Can this establish paternity?

No. Simplified blood-type inheritance cannot establish paternity. Use qualified laboratory testing for that question.

Punnett Square Calculator

Tool workspace

Your input stays in this browser.

Ready

Run the tool when your input is ready.

Input

Cross type

Parent 1

Use AaBb, AO Dd, or XAXa for the selected cross type.

Parent 2

Use matching genes, an ABO genotype, or XAY for the selected cross type.

Dominance

Ready for a result

Calculate exact genotype and phenotype ratios for up to four genes, ABO/Rh blood types, and recessive X-linked classroom crosses.

Worked example result

Select Load example to use these values in the calculator.

Cross type: autosomal
Parent 1: AaBb
Parent 2: AaBb
Dominance: complete

Phenotype ratio

9:3:3:1Dominant A, Dominant B : Dominant A, recessive b : recessive a, Dominant B : recessive a, recessive b

Gametes per parent

Parent 1 gametes: AB, Ab, aB, ab
Parent 2 gametes: AB, Ab, aB, ab
Equally likely cells: 16

Punnett square

Parent 1 / Parent 2	AB	Ab	aB	ab
AB	AABB	AABb	AaBB	AaBb
Ab	AABb	AAbb	AaBb	Aabb
aB	AaBB	AaBb	aaBB	aaBb
ab	AaBb	Aabb	aaBb	aabb

Genotypes

Genotype	Count	Fraction	Percent
AABB	1	1/16	6.25%
AABb	2	1/8	12.5%
AaBB	2	1/8	12.5%
AaBb	4	1/4	25%
AAbb	1	1/16	6.25%
Aabb	2	1/8	12.5%
aaBB	1	1/16	6.25%
aaBb	2	1/8	12.5%
aabb	1	1/16	6.25%

Phenotypes (ratio order)

Phenotype	Count	Fraction	Percent
Dominant A, Dominant B	9	9/16	56.25%
Dominant A, recessive b	3	3/16	18.75%
recessive a, Dominant B	3	3/16	18.75%
recessive a, recessive b	1	1/16	6.25%

Assumptions: independent assortment, no linkage, Mendelian single-gene traits, and equal gamete viability. The selected dominance rule applies to every gene.

Embed this tool

Copy this iframe into your page.

<iframe src="https://toolfactory.diffwise.app/embed/punnett-square-calculator" title="Punnett Square Calculator" width="100%" height="760" loading="lazy" allow="clipboard-write" style="border:0"></iframe>

Select the code and copy it. You can change the height to fit your page.

The model combines each parent’s distinct gametes and counts the resulting genotypes and phenotypes.

The result includes a Punnett square, probability fractions, and ratios in the displayed table order.

Check an inheritance exercise with two independently assorting traits.

Select an inheritance model and parental genotypes

Choose Cross type.
Enter both parent genotypes.
For autosomal crosses, choose Dominance, then select Calculate Punnett square.

Cross AaBb with AaBb

Input: AaBb × AaBb

Settings: Cross type: Autosomal; Dominance: Complete

Result: 9:3:3:1

The 16 cells give Dominant A, Dominant B nine cells and recessive a, recessive b one cell.

Inheritance assumptions and probability limits

The model assumes independent assortment and equal gamete viability.
It does not model linkage, penetrance, or gene interactions.
X-linked crosses omit X-inactivation effects.