The legendary Chinese gender calendar

Chinese Gender Predictor —
Boy or Girl?

Free instant prediction from the centuries-old Chinese gender calendar. Then see all 5 methods agree — or disagree — in the BabyPeek app.

Instant No sign-up On-device For fun, not medical

Try the calendar

Two dates. One instant guess.

Please fill in both dates to get your prediction.

This is the lite version.

The calendar is just one guess. BabyPeek runs Nub, Ramzi & Skull theory on your actual ultrasound photo, plus the Chinese calendar and a playful Photo Pick, shows one majority verdict, and turns it into a shareable reveal.

Download on theApp Store

Five ways to peek

The methods, side by side

Chinese Calendar

Birth date + month

Nub Theory

Angle of the dangle

Ramzi Theory

Left or right

Skull Theory

Brow & jaw

Photo Pick

In the app

One method can be a coin flip. Five together is a verdict. See how the methods compare →

How it works

From a hunch to a reveal in three taps

1

Enter or upload

A birth date for the calendar, or your 12-week scan for nub, ramzi & skull theory.

2

See every method

Each gives boy or girl plus an honest label for how much evidence is behind it — no fake certainty, ever.

3

Reveal & share

Resolve purple into blue or pink, save a card, and tell your whole family.

Why trust this

Honest by design

We'd rather tell you it's a coin flip than sell you false certainty.

Based on real studies

Our accuracy figures come from primary research, not competitors' blog posts — read alongside the folklore.

Efrat et al. 1999 & 2006 · Villamor et al. 2010 (n=2,840,755)

Honest about accuracy

Folk methods land around a coin flip (~50%); only the nub, read from about 12 weeks, does much better. When something is a guess, we call it a guess — clearly.

Every tool says how strong its evidence is

Private by default

In the BabyPeek app your scan is read on your device. Your ultrasound is never uploaded to a server.

On-device processing
BP Written by the BabyPeek editorial team from published studies. How we research and write →

Photo teaser

Have a 12-week scan? Try the Nub guesser.

Drop in your dating-scan photo and watch Peek take a look. The web teaser shows you there's an answer there — the full nub-angle read happens in the app.

Unlock the full read — nub angle, all 5 methods, and one majority verdict.

No waiting for a human reader — it's instant in BabyPeek.
Open in BabyPeek
Drop your 12-week scan [ click or drag — png / jpg · stays on your device ]
I can see it… 😄 Hidden until you reveal in the app Unlock in BabyPeek

Learn the methods

Guides for every theory

Nub

How to read the nub at 12 weeks

The angle of the dangle, explained with boy-vs-girl examples.

Read the guide →
Ramzi

Ramzi theory: left or right?

What placenta location is said to mean — and why sides flip on scans.

Read the guide →
Skull

Skull theory markers

Brow ridge, jaw and forehead slope — the cues people look for.

Read the guide →
Chinese

The Chinese gender chart for 2026

How lunar age and lunar month map to boy or girl.

Read the guide →
Ultrasound

Turtle vs hamburger sign

The two signs sonographers look for at the 18–20 week anatomy scan.

Read the guide →
Compare

Boy nub vs girl nub

How to spot the difference — examples and the angle that matters.

Read the guide →

Got your answer?

Make the moment unforgettable

Turn your reveal into a shareable card — or plan the whole party. Purple resolves into blue or pink, just like the moment you've been waiting for.

Questions

The honest answers

It's about as accurate as a coin flip — studies put it near 50%. It's a centuries-old tradition, fun to try, but not science. For more signals, the BabyPeek app combines five methods, including a nub-angle measurement on your own scan.
The genital tubercle (the "nub") is usually readable on a clear profile shot at around 12–13 weeks. At 11 weeks it's still unreliable (about 70% correct in the original study) and earlier it's too underdeveloped, and the angle needs a good mid-sagittal view to judge. More on nub theory →
The theory claims a right-sided placenta means boy, left means girl. Evidence is weak, and scans can be mirrored depending on the probe — which flips the result. Treat it as one fun signal among several. Read about Ramzi →
Yes. In the first trimester it's less reliable (studies average about 85%); by the 18–20 week anatomy scan it's high but not perfect — position, cord and swelling can fool the eye. A second look or a later scan resolves most uncertainty.
No. Everything here is for entertainment only and is not medical advice or diagnosis. For anything about your pregnancy, talk to your doctor or midwife.
This page answers once, with one folk method. The app runs Nub, Ramzi and Skull theory on your real ultrasound, plus the Chinese calendar and a playful Photo Pick, shows one majority verdict with an honest evidence label for each method, and turns it into a shareable reveal.

Sources

  1. Villamor E, Dekker L, Svensson T, Cnattingius S. Accuracy of the Chinese lunar calendar method to predict a baby's sex: a population-based study. Paediatr Perinat Epidemiol. 2010;24(4):398–400. PubMed
  2. Efrat Z, Perri T, Ramati E, Tugendreich D, Meizner I. Fetal gender assignment by first-trimester ultrasound. Ultrasound Obstet Gynecol. 2006;27(6):619–21. PubMed
  3. P18.17: The role of placental location assessment in the prediction of fetal gender. Ultrasound Obstet Gynecol. 2010 (conference abstract, 277 pregnancies). Source
  4. Efrat Z, Akinfenwa OO, Nicolaides KH. First-trimester determination of fetal gender by ultrasound. Ultrasound Obstet Gynecol. 1999;13(5):305–7. PubMed
  5. Amankona E et al. Effectiveness of prenatal ultrasound in fetal sex identification: a systematic review and meta-analysis. J Ultrasound. 2025. PubMed

Written by the BabyPeek editorial team from the studies above. How we research and write. For entertainment, not medical advice.

Boy or girl? Take your first peek today.

Five methods · one majority verdict · a shareable reveal.

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