Fertility by Age Calculator — Conception Probability
Estimate the per-cycle and cumulative probability of conception at your age. Enter female age and the number of cycles you plan to try to see how research-based fecundability rates translate into real chances — and how IVF success rates compare.
years
cycles
Average monthly fecundability at age 30
- 1
Monthly fecundability rate
p = 18 % = 0.18Population estimate from Dunson et al. 2002 and SART data for this age group. - 2
Probability of not conceiving per cycle
1 − 0.18 = 0.82 - 3
Survival over 12 cycles
0.82^12 = 0.0924 - 4
Cumulative probability (12 cycles)
1 − 0.0924 = 90.8
How does this calculator work?
Monthly conception probability ranges from ~25% at age 20 to ~8% at 40, based on published cohort data. Cumulative probability over n cycles = 1 − (1 − p)^n. At 20% per cycle, 89% of couples conceive within 12 cycles. These are population averages for couples without identified fertility issues.
Formula
How this is calculated
Monthly fecundability — the probability of conceiving in a single menstrual cycle — declines gradually with female age. Values used here draw on large-sample cohort studies (Dunson et al. 2002, the NCHS, and SART national outcome data): roughly 22–25% per cycle in the early 20s, dropping to 8% around age 40 and 2% by the mid-40s. These are averages for couples with no identified fertility problems; individual variation is large.
For n cycles of trying, the cumulative probability of at least one conception is 1 − (1 − p)^n, the complement of failing in every cycle. The geometric distribution mean 1/p gives the expected number of cycles to conceive. IVF live-birth-rate estimates come from 2022 SART national data (live births per transfer for fresh own-egg cycles) and decrease sharply after age 37.
This tool gives population-level probabilistic context, not a medical prognosis. Fertility is influenced by male-factor issues (responsible for ~30% of infertility), underlying conditions such as endometriosis or PCOS, lifestyle, and chance. Couples who have been trying for 12 months (or 6 months if the female is over 35) without success are typically advised to seek evaluation from a reproductive endocrinologist.
Frequently asked questions
Fertility decreases gradually through the 20s and 30s, with a more pronounced drop after age 35. Monthly fecundability falls from about 22% in the late 20s to roughly 12% by 37, 8% by 40, and 2% by the mid-40s. These are averages — individual variation is substantial.
With a per-cycle rate of about 20%, roughly 64% of couples conceive within 6 cycles and 89% within 12. The geometric distribution mean is 1/p cycles, so at 20% that is about 5 cycles on average. Medical guidelines define infertility as 12 months of unprotected intercourse without conception (6 months if over 35).
No — it estimates female-age-based population fecundability and assumes no male-factor infertility. Male factor accounts for about 30% of infertility cases. For a complete assessment, both partners should be evaluated.
TG we-Calculate Editorial Team. (2026). Fertility by Age Calculator — Conception Probability [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/fertility-by-age-calculator
TG we-Calculate Editorial Team. "Fertility by Age Calculator — Conception Probability." TG we-Calculate. 2026. https://we-calculate.com/calculator/fertility-by-age-calculator.
TG we-Calculate Editorial Team, "Fertility by Age Calculator — Conception Probability," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/fertility-by-age-calculator
@misc{wecalculate_fertility_by_age_calculator, title = {Fertility by Age Calculator — Conception Probability}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/fertility-by-age-calculator}}, year = {2026}, note = {TG we-Calculate} }
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