Punnett Square Calculator
Work out the genotype and phenotype ratios from a single-gene cross.
The classic 3:1 ratio
Two heterozygous parents (Aa × Aa) produce 25% AA, 50% Aa and 25% aa — a 1:2:1 genotype ratio that shows up as 3:1 in appearance, because AA and Aa look identical when A is fully dominant. Mendel's pea experiments produced 2.96:1 across nearly 20,000 plants, which is what convinced him something discrete was being inherited.
What this page needs from you
This page asks for parent 1 genotype and parent 2 genotype. From those it returns chance of the dominant phenotype in %, together with aa offspring, aa offspring, aa offspring and recessive phenotype. Every figure updates as you type, and nothing you enter leaves your browser.
Reproducibility depends on the inputs
The arithmetic here is exact; the measurements feeding it usually are not. Pipetting error, incomplete mixing and drift in a spectrophotometer all propagate straight through. Where a result matters, run it in duplicate and compare rather than trusting a single reading.
The formula
Cross each allele of one parent with each allele of the other; four equally likely combinations
Every result on this page comes from this formula. Nothing is rounded until the final display, so figures match a spreadsheet to the cent.
How to use the Punnett Square Calculator
- Fill in each field with your own figures — the defaults are only there as an example.
- The result updates as you type, so there is no button to press.
- Check the breakdown under the main result for the supporting numbers.
- Use the copy button to take the result with you, or share the link to reload the same inputs.
Punnett Square Calculator — frequently asked questions
Is this punnett square calculator free to use?
Yes. Every calculator on the site is free, needs no sign-up, and runs entirely in your browser, so your figures never leave your device.
How accurate is the result?
The maths is exact for the formula shown on the page. Accuracy in the real world depends on your inputs and on assumptions the formula cannot see, so treat the output as a well-grounded estimate rather than a quote.
Can I use it on my phone?
Yes. The page is responsive, weighs a few kilobytes and works offline once loaded, so it behaves the same on a phone as on a desktop.
What people search for
This page answers each of these searches. They are the exact phrases visitors use to find the punnett square calculator.
- punnett square calculator
- mendelian cross
- inheritance calculator
- aa x aa cross
- genotype probability
- monohybrid cross
About this calculator
Written and reviewed by The Samsung Calculator editorial team. Every calculator is written against a published formula, reviewed against at least one independent reference implementation, and dated when it changes.
Last reviewed September 14, 2026 · Calculation runs client-side · No data collected · Report an error