Punnett Square Calculator

Work out punnett square instantly with clear inputs, formula shown and shareable results.

About Punnett Square Calculator

Builds the two-by-two Punnett square for a monohybrid cross and reports genotype and phenotype expectations.

Formula

Monohybrid cross

Each parent contributes one allele per gamete; Aa x Aa gives 1 AA : 2 Aa : 1 aa, a 3:1 phenotype ratio

Worked example

With the default values below, Punnett Square Calculator returns Dominant phenotype expected of 75.00%. Change any input above and every figure here is recalculated in your browser.

Inputs used

First parent genotypeone of AA, Aa, aa: Aa
Second parent genotypeone of AA, Aa, aa: Aa
Offspring expectedaccepts 1–100,000: 100

Results

Dominant phenotype expected: 75.00%
Recessive phenotype expected: 25.00%
Genotype ratio: 1 AA : 2 Aa : 1 aa
Expected recessive offspring: 25.00

Step by step

1Values used
2Monohybrid cross
3Dominant phenotype expected= 75.00
4Recessive phenotype expected= 25.00
5Genotype ratio= 1 AA : 2 Aa : 1 aa
6Expected recessive offspring= 25.00

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Are the ratios exact?

They are expectations. Small families deviate widely because fertilisation is a random sampling process.

What about incomplete dominance?

Then the heterozygote has its own intermediate phenotype and the ratio becomes 1:2:1 by phenotype as well.