| P1 | P2 | Child |
|---|---|---|
| A | A | A, O |
| A | B | A, B, AB, O |
| A | AB | A, B, AB |
| A | O | A, O |
| B | B | B, O |
| B | AB | A, B, AB |
| B | O | B, O |
| AB | AB | A, B, AB |
| AB | O | A, B |
| O | O | O |
What You Get with Our Free Blood Type Calculator
Instant Blood Type Prediction
Enter the mother’s and father’s blood types and get every possible child blood type calculated instantly with the probability percentage for each outcome.
ABO and Rh Factor Combined
Our calculator covers both the ABO blood group system and the Rh positive or negative factor together for a complete blood type prediction including A+, B+, AB+, O+, and all negative variants.
See which blood types are compatible for transfusion purposes. Know which types can donate to and receive from each other based on standard compatibility rules.
Rarest and Most Common Blood Types
Learn where your blood type falls in the rarity spectrum. See the population frequency of every blood type from the most common O positive to the rarest AB negative.
Universal Donor and Receiver Info
Understand why O negative is the universal donor and AB positive is the universal receiver with clear explanations of the genetics behind blood type compatibility.
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No account needed, no download required, no limits at all. Calculate blood type predictions as many times as you want completely free right now.
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Why Our Blood Type Calculator Gets It Right
Blood type inheritance follows Mendelian genetics where each parent contributes one ABO allele and one Rh allele to the child. The ABO system has three alleles — A, B, and O — where A and B are codominant and O is recessive. The Rh factor has two alleles where positive is dominant over negative. Calculating every possible child blood type requires working through every allele combination both parents could contribute which produces a probability distribution rather than a single answer.
Our blood type calculator generates a complete probability table for every possible child blood type based on the parents’ phenotypes. When both parents are O positive the calculator accounts for the possibility that one or both parents carry a hidden recessive Rh negative allele which means their child could potentially be O negative even though both parents are positive. Many basic calculators miss this nuance.
The blood type compatibility chart adds practical medical value beyond genetic curiosity. Understanding which blood types can safely receive transfusions from which donors is genuinely important information especially in emergency contexts. Our calculator includes this compatibility data alongside the genetic predictions so you get both the hereditary science and the practical medical application in one tool.
Explore more free health calculator tools: BMI Calculator, Interest Calculator, and our full Calculator Tools collection. Learn about blood type genetics at Wikipedia.
How Blood Type Calculator Works
Calculate possible child blood types in four simple steps.
Enter Your Details
Select the mother’s blood type and the father’s blood type from the dropdown menus. Both ABO group and Rh factor are included.
Click Calculate
Hit calculate and get every possible child blood type instantly with the probability percentage for each outcome clearly displayed.
Get Your BMI Result
Check the probability table to see which blood types are possible, which are most likely, and which are impossible based on the parental combination.
Learn About Compatibility
View the blood type compatibility chart to understand transfusion compatibility and where your blood type falls in the rarity and frequency spectrum.
Frequently Asked Questions About Blood Type Calculator
Here are answers to the most common questions about blood type calculators, how blood type inheritance works, and which blood types are the rarest and most common worldwide.
What is a blood type calculator?
BMI (Body Mass Index) is a simple measurement that compares your weight and height to determine if you are underweight, normal, overweight, or obese.
What is the rarest blood type?
BMI is calculated using the formula: weight (kg) ÷ height (m²). Our calculator does this instantly for you with accurate results.
What is the most common blood type?
BMI is a general health indicator and may not account for muscle mass, age, or body composition, but it is widely used as a quick health screening tool.