Explore the Punnett Square Calculator
Cross two parents and get genotype and phenotype ratios, for one trait or two. Free, no signup, runs in your browser.
- Free to use
- No signup
- Nothing to install
- Runs in your browser
Illustration. Open the tool for the real thing.
See it in action
The Punnett Square Calculator with sample data entered and the result showing.
What is the Punnett Square Calculator?
Cross two parents and get genotype and phenotype ratios, for one trait or two. It runs in your browser, so a change to a setting or a drag on an object shows up at once.
Genetic counsellors, plant breeders and animal breeders use Punnett squares to predict traits in offspring and to plan crosses.
3 steps to your result
Open the tool and follow along. Nothing to install.
What you get
Each parent passes one allele of each gene to the offspring, chosen at random.
A monohybrid cross Aa × Aa gives a 3:1 phenotype ratio.
A dihybrid cross AaBb × AaBb gives the classic 9:3:3:1 ratio.
Cross Rr × Rr and read the 3:1 ratio.
Cross a homozygous dominant with a homozygous recessive.
Try a dihybrid cross to see 9:3:3:1.
Used for
Pick one to see how it fits.
Biology learners
Biology students and teachers who want to explore living systems, populations and genetics interactively and safely.
Try it freeTeachers
For teachers: project the Punnett Square Calculator on the board, let students predict the result, then run it together and test this: Cross a homozygous dominant with a homozygous recessive. For students: change one thing at a time and write down what changes.
Try it freeHow it compares
A plain look at this tool next to the usual alternative.
| This simulation | Textbook diagram | |
|---|---|---|
| Interactive | Drag, tap and change settings | Fixed picture |
| Install | Nothing to install | Not needed |
| Cost | Free to use | Depends on the book |
Questions people ask
What is the difference between genotype and phenotype?
Genotype is the pair of alleles an organism carries, such as Rr. Phenotype is the visible trait, such as round seeds.
What is a dihybrid cross?
A cross that follows two genes at once. Each parent makes four kinds of gametes, so the Punnett square is 4 by 4.
Is the Punnett Square Calculator free to use?
Yes. The Punnett Square Calculator is free, needs no signup or download and runs in your web browser. It is part of the Biology group of AZRS simulations.
Does the Punnett Square Calculator work on a phone or tablet?
Yes. The Punnett Square Calculator takes touch input as well as mouse input, so you can use its 5 adjustable settings with a finger. A larger screen makes the controls and graphs easier to read.
How do I use the Punnett Square Calculator?
1. In the Punnett Square Calculator, use the controls to change Type of cross, Parent 1: seed shape (R = round, r = wrinkled), Parent 2: seed shape, Parent 1: seed colour (Y = yellow, y = green), Parent 2: seed colour. The simulation reacts instantly. 2. In the Punnett Square Calculator, pick an option such as Monohybrid, Dihybrid to switch modes or load an example. 3. In the Punnett Square Calculator, press "Simulate 100 offspring" to start, reset or change what is happening. 4. Start with this experiment: Cross Rr × Rr and read the 3:1 ratio. Drag any glowing handle, object or slider with your mouse or finger and the Punnett Square Calculator responds in real time. 5. Change one setting at a time and watch which readout moves, then compare it with this idea: Each parent passes one allele of each gene to the offspring, chosen at random.
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Try the Punnett Square Calculator now
Cross two parents and get genotype and phenotype ratios, for one trait or two. Free to use.
Try it free