Frequently Asked Questions

TraitGen is a free genetics education platform with 39 interactive calculators and 45+ articles. Each calculator lets you enter parental and grandparental traits and see the probability of those traits being inherited, based on peer-reviewed genetic inheritance models. Everything runs in your browser with no sign-up required.

TraitGen was founded by Shahzad Arsi, a science writer and independent researcher based in India specialising in genetics, heredity, and molecular biology. You can connect with him on LinkedIn.

Yes, completely free. All 39 calculators, all articles, and all educational content are free with no registration, no subscription, and no hidden costs. TraitGen is funded by display advertising via Google AdSense.

No. TraitGen is an independent educational project. It is not affiliated with, endorsed by, or associated with any academic institution, healthcare provider, government body, or commercial organisation. All content is produced independently by the TraitGen team.

The calculators use established genetic models drawn from peer-reviewed research. Simple traits like earlobe type use Mendelian Punnett square logic. Complex traits like eye colour, height, and skin tone use polygenic models that account for contributions from both parents and grandparents. Results are probability estimates, not guarantees. Actual outcomes depend on random chromosome sorting at conception.

Grandparent data significantly improves prediction accuracy for many traits. For example, a brown-eyed parent with a blue-eyed grandparent is statistically more likely to carry the recessive blue-eye allele than a brown-eyed parent whose parents are also brown-eyed. Grandparent inputs are always optional but narrow the probability range meaningfully.

The calculator format reflects the nature of the trait being predicted. Traits with discrete outcomes (eye colour, blood type, dimples) use probability bar charts. Developmental traits that change over time (baby eye colour timeline, melanin development, baby growth) use milestone timelines alongside probability outputs to show both the likely outcome and when to expect it.

Yes. Every calculator has a Download PDF button (which prints the result page to PDF) and a Share button with options for WhatsApp, X (Twitter), Facebook, and Copy Link. These appear after you press Calculate.

A dominant trait is expressed when at least one copy of the dominant allele is present. A recessive trait is only expressed when both alleles are the recessive version (one from each parent). For example, brown eye colour is dominant over blue, so a person only needs one brown-eye allele to have brown eyes. Blue eyes require two copies of the recessive allele. Many traits on TraitGen follow this pattern, though most are more complex than simple dominant-recessive.

A polygenic trait is influenced by many genes simultaneously, each contributing a small effect. Height, skin tone, hair colour, and face shape are all polygenic. Because the outcome reflects the combined effect of many variants inherited randomly from both parents, the result is a continuous spectrum rather than two or three distinct categories. This is why the probability bars in our calculators show a range of possible outcomes rather than a single answer.

Because most people carry hidden (recessive) alleles that are not expressed in their own appearance. A brown-eyed parent can carry a blue-eye allele. A straight-haired parent can carry a curly-hair allele. If both parents carry the same recessive allele, there is a 25% chance per child of inheriting two copies and expressing the hidden trait. This is why traits can appear to skip generations.

Incomplete dominance occurs when neither allele is fully dominant over the other, and the result is an intermediate expression. Hair texture is a classic example: a parent with very straight hair and a parent with very curly hair often produce a wavy-haired child rather than clearly one or the other. Eye colour also shows some incomplete dominance between green and blue. Our calculators account for incomplete dominance where it is scientifically established.

Eye colour is typically stable by 12 to 18 months. Many babies are born with blue or grey eyes because melanin production has not yet activated. As melanocytes respond to light exposure in the first months, colour shifts toward the genetically programmed shade. Eyes that are dark brown at birth almost always remain brown. Eyes that are blue or grey at birth may darken to green, hazel, or brown depending on parental genetics. See the Baby Eye Colour Timeline calculator.

Melanin production is not fully active at birth. A baby inherits the genetic capacity for melanin from both parents, but melanocyte cells need time and light exposure to activate to their programmed production rate. Most babies, including those with darker-skinned parents, appear lighter at birth than their final skin tone will be. The ear tip is a useful early indicator of eventual depth of pigmentation. See the Melanin Development Tracker.

Yes, substantially in the first two years. Eye colour shifts as melanin activates (months 1 to 18). Skin tone deepens as melanocytes reach full production (months 1 to 18). Fine baby hair falls out and regrows, often in a different colour and texture (months 3 to 12). Face shape changes dramatically as the skull grows forward during the first year. Most final traits are established by age 2 to 3, though face shape continues to mature through adolescence.

Yes. The calculators work equally well for existing children and unborn babies. If your child is already born and you want to understand why they have a particular trait or how it might change, the calculators and science sections explain the genetics behind what you are observing. The Baby Eye Colour Timeline and Melanin Development Tracker are specifically designed for tracking post-birth development.

The Blood Type calculator uses ABO codominance and Rh factor dominant inheritance. It calculates the probability of each of the 8 possible blood type combinations (A+, A-, B+, B-, AB+, AB-, O+, O-) based on parental blood types. If you know whether a parent is homozygous (AA or BB) or heterozygous (AO or BO), you can enter this for higher accuracy. The calculator uses global Hardy-Weinberg allele frequency estimates for parents where genotype is unknown. See Blood Type Predictor.

The Due Date calculator uses Naegele's rule: LMP date plus 280 days (40 weeks) for standard 28-day cycles. For cycles other than 28 days, it adjusts the result accordingly. It also supports calculation from a known conception date (266 days) and IVF transfer dates (Day 3: 263 days, Day 5 blastocyst: 261 days). The calculator shows current gestational week, trimester, and key milestone dates. Always confirm your due date with your doctor or midwife. See Due Date Calculator.

The Baby Face Generator uses the Anthropic Claude AI to generate a personalised description of your baby's likely appearance based on both parents' eye colour, hair colour, skin tone, and face shape. It is educational and for entertainment. The parent trait data you enter is sent to the Anthropic API to generate the description. No personally identifying information is collected or stored. See Baby Face Generator.

Because both the Chinese Lunar Calendar method and the Shettles Method have been tested in multiple scientific studies and found to be no more accurate than a coin flip (approximately 50%). Biological sex is determined at fertilisation by which sperm reaches the egg first: an X-bearing sperm produces a girl, a Y-bearing sperm produces a boy. This is a random event that no folk method can reliably influence or predict. We include the calculator because it is widely searched and culturally significant, but we are committed to scientific honesty about its limitations.

Yes. All calculations run entirely in your browser using JavaScript. Nothing you enter into any calculator is sent to our servers, stored in a database, or shared with any third party. When you close or refresh the page, all entered data is gone. We genuinely cannot see, access, or retrieve anything you type into the calculators.

Yes, for two purposes: Google Analytics (anonymised traffic analysis) and Google AdSense (advertising). We also set one first-party cookie to remember your cookie consent preference. Your calculator inputs are never stored in cookies. You can manage your preferences on the Cookie Settings page.

Yes. You can decline advertising and analytics cookies on the Cookie Settings page or through your browser settings. The calculators function entirely without cookies and will still work fully if you decline tracking. Only essential cookies (storing your consent preference) are strictly necessary.

No. TraitGen does not collect, sell, or share personal data. We do not have a database of user information to sell. The only data that flows through third-party services is anonymised analytics traffic data via Google Analytics and ad-serving information via Google AdSense, neither of which contains personally identifiable information tied to your calculator inputs.

No. All calculators on TraitGen are for educational purposes only. Results are probability estimates based on simplified genetic models, not clinical assessments. They should not be used to make any medical, prenatal, or health-related decisions. If you have concerns about hereditary conditions, genetic disorders, or prenatal health, please consult a qualified doctor, obstetrician, or certified genetic counsellor.

A genetic counsellor is a healthcare professional with specialised training in medical genetics and counselling. They can help with risk assessment for hereditary conditions, interpretation of genetic test results, family planning decisions when there is a known genetic condition in the family, and understanding the implications of a genetic diagnosis. You should consider seeing a genetic counsellor if you have a family history of hereditary conditions, if you or your partner have a genetic disorder, or if prenatal screening has flagged a concern.

The due date calculator uses the standard Naegele's rule used in obstetrics globally, and the baby growth chart uses official WHO Child Growth Standards. Both are established clinical tools when used correctly. However, due dates are estimates with inherent uncertainty, and growth percentiles should always be interpreted in context by a healthcare professional. Never use these calculators as a substitute for antenatal care or paediatric consultations.

No. TraitGen calculators cover cosmetic and physical trait inheritance only: eye colour, hair colour, height, face shape, and similar non-medical traits. We deliberately do not cover disease risk prediction, carrier status for genetic conditions, or health-related genetic testing. These are medical matters that require proper clinical assessment by qualified genetic healthcare professionals, not educational web calculators.

TraitGen works in all modern browsers including Chrome, Firefox, Safari, and Edge on desktop and mobile. The calculators use standard JavaScript and CSS that is supported by any browser released in the past 5 years. Internet Explorer is not supported. For the best experience, we recommend a current version of Chrome or Firefox.

First try refreshing the page. If a calculator still does not work, try clearing your browser cache or opening the page in a private or incognito window. Some ad-blockers or privacy extensions can interfere with page functionality. If the issue persists, please contact us with the calculator name and your browser version.

Not currently. Our calculators are not designed for embedding on third-party sites. If you are interested in a partnership or educational use, please get in touch and we can discuss options.

Not currently. TraitGen is a mobile-optimised website that works well on smartphones and tablets through your mobile browser. All calculators are fully functional on mobile. A dedicated app may be considered in future based on user demand.