Know your cycle.

Tap the day your period started. Your next period and fertile days show up in colour.

How the estimates work. Your cycle runs from the first day of one period to the first day of the next. You set how long yours is, so the calendar works from your first entry. Log a few more and the cycle length switches to your own measured average.

Period length starts at 5 days. Change it in Settings with Period lasts; a 3-day period and a 7-day one shade the calendar differently.

Fertile window: ovulation is estimated 14 days before your next period (the ACOG and NHS calendar method). The window covers the 5 days before it plus ovulation day itself.

Not birth control. These dates are an estimate, not birth control. Ovulation shifts with stress, illness, travel and sleep. Do not rely on this to avoid pregnancy. Around 12 to 24 in every 100 women relying on calendar methods get pregnant within a year. A polyclinic or GP can talk you through what works.

Irregular cycles get a range instead of one date once you log a few, because one confident date would mislead you.

Private. Nothing you tap here is sent anywhere. It is saved in this browser, on this phone, and we never see it. Clearing your browser data erases it.

When to see a doctor

• Soaking a pad or tampon every hour. Bleeding this heavy for several hours in a row needs to be checked.
• Bleeding longer than 7 days. A period that keeps going past a week is worth a consultation.
• Bleeding between periods, or after sex. Spotting outside your period should always be looked at.
• Pain that stops you working or sleeping. Period pain that painkillers do not touch is not something to endure quietly.
• No period for 3 months, and you are not pregnant. Missing several cycles has many causes and most are treatable.
• Cycles shorter than 21 or longer than 35 days. Especially if this is new for you.
• Trying to conceive for over a year with no result. Six months if you are over 35. Both partners should be checked.

Where to go in Singapore

• Any polyclinic: Subsidised GP care across Singapore. Walk in or book via the HealthHub app. Cheapest first stop for period problems.
• KK Women's and Children's Hospital: Specialist women's health. You usually need a GP or polyclinic referral first.
• HealthServe: Low-cost medical care and counselling for migrant workers.
• HOME (Humanitarian Organisation for Migration Economics): Free help for domestic workers, including getting to medical care.