Per cycle, then compounded
The starting number is fecundability: the chance of conceiving in one cycle of well-timed sex. Population studies put it at roughly a quarter in the early twenties and a tenth by forty. Chances over six or twelve months are simply that per-cycle figure compounded: if each cycle is an 18% chance, twelve cycles give about 90%. This is why most healthy couples conceive within a year even though any single month feels like a coin toss weighted against them.
What moves the needle at any age
Timing dominates. Sex in the two days before ovulation carries most of the chance, so the best time to get pregnant calculator is worth using every cycle. Cycle regularity, ovarian reserve (see the AMH calculator), and sperm quality account for most of the difference between people of the same age. If you have been trying for the length of time shown for your age, an assessment is simple: cycle-day blood tests, an ultrasound, and a semen analysis.
Frequently asked questions
What are my chances of getting pregnant at my age?
For couples with no known fertility problem and well-timed sex, the average per-cycle chance is roughly 25% in the early twenties, about 20% at 30, 14% at 35, 10% at 38 to 40, and under 5% by 43. Over a year those compound to about 90% under 30, around 80% at 35, and roughly 50% at 40.
Why does fertility fall with age?
Egg number and egg quality both decline. A person is born with all their eggs; the count falls steadily and the proportion with chromosome errors rises, especially after 35, which lowers the chance of conception and raises the chance of miscarriage. Sperm quality also declines with age but more gradually.
How long should I try before seeing a doctor?
Under 35, guidelines suggest a fertility assessment after 12 months of trying. From 35 to 39, after 6 months. At 40 and over, after 3 months or straight away. Go sooner at any age if you have irregular or absent periods, known endometriosis or PCOS, a history of pelvic infection, or a partner with a known sperm issue.
Are these numbers a prediction for me?
No. They are population averages. Individual fertility varies enormously at every age, and factors like cycle regularity, ovarian reserve (AMH), tubal health, and sperm quality matter as much as the calendar. A fertility assessment replaces averages with your own numbers.
Does the male partner's age matter?
Yes, though less steeply. Sperm count, motility and DNA quality decline gradually from the late thirties, and paternal age over 40 to 45 is linked with slightly longer time to conception and some increased risks. The calculator uses the egg-providing partner's age because it dominates the numbers.
These calculators give estimates based on cycle averages and standard formulas. They are for general information only and are not medical advice. For anything concerning your health or pregnancy, talk to a qualified healthcare provider.