap the ABO group and Rh factor for each parent, for example A+ and B+.
- Add genotypes if you know themLeave them on Unknown otherwise. The calculator weighs each possibility for you.
- Read the oddsSee the most likely type, the chance of every type and which ones are impossible.
- Check the Punnett squaresSee how each parent's genes combine to produce those results.
- Try paternity or donor modeSwitch tabs to check possible fathers or your donation matches.
How blood type inheritance works
Your blood type is set by two genes. The ABO gene has three versions, called alleles: A, B and O. A and B are codominant, so a person with one of each is type AB, while O is recessive and only shows when someone has two copies. Each parent passes one ABO allele to the child at random.
The Rh factor works the same way. The D allele makes you Rh positive and is dominant over d, so only people with two d alleles are Rh negative. That is why two Rh positive parents can still have an Rh negative baby if both carry d.
Worked example: AO and BO parents
A type A parent who carries O (AO) and a type B parent who carries O (BO) can have a child of any ABO type, each with a 25% chance.
| Alleles | B (from parent 2) | O (from parent 2) |
|---|---|---|
| A (from parent 1) | AB: type AB | AO: type A |
| O (from parent 1) | BO: type B | OO: type O |
Blood type inheritance chart
This parents blood type chart shows every ABO combination and the child blood types that are possible or impossible.
| Parents | Child can be | Child cannot be |
|---|---|---|
| O and O | O | A, B, AB |
| O and A | A, O | B, AB |
| O and B | B, O | A, AB |
| O and AB | A, B | O, AB |
| A and A | A, O | B, AB |
| A and B | A, B, AB, O | None |
| A and AB | A, B, AB | O |
| B and B | B, O | A, AB |
| B and AB | A, B, AB | O |
| AB and AB | A, B, AB | O |
For the Rh factor: two Rh negative parents always have an Rh negative child. Any pairing with at least one Rh positive parent can produce either Rh positive or Rh negative children, depending on whether the positive parents carry the hidden d allele.
Blood donor compatibility chart
For red cell transfusions, a recipient can only receive blood that does not carry antigens their own blood lacks. That makes O negative the universal red cell donor and AB positive the universal recipient. Plasma works the other way round, so AB plasma can be given to anyone.
| Blood type | Gives red cells to | Receives red cells from | US share |
|---|---|---|---|
| O− | Everyone | O− | 6.6% |
| O+ | O+, A+, B+, AB+ | O+, O− | 37.4% |
| A− | A−, A+, AB−, AB+ | A−, O− | 6.3% |
| A+ | A+, AB+ | A+, A−, O+, O− | 35.7% |
| B− | B−, B+, AB−, AB+ | B−, O− | 1.5% |
| B+ | B+, AB+ | B+, B−, O+, O− | 8.5% |
| AB− | AB−, AB+ | AB−, A−, B−, O− | 0.6% |
| AB+ | AB+ | Everyone | 3.4% |
Expecting a baby? Track the big dates with the due date calculator and the conception calculator.
Why it helps to know blood types
A few minutes with the calculator can answer questions that otherwise mean digging through a textbook.
Plan for pregnancy. Spot a possible Rh mismatch early so you can talk to your doctor about it.
Satisfy curiosity. Find out why a child can have a different blood type from both parents.
Understand family results. Make sense of blood test results across parents, children and siblings.
Become a donor. See who your blood can help, especially if you have a rare or universal type.
Learn genetics. Punnett squares make dominant and recessive inheritance easy to see.
Help with homework. Students can check biology answers and see every step.
Blood type calculator FAQs
Clear answers to the most common questions about blood type inheritance.
It depends on the genes both parents pass on. For example, A and B parents can have a baby with any ABO type, while two O parents can only have an O baby. Use the calculator to see the odds of each type.
Not under standard inheritance. Two type O parents can only pass on O alleles, so their children are type O. Very rare exceptions exist, such as the Bombay phenotype or cis-AB, so an unexpected result should be rechecked by a lab.
Yes. An A parent and a B parent can have an O child if both carry O, or an AB child. Two Rh positive parents can also have an Rh negative child if both carry the d allele.
No. Blood type can only rule a man out. For example, a type AB man cannot father a type O child. Because many men share each blood type, only a DNA test can confirm paternity.
Rh positive (D) is dominant over Rh negative (d). A child is Rh negative only if both parents pass on d, so two Rh positive parents who both carry d have a 25% chance of an Rh negative child.
AB negative is the rarest of the eight main blood types, found in about 0.6% of people in the US. B negative is next at about 1.5%, while O positive is the most common at about 37%.
O negative red cells can be given to anyone, which makes O negative the universal red cell donor. AB positive people can receive red cells from every type. For plasma it is reversed, and AB plasma suits everyone.
If an Rh negative mother carries an Rh positive baby, her body can make antibodies that may affect a later pregnancy. An anti-D injection, often called RhoGAM, usually prevents this, so tell your doctor or midwife your blood type early.
They follow Mendelian inheritance exactly when genotypes are known. When a genotype is unknown, the calculator weighs the options using approximate global allele frequencies, so real odds can differ slightly by ancestry.
Find out your baby's possible blood types now
Tap two blood types and get the odds for every outcome in seconds, with Punnett squares, a paternity check and a donor match in the same place.
For education only. Results assume standard ABO and Rh inheritance; rare variants such as the Bombay phenotype or cis-AB can produce exceptions. Blood types cannot confirm paternity, and transfusions always require lab cross-matching. Unknown genotypes are weighted with approximate global allele frequencies (A 22%, B 16%, O 62%, Rh d 25%), so real odds vary by ancestry.