Ovulation calculator
Estimate when you are most likely to ovulate and which days give the best chance of conceiving, based on your cycle length.
How this is calculated
The luteal phase, between ovulation and your next period, is relatively fixed at about 14 days for most people. The follicular phase before ovulation is the part that varies. So rather than assuming day 14, we count backwards: ovulation is estimated at cycle length minus 14 days from the start of your last period.
The fertile window shown covers the five days before ovulation plus ovulation day itself, because sperm can survive several days in the reproductive tract while an egg is viable for roughly a day after release.
Why this is an estimate and not a schedule
Ovulation timing varies between cycles even for people with regular periods, and stress, illness, travel, and sleep disruption all shift it. Calendar prediction is the least precise of the available methods. Ovulation predictor kits, basal body temperature tracking, and cervical mucus observation all give better real-time information about a specific cycle.
When to talk to someone
General guidance is to seek advice after twelve months of trying if you are under 35, or six months if you are 35 or over. Seek advice sooner if your cycles are very irregular or absent, or if you have a known condition affecting fertility. This is a conversation worth having earlier rather than later.
If you already have a positive test, try the due date calculator.