Punnett square calculator
What will your child inherit?
Pick each parent's traits. Watch the odds across traits, from earlobes to blood groups.
No trait matches that search.
How the Punnett square works
What is a Punnett square?
A Punnett square is a small grid that shows every way two parents can pass on one gene. Each parent gives one of their two copies, so the mother's copies run across the top and the father's copies run down the side. Each box is one possible child, and every box is equally likely.
How do I use this calculator?
Pick a trait from the list, then tap the look that the mother and the father each have. Add the grandparents if you know them, because they can reveal hidden copies. The ring shows the child's odds, and the square below it shows how each pairing of gene copies plays out. Anyone left unset counts as a typical person.
What do letters like Bb or ll mean?
Each letter stands for one copy of a gene, and everyone has two copies. A capital letter marks the version that wins when it meets a different one. A lowercase letter marks the version that shows only in pairs. So Bb has one of each, and ll has two copies of the hidden version.
Can two brown-eyed parents have a blue-eyed child?
Yes. A brown-eyed parent can carry a hidden blue copy. If both parents carry one and each passes it on, the child gets two blue copies. In the classic model that happens one time in four when both parents are carriers. Real eye color involves more genes, so surprises happen in both directions.
What does it mean to be a carrier?
A carrier has one hidden copy of a gene and one copy that shows. The copy that shows is enough, so a carrier often never knows. When two carriers have a child, each child has a one in four chance of getting two hidden copies, as when two dark-haired parents have a red-haired child.
Why do sons and daughters get different odds for some traits?
Some genes sit on the X chromosome. A daughter gets an X from each parent, but a son gets his only X from his mother and a Y from his father. One changed copy on the X is therefore enough to affect a son, which is why red-green color blindness is far more common in boys.
How accurate are these odds?
For single-gene traits such as blood type, Rh factor and earwax, the odds follow well-tested rules. Traits marked Simplified model, such as tongue rolling or earlobes, depend on many genes, so treat them as a game. This page is for learning, not medical advice. A genetic counselor can give real figures for health conditions.
Can I add my own trait?
Yes. Tap Add a trait, give it a name and two looks, and say whether one look wins, the looks blend, or it rides on the X chromosome. To add a missing look, such as gray eyes, tap Add a look under Mother or Father. Your traits and looks stay in your browser, and nobody else sees them.
Every trait in this calculator
Tap a name to open that trait above. “Simplified model” marks a classroom version of a trait that really depends on many genes.
Looks
- Eye color (Brown, Green or Blue). Brown (B) masks green and blue, and green (G) masks blue. Simplified model
- Hair texture (Curly, Wavy or Straight). A teaching example of incomplete dominance: one curly (C) and one straight (S) copy blend into wavy hair. Simplified model
- Red hair (Not red or Red). Red hair mostly comes from two red-hair versions of the MC1R gene (m).
- Height (Short, Below average, Average, Above average or Tall). Real height comes from thousands of gene versions that each add or take away a few millimetres, plus food, sleep and health in childhood. Simplified model
- Skin tone (Very light, Light, Medium, Dark or Very dark). Skin tone comes from many genes that each change how much melanin, the brown pigment, the skin makes. Simplified model
- Eye shape (Almond or Round). Almond-shaped eyes are often taught as dominant (A) and round eyes as recessive. Simplified model
- Earlobes (Free or Attached). The classroom rule says free earlobes (E) mask attached ones. Simplified model
- Widow's peak (Widow's peak or Straight). Textbooks call a V-shaped hairline dominant (W). Simplified model
- Cheek dimples (Dimples or None). Dimples run in families and are often taught as dominant (D), but they can come and go with age. Simplified model
- Cleft chin (Cleft or Smooth). A dimple in the chin is taught as dominant (C). Simplified model
- Freckles (Freckles or None). Freckles are taught as dominant (F). Simplified model
- Tongue rolling (Can roll or Can't roll). The most famous classroom trait, and mostly a myth: identical twins often differ, and some people learn it with practice. Simplified model
- Tongue folding (Can't fold or Can fold). Folding the tongue tip back into a cloverleaf is taught as recessive (n). Simplified model
- Hitchhiker's thumb (Straight or Hitchhiker's). A thumb that bends back past 50 degrees is taught as recessive (s). Simplified model
- Hair on middle finger (Hairy or Bare). Hair on the middle section of the fingers is taught as dominant (M). Simplified model
- Hand clasping (Left on top or Right on top). Which thumb lands on top when you lace your fingers. Simplified model
- Arm folding (Left on top or Right on top). Which arm lands on top when you fold your arms. Simplified model
- Bent little finger (Bent or Straight). A little finger that curves toward the ring finger is taught as dominant (B). Simplified model
- Morton's toe (Longer 2nd toe or Shorter). A second toe longer than the big toe is taught as dominant (L). Simplified model
- Darwin's tubercle (Bump or No bump). A small bump on the upper rim of the ear. Simplified model
- Hair whorl (Clockwise or Counter). The swirl at the crown of the head. Simplified model
- Unibrow (Unibrow or Two brows). Brows that meet in the middle are linked to the PAX3 gene and are taught as dominant (U). Simplified model
- Eyelash length (Long or Short). Long lashes are taught as dominant (L). Simplified model
- Gap between front teeth (Gap or No gap). A gap between the top front teeth runs in families and is taught as dominant (G). Simplified model
- Dark or blond hair (Dark or Blond). Dark hair is taught as dominant (D). Simplified model
- Uncombable hair (Combable or Uncombable). Silvery, frizzy hair that stands straight out and cannot be combed flat.
- Wisdom teeth (All four or Some missing). About one in four people lacks at least one wisdom tooth. Simplified model
Senses & body
- Earwax (Wet or Dry). A single letter change in the ABCC11 gene decides it.
- Bitter taste (PTC) (Tastes it or Can't taste). Whether the test chemical PTC tastes bitter depends mostly on the TAS2R38 gene.
- Lactose as an adult (Tolerant or Intolerant). Most adults worldwide stop digesting lactose.
- Red-green color vision (Typical or Color-blind). These genes sit on the X chromosome.
- Handedness (Right-handed or Left-handed). About one person in ten is left-handed. Simplified model
- Cilantro tastes like soap (Soapy or Fresh). A smell-receptor gene, OR6A2, raises the odds of tasting soap a little. Simplified model
- Smelling asparagus pee (Smells it or Can't). Almost everyone makes the smell after eating asparagus, but not everyone can detect it. Simplified model
- Sneezing at bright light (Sneezes or No sneeze). The photic sneeze reflex runs in families like a dominant trait (A).
- Alcohol flush (Flushes or No flush). The ALDH2*2 variant (F) slows the breakdown of alcohol, so the face turns red.
- Caffeine speed (Slow or Fast). The CYP1A2 liver enzyme clears caffeine. Simplified model
- Sprint muscle protein (Has it or Lacks it). Two copies of the X version of ACTN3 mean fast muscle fibers lack alpha-actinin-3.
- Smelling androstenone (Smells it or Faint or none). Androstenone is a musky smell from pork and sweat. Simplified model
Blood
- Blood type (A, B, AB or O). A and B are codominant, so one copy of each gives type AB.
- Rh factor (Rh+ or Rh−). One working RHD gene (D) makes a person Rh positive.
- Secretor status (Secretor or Non-secretor). Secretors (Se) release their ABO blood-type markers into saliva and other fluids.
- MN blood group (M, MN or N). M and N are codominant, so one copy of each gives type MN.
- Duffy blood group (Duffy + or Duffy −). Two silent copies (Fy0) mean red cells lack the Duffy marker, which protects against one malaria parasite.
- Kell blood group (K+ or K−). K positive is the less common type.
- Bombay blood type (Usual or Bombay). Two silent copies of FUT1 (h) remove the H marker that A, B and O are built on.
For learning and fun, not medical advice. Anyone left unset counts as a typical person. Population figures are rough averages and vary a lot between ancestries.
Made by Jove Kane. Questions or ideas? Use the contact form.