Chance of conceiving by age
Enter your age and how long you have been trying. This tool gives your chance of conceiving in the coming cycle, in the next six months and in the next twelve, alongside the published figures it is built from. Most couples who have been trying six months and are worried are, statistically, entirely ordinary.
Chance of conceiving by age
No sign-up · PrivateFemale age is the strongest single predictor in every published cohort. Male age matters too, but less predictably.
Count only months with regular unprotected sex. Enter 0 if you are about to start — the answer for month zero is the published one-year figure.
Used only to convert months into attempts, because the published tables count CYCLES, not months. Longer cycles mean fewer chances per year.
Chance of conceiving in the next 12 months
After 6 months already, for ages 30 to 34. Lower than the odds you started with, and still better than even.
Chance in the next 6 months: 48%
Measured per-cycle chance at your age: 20.9% on average across a year of trying — measured in 247 women aged 32 to 33 (Steiner & Jukic, 2016)
Chance in this coming cycle: 12% — among couples still trying after 7 cycles. Lower than cycle one because the group you are now in contains more couples who will need help, not because anything has changed in you.
Where you are now: About 76% of couples in the 30 to 34 band have conceived by 7 cycles. The other 24% are exactly where you are.
NICE NG257 Table 1, ages 30 to 34: 86% conceive within 12 cycles and 94% within 24 — assuming sex twice a week
Flat-rate equivalent: 15.1% a cycle would produce that one-year figure on its own
When guidelines say to ask for help: Under 35, ACOG suggests an infertility evaluation after 12 months of regular unprotected sex without a pregnancy.
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How this is calculated
FormulaHow these odds are calculated
Step 1 — the published anchors. For ages 19 to 39 the tool uses NICE guideline NG257 (published 31 March 2026, replacing the withdrawn CG156), Table 1, reproduced from Dunson, Baird and Colombo (Obstetrics & Gynecology, 2004) and assuming vaginal intercourse twice a week: 92% conceive within 12 cycles and 98% within 24 at ages 19–26; 87% and 95% at 27–29; 86% and 94% at 30–34; 82% and 90% at 35–39. NG257 recommendation 1.4.1 adds that over 80% of couples in the general population conceive within one year where the woman is under 40, and that of those who do not, about half do so in the second year.
NG257 publishes no equivalent intercourse table above 39, so above that age this tool reports — unmodelled — the cohort NICE itself uses for its Figure 1: Steiner and Jukic (Fertility and Sterility, 2016), 960 women aged 30 to 44 with no known fertility problem. Their Table 2 gives average per-cycle fecundability and cumulative rates at 6 and 12 cycles: 19.5% / 77% / 87% at 30–31; 20.9% / 76% / 88% at 32–33; 16.2% / 71% / 82% at 34–35; 14.5% / 69% / 76% at 36–37; 13.2% / 62% / 71% at 38–39; 8.6% / 47% / 54% at 40–41; and 6.6% / 29% / 48% at 42–44. Above 44 the tool gives no number, because no prospective cohort extends there.
Step 2 — the month-by-month curve. Couples differ, so cumulative conception is not geometric; the couples still trying at month 12 are enriched for lower fecundability and the curve flattens. The tool uses the standard beta-geometric model, in which per-cycle probability varies between couples as a Beta(a, b) distribution, so the chance of not having conceived after n cycles is S(n) = ∏k=0..n−1 (b + k) / (a + b + k) and the chance of conceiving in cycle n+1 given you have not yet is a / (a + b + n). Fitting to the two NICE anchors gives a = 3.1701, b = 8.8205 for 19–26; 1.8828 and 5.7187 for 27–29; 1.5749 and 4.5582 for 30–34; 0.9744 and 2.5061 for 35–39.
The check. Reproducing NICE at 12 and 24 cycles is exact by construction and proves nothing. The real test is a number the fit was never given: Dunson 2004 separately reports that among couples who had not conceived in 12 cycles, conception rates within an additional 12 cycles ran from 43% to 63% depending on age. These curves independently return 44% for 35–39, 57% for 30–34 and 62% for 27–29.
Step 3 — the per-cycle figure. The model's fitted first-cycle mean is not reported, and the forward per-cycle line is suppressed for the first two cycles: two anchors cannot cleanly separate the average couple's monthly chance from the spread between couples, and there the fit stops ordering correctly by age. Reported instead are the measured figures — ACOG's 'around 1 in 4' for healthy couples in their 20s and early 30s and 'around 1 in 10' by age 40, plus Steiner's per-cycle averages — and the flat-rate equivalent, 1 − (1 − C12)1/12, which is 19.0%, 15.6%, 15.1% and 13.3% a cycle for the four NICE bands.
One cycle is not one month. Every published table counts cycles. On a 35-day cycle you get about 10.4 attempts a year rather than 12, so the tool converts months into cycles before it calculates.
What the guidelines actually say
NICE guideline NG257, which replaced the withdrawn CG156 on 31 March 2026, states that over 80% of heterosexual couples in the general population will conceive within one year where the woman is under 40 and they are having regular unprotected vaginal sex, and that of those who do not, about half will do so in the second year — a cumulative rate above 90%. Its Table 1 splits that by age: 92% within a year at 19 to 26, 87% at 27 to 29, 86% at 30 to 34 and 82% at 35 to 39, rising to 98%, 95%, 94% and 90% respectively by two years.
Those numbers come from Dunson, Baird and Colombo (2004) and assume intercourse twice a week. They describe couples with no known fertility problem, which is the right comparison group for most people reading this and the wrong one for some. If you have very irregular or absent periods, known endometriosis or PCOS, previous pelvic surgery or infection, or a partner with a known sperm issue, these tables are not about you and the clock should start earlier.
Per cycle, not per year
The figure most people want is the monthly one. ACOG puts healthy couples in their 20s and early 30s at 'about 25 to 30 percent in any single menstrual cycle', which starts to decline in the early 30s and declines more rapidly after 37; by age 40 the chance is 'less than 10 percent per menstrual cycle'.
Steiner and Jukic measured the same quantity prospectively in 960 women aged 30 to 44, and their figures line up: average fecundability of 19.5% at ages 30 to 31, 20.9% at 32 to 33, 16.2% at 34 to 35, 14.5% at 36 to 37, 13.2% at 38 to 39, 8.6% at 40 to 41 and 6.6% at 42 to 44. ACOG's 'around 1 in 10 by 40' and Steiner's 8.6% at 40 to 41 are two different studies, two different decades and effectively the same answer.
Why the odds seem to fall the longer you try
This is the most misread statistic in fertility, and understanding it changes how the wait feels. Couples differ enormously in monthly chance. The ones with the highest chance conceive first and leave the group. What remains is a slower-conceiving mixture, so the average monthly rate among couples still trying falls month by month even though nothing about any individual has changed.
This is selection, not deterioration. It also means the corollary is true: a year without a pregnancy is not a forecast of the next year. Dunson's own paper reports that among couples who had not conceived in 12 cycles, 43% to 63% did so within another 12, depending on age. NICE says the same thing in plain words — of those who do not conceive in the first year, about half do so in the second.
Where the 35 to 39 band hides a slope
NICE's single 82% figure for ages 35 to 39 averages five years that are not alike. The Steiner cohort NICE cites in its own Figure 1 measured 82% at 12 cycles for ages 34 to 35, but 76% for 36 to 37 and 71% for 38 to 39. If you are 38 or 39, the lower figure is the better estimate for you. That slope is exactly why the referral threshold drops from twelve months to six at 35.
After 40, the evidence thins out
NICE publishes no intercourse table above 39, and this tool does not extend one. What exists is the Steiner cohort, and it is honest about its own limits: the 40-to-41 band rests on 37 women (54% within 12 cycles, 95% confidence interval 37 to 72%) and the 42-to-44 band on 14 (48%, interval 24 to 80%). Those intervals are wide because the samples are small, and any tool quoting a single tidy number at these ages is inventing precision.
The shape is still informative. Median time to pregnancy in that cohort was three months for women under 38, four months at 38 to 39, eight months at 40 to 41, and longer than twelve months at 42 and over. That is a lengthening, not a wall. One finding shifts the estimate more than a birthday does: women who had been pregnant before did substantially better at every age, and over 40 those who had never conceived were about half as likely to conceive within 12 cycles as those with a previous pregnancy. Above 44, no prospective cohort exists at all, and ACOG's position is that natural conception is unlikely.
When to ask for help
ACOG recommends an infertility evaluation after 12 months of regular unprotected sex if you are under 35, after 6 months if you are older than 35, and a conversation with an ob-gyn straight away if you are older than 40. Those thresholds are not judgements about patience. They are about how much time is reasonable to spend before finding out whether there is something treatable — and most causes of infertility are treatable, including many where no cause is ever identified.
The advice to ignore
There is no good evidence that ordinary stress prevents an otherwise fertile couple from conceiving, and telling someone their distress is the cause of their infertility is both unkind and unfalsifiable. 'Just relax' cannot be disproved, which is exactly what makes it useless. The reason most couples conceive in the second year is not that they calmed down. It is that fertility is a probability per cycle, and cycles keep coming.
Sources
- Fertility problems: assessment and treatment - NICE guideline NG257, sections 1.4 and 1.5 — National Institute for Health and Care Excellence (published 31 March 2026, replacing the withdrawn CG156), accessed
- Increased infertility with age in men and women — Obstetrics & Gynecology (Dunson DB, Baird DD, Colombo B, 2004;103:51-6), accessed
- Impact of female age and nulligravidity on fecundity in an older reproductive age cohort — Fertility and Sterility (Steiner AZ, Jukic AMZ, 2016;105:1584-8), accessed
- Having a Baby After Age 35: How Aging Affects Fertility and Pregnancy (FAQ) — American College of Obstetricians and Gynecologists, accessed
- Evaluating Infertility (FAQ) — American College of Obstetricians and Gynecologists, accessed
- Trying to get pregnant — NHS, accessed