Trying for a baby usually starts with one simple question: when am I fertile? Tymi estimates your fertile window and likely ovulation day from your period dates, lays your cycle out on a calendar and lets you log symptoms, mood and sleep. The maths stays on your device, with no account or ads — and the day the test is positive, the same profile switches to pregnancy tracking.
| Cycle length | Estimated ovulation | Estimated fertile window |
|---|---|---|
| 26 days | around day 12 | day 7 to day 12 |
| 28 days | around day 14 | day 9 to day 14 |
| 32 days | around day 18 | day 13 to day 18 |
Frequently asked questions
How do I work out my ovulation date?
Ovulation usually happens about 14 days before your next period, not 14 days after the last one: on a 28-day cycle that is around day 14, on a 32-day cycle around day 18. Tymi uses the average length of your recent cycles to estimate the day and refines it with every period you log.
How long is the fertile window?
About six days: the five days before ovulation and ovulation day itself, because sperm can survive up to five days and the egg about 24 hours. Intercourse in the two or three days before ovulation matters most. It is a statistical estimate — never a method of contraception.
When should I see a doctor if it takes time?
Common guidance is to seek advice after twelve months of trying without contraception under 35, and after six months from 35 — sooner if cycles are very irregular, very long or absent. A cycle history logged in Tymi is a useful starting point for that appointment.
Can cycle tracking be used as contraception?
No, and Tymi does not offer it as one. The estimate comes from the average of your past cycles, not from a measurement taken on the day. For contraception, speak to a health professional.
What if my cycles are irregular?
Log them anyway: the history is what carries weight in a consultation. The estimate becomes less precise, and Tymi shows it for what it is — an estimate, never a certain date.
When is it called infertility?
WHO defines it as the failure to achieve a pregnancy after twelve months or more of regular unprotected intercourse. The NHS suggests seeking advice earlier from 35, or if cycles are very irregular or absent.
This page gives general information. Tymi is not a medical device and does not replace advice from a midwife, doctor or pediatrician.
Sources
Sources checked on 2026-09-27.