The fertility by age calculator above is a lookup table with arithmetic attached. It reports the per-cycle conception rate the American College of Obstetricians and Gynecologists publishes for two anchor ages, the miscarriage rate a large Danish national register study reported by age band, and the Down syndrome rate ACOG lists at five specific maternal ages. Every figure on the page comes from one of those two sources, and the page names which one supplied each number.
Arb Digital publishes this because the figures are genuinely hard to find in one place and are constantly misreported, and because the most important thing about them is the thing most articles bury. A population rate describes what happened across hundreds of thousands of people. It says nothing about any one of them. Two people the same age can have completely different fertility, and the published rate is the average of a very wide distribution, not a forecast for the person reading it. This page cannot tell you whether you will conceive, how long it will take, or whether anything is wrong. Those are questions for a fertility specialist or an obstetric provider, and this tool is not a step on the way to answering them.
What This Fertility by Age Calculator Does
It does three things, all of them lookups. It reports the per-cycle probability of conception published for the age you enter. It reports the miscarriage rate published for the age band you fall into. And it reports the Down syndrome rate published at the nearest of the five ages ACOG lists.
It also computes one derived number: the cumulative probability of conceiving across a run of cycles, under a constant-rate geometric model. That figure is arithmetic performed by this page, not a published statistic, and the page labels it as such. Its assumptions are stated in full further down, because they are the sort of assumptions that make a number look more solid than it is.
What the page does not do is score you, rank you, assess a risk for you, or suggest a course of action. It offers no view on when to start trying, whether to freeze eggs, when to seek an evaluation, or what any result means for a plan. Those are clinical and personal decisions, and a calculator that knows only your age has no business having an opinion about any of them.
How to Use It
- Enter an age. Use age at conception rather than age now if you are looking at a future scenario, because that is how the register study classified its data.
- Read the hero figure with its label. It tells you whether the number is a published anchor or a value this page interpolated between two anchors. That distinction matters more than the digits.
- Set the number of cycles if you want the cumulative view. Twelve is conventional because clinical definitions of infertility are framed around a year of trying.
- Note the study population beside each rate. A Danish register from 1978 to 1992 and a US clinical FAQ are describing different populations in different eras, and neither was assembled to describe you.
- Take questions to a clinician. That is the whole intended use: to arrive at a conversation having read the published figures rather than a headline about them.
The Published Figures and Where They Come From
Per-cycle conception. ACOG's patient FAQ Having a Baby After Age 35: How Aging Affects Fertility and Pregnancy states that for healthy couples in their 20s and early 30s, around 1 in 4 women will get pregnant in any single menstrual cycle, and that by age 40 around 1 in 10 will get pregnant per cycle. Those are the only two per-cycle figures the source gives. This page uses 25 percent up to age 32 and 10 percent at age 40, and between those ages it draws a straight line and says so on screen. The interpolation is a convenience for reading the curve's shape; it is not a published rate, and the real decline is not linear.
Miscarriage. The Danish national register linkage study Maternal age and fetal loss: population based register linkage study covered every reproductive outcome in Denmark from 1978 to 1992 — 634,272 women and 1,221,546 pregnancy outcomes. Because only hospital-admitted miscarriages were captured, the authors published a corrected series on the assumption that 80 percent of recognised miscarriages led to admission: 13.3 percent at ages 12 to 19, 11.1 percent at 20 to 24, 11.9 percent at 25 to 29, 15.0 percent at 30 to 34, 24.6 percent at 35 to 39, 51.0 percent at 40 to 44 and 93.4 percent at 45 or more. Those are the figures this page reports.
Miscarriage history strata. The same study reported that among women aged 25 to 29 with no history of miscarriage, spontaneous abortion occurred in 8.9 percent of pregnancies in nulliparous women and 9.3 percent in parous women; with a history of one, 12.4 and 11.8 percent; with a history of two, 22.7 and 17.7 percent. The tool shows those sub-figures when you select a stratum, and it labels them as applying to that age band only, because that is the only band the paper broke out this way.
Down syndrome. ACOG's FAQ lists the risk of a pregnancy affected by Down syndrome as 1 in 1,250 at age 20, 1 in 1,000 at age 25, 1 in 714 at age 30, 1 in 294 at age 35 and 1 in 86 at age 40. The tool reports the nearest listed age rather than interpolating, because ACOG publishes five points and not a curve.
Why a Population Rate Is Not a Prediction
This section exists because it is the single most misused idea in fertility reporting, and putting it in a footnote would be dishonest. When a study says 15 percent of pregnancies at ages 30 to 34 ended in miscarriage, it is describing a count in a register. It is not saying that a given pregnancy at 32 carries a 15 percent risk in any personally meaningful sense, because the register population is heterogeneous: it contains people with known conditions and people without, people on their first pregnancy and their fifth, people with very different underlying probabilities all averaged into one figure.
The same heterogeneity distorts the conception figures in a specific and well-recognised way. If everyone had the same 25 percent per-cycle chance, then after twelve cycles almost everyone would have conceived. Real cohorts do not behave like that, because the people with the highest per-cycle probability conceive first and leave the pool, so the observed rate among those still trying falls month by month even though nobody's individual probability changed. That is why the cumulative number this page computes is an upper-bound sketch rather than an observed statistic, and why it carries a label saying so.
The practical upshot is blunt. If you are trying to conceive, the number that matters is not on this page and cannot be, because generating it requires history, examination and testing. The NICHD summary of possible causes of female infertility gives a sense of how many distinct mechanisms sit behind an individual result, none of which a web page can see.
What the Sources Do Not Cover
Male age is absent from both sources as a rate. ACOG notes that male fertility also declines with age but not as predictably, and gives no figure. This page therefore has no male-age input, which is a real gap rather than an oversight, and it would be worse to invent a number to fill it.
Era and setting matter too. The Danish register ran from 1978 to 1992. Recognition of early pregnancy has changed since then, home testing is far more sensitive, and the pattern of who is pregnant at what age has shifted substantially in every high-income country. The paper itself notes that the overall recorded miscarriage rate rose across its own study periods for reasons of ascertainment rather than biology.
Conditions that dominate individual outcomes are invisible here. Endometriosis, uterine fibroids, thyroid disease, polycystic ovary syndrome, tubal factors, previous surgery and a long list of others all shift both conception and miscarriage probability, and none of them are inputs. Assisted reproduction changes the picture again, and none of these figures describe treated cycles.
How the Cumulative Figure Is Calculated
The model is the simplest one available: if each cycle carries an independent probability p of conception, the probability of not conceiving in n cycles is one minus p, raised to the power n, and the cumulative probability is one minus that. At the default age of 32, the per-cycle rate is the ACOG 25 percent anchor, so twelve cycles gives 1 − 0.75 to the twelfth power, which is 0.968, or about 96.8 percent.
That figure is obviously too high to describe any real cohort, and its being obviously too high is the useful part. It is what a constant-rate model predicts, and the gap between it and reality is the size of the heterogeneity effect described above. The page shows it because seeing where a naive model breaks is more instructive than not seeing the model at all — but it is a demonstration, not a statistic, and the tool says so on screen.
Arb Digital builds calculators and content that name their sources and state their limits plainly — the same standard as this page.
Browse All Free Tools Talk To Our TeamCommon Mistakes to Avoid
- Reading a population rate as a personal probability — it is an average over an extremely varied group, and it describes none of them individually.
- Treating the interpolated ages as published figures — ACOG gives two anchors, and everything between them on this page is a straight line drawn for readability.
- Taking the cumulative number at face value — a constant-rate model overstates cumulative conception in every real cohort, because the most fertile people leave the pool first.
- Applying 1978 to 1992 Danish register rates as current local rates — ascertainment, testing and the age distribution of pregnancy have all changed since.
- Using any of this to decide anything — timing, treatment and testing decisions belong with a fertility specialist who can actually examine and test you.
Related Free Tools From Arb Digital
Find the fertile window of a single cycle with the ovulation calculator or the fertility calculator, look at cycle-phase timing with the luteal phase calculator and the implantation date calculator, work out an estimated delivery date with the due date calculator, or convert a date into a gestational week with the pregnancy week calculator. The full free online tools hub lists every health tool we publish.
Frequently Asked Questions
No. It reports rates observed across large populations. Individual fertility varies enormously at every age and depends on factors no web page can see, so a population rate is not a personal probability and cannot be converted into one.
From ACOG's patient FAQ on having a baby after age 35, which states that around 1 in 4 healthy couples in their 20s and early 30s conceive in any single cycle, and around 1 in 10 by age 40. Those are the only two anchor figures the source publishes.
Because ACOG publishes two per-cycle figures rather than a curve. Between age 32 and age 40 this page draws a straight line between them so the shape is readable, and it labels those values as interpolated rather than published.
A Danish national register linkage study covering every reproductive outcome in Denmark from 1978 to 1992, comprising 634,272 women and 1,221,546 pregnancy outcomes. The page reports the authors' corrected series, which assumes 80 percent of recognised miscarriages led to hospital admission.
Because a constant-rate geometric model assumes everyone shares the same per-cycle probability. In real cohorts the people with the highest probability conceive first and leave the pool, so observed cumulative rates are lower. The figure is a demonstration of the model, not an observed statistic.
Because neither source publishes male fertility as a rate. ACOG notes that male fertility declines with age but less predictably, and gives no figure. Inventing one to fill the gap would be worse than leaving it visible.
No. Both sources describe natural conception and pregnancies in the general population. Treated cycles are reported separately in the clinical literature and are outside the scope of this page.
No. This page reports published population statistics and offers no view on timing, testing, egg freezing or treatment. Those decisions belong with a fertility specialist or an obstetric provider who knows your history.
This page reproduces published population statistics for general information only. It is not medical advice, it makes no prediction about any individual, it recommends no course of action, and it is not a substitute for care from a qualified fertility specialist or obstetric provider.
