Quick Answer
You can usually find out your baby’s sex at the 20-week anomaly scan (18 to 21 weeks) on the NHS. Private clinics can sometimes tell as early as 16 weeks with ultrasound, and non-invasive prenatal testing (NIPT) blood tests can determine sex from 10 weeks — though NIPT is not routinely offered on the NHS purely to find out the sex. [Tommy’s](https://www.tommys.org/) has a helpful guide to what happens at each pregnancy scan if you want to read more.
The Standard NHS Timeline
In the UK, the NHS offers two routine ultrasound scans during pregnancy:
- Dating scan — around 8 to 14 weeks (usually 12). This confirms the due date, not the sex.
- Anomaly (20-week) scan — between 18 and 21 weeks. This is when most parents first learn the sex.
At the anomaly scan, the sonographer’s main job is checking the baby’s development — heart, brain, spine, and other organs. Finding out the sex is a bonus, not the purpose, so it’s not guaranteed. The [NHS](https://www.nhs.uk/pregnancy/your-pregnancy-care/ultrasound-scans/) notes that the anomaly scan’s primary purpose is to check for physical abnormalities.
Can You Find Out Earlier?
Private ultrasound (16+ weeks)
Private scanning clinics across the UK offer “gender reveal” scans from around 16 weeks. Accuracy at 16 weeks is good but not perfect — around 90–95% — and improves significantly by 18 to 20 weeks. Costs typically range from £40 to £80.
Important caveats:
- Clinics must still be registered and follow clinical guidance
- Some NHS sonographers and private clinics have policies against revealing the sex — ask beforehand
- Accuracy depends on the baby’s position; a wriggly baby can make it impossible
NIPT blood test (10+ weeks)
Non-invasive prenatal testing analyses fragments of the baby’s DNA in the mother’s blood. It can determine sex with over 99% accuracy from 10 weeks. In the UK, however, NIPT is generally only available:
- On the NHS — only for high-risk pregnancies (e.g. after combined screening shows elevated risk), and not offered purely for sex determination
- Privately — widely available from around £250–£450 at private clinics
Some parents order NIPT privately primarily to learn the sex early. That’s legal in the UK, though it’s worth knowing that UK guidance frowns on sex selection for non-medical reasons.
Other methods (not recommended)
- Amniocentesis/CVS — these diagnostic tests reveal the sex, but they’re invasive (small miscarriage risk) and never done just to find out the sex
- Old wives’ tales — heart rate, bump shape, cravings, and the Chinese gender chart have no scientific basis. They’re fun, not reliable
How Accurate Is the 20-Week Scan?
When the sonographer can get a clear view, accuracy at 18 to 21 weeks is 95–99%. Mistakes happen occasionally — usually when the baby is in an awkward position, or when the umbilical cord sits between the legs and mimics anatomy. If the view isn’t clear, a good sonographer will say “I can’t be sure” rather than guess.
NHS Policy: Will They Tell You?
Most NHS trusts will tell you the sex at the anomaly scan if you ask and the view is clear — but policies vary. Some sonographers prefer not to, because the scan’s purpose is medical and because incorrect guesses cause distress. Tips:
- Ask at the start of the scan whether they can check
- Don’t be disappointed if they can’t — the baby’s position may make it impossible
- If they won’t tell you, you can book a private scan instead
The baby’s cooperation matters more than anything: roughly 1 in 10 scans can’t determine the sex because of positioning.
Should You Find Out Early? Points to Consider
| Method | Earliest | Accuracy | Cost (UK) |
|—|—|—|—|
| Private ultrasound | 16 weeks | ~90–95% | £40–£80 |
| NHS anomaly scan | 18–21 weeks | 95–99% | Free |
| Private NIPT | 10 weeks | 99%+ | £250–£450 |
Reasons parents choose to find out: bonding, choosing a name, practical preparation, managing expectations in families with strong preferences.
Reasons parents wait: keeping a surprise, avoiding disappointment from wrong guesses, avoiding pressure from family opinions about “the right” sex.
There’s no medical reason to learn the sex early unless there’s a family history of a sex-linked genetic condition — in which case your midwife or GP will refer you appropriately. The charity [ARC (Antenatal Results and Choices)](https://www.arc-uk.org/) supports parents navigating screening decisions.
FAQ
How many weeks pregnant to find out if it’s a boy or girl?
The standard answer in the UK is 20 weeks (the anomaly scan, done at 18–21 weeks). Earlier options exist: private ultrasound from 16 weeks, or NIPT blood testing from 10 weeks. Most parents learn the sex at their free NHS scan.
Can the 20-week scan be wrong about gender?
Rarely, but yes. Accuracy is 95–99% with a clear view, but an awkward baby position or the umbilical cord can cause misidentification. Late-pregnancy scans are the most accurate, but even then, sonographers occasionally get it wrong.
Why won’t my NHS sonographer tell me the sex?
The anomaly scan exists to check your baby’s health, not to determine sex. Some trusts and individual sonographers decline to guess, partly to avoid the distress of wrong answers. You can always ask — many will tell you — or book a private scan if yours won’t.
Is NIPT available on the NHS to find out the sex?
NIPT is offered on the NHS in certain high-risk situations, but not as a routine way to learn the sex. If you want NIPT purely for early sex determination, you’ll need to go private (typically £250–£450). The NHS does offer NIPT where there’s a medical indication — your midwife can advise.
Do gender prediction myths work?
No. Foetal heart rate, the shape of your bump, food cravings, morning sickness severity, and lunar charts have all been studied or debunked — none predicts sex better than chance (50/50). Enjoy them as fun traditions, but don’t plan the nursery around them.
Conclusion
In the UK, expect to find out your baby’s sex at the NHS 20-week anomaly scan (18–21 weeks), free of charge. If you can’t wait, private ultrasound from 16 weeks or NIPT from 10 weeks are reliable earlier options. Whatever you choose, remember the scan’s main purpose is your baby’s health — the sex reveal is a happy extra.
