Female fertility declines gradually from the late 20s and more steeply after 35, mainly because the number and quality of eggs fall. Most couples under 35 conceive within a year of regular unprotected sex; specialists recommend seeing a doctor after 12 months of trying (6 months over 35).
How to use the Fertility by Age Calculator
- Age
- Months of trying
Results update as you type, and every field accepts the units shown in its menu.
How it works
Choose your age and how many months you plan to try. The figures assume regular unprotected sex in healthy couples; individual fertility varies a lot.
Inputs explained
| Field | What to enter |
|---|---|
| Age | In years |
| Months of trying | A number |
What each result means
- Chance within your chosen months = (1 – (1 – [Chance of conceiving each cycle]÷100)^[Months of trying])×100
- Chance within one year = (1 – (1 – [Chance of conceiving each cycle]÷100)^12)×100
Example values
How the main result changes when Age changes and everything else stays at the example values above:
| Age (years) | Chance of conceiving each cycle (%) |
|---|---|
| 24 | 25 |
| 32 | 15 |
| 40 | 5 |
| 48 | 1 |
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
Chance per cycle: 25% (19–25), 20% (26–29), 15% (30–34), 10% (35–39), 5% (40–44), 1% (45–49)
Chance within n cycles = 1 − (1 − p)ⁿ
Worked example
Inputs — Age: 32 years; Months of trying: 12.
Results — Chance of conceiving each cycle = 15 %; Chance within your chosen months = 86 %; Chance within one year = 86 %; When to seek advice = After 12 months of trying.
Key terms
- Fecundability
- The probability of conceiving in one menstrual cycle.
Frequently asked questions
At what age does fertility decline?
Gradually from about 30, and faster after 35.
Does male age matter?
Yes, sperm quality declines too, especially after about 40–45.
Can I preserve fertility?
Egg freezing before 35 gives the best chance; it is not a guarantee.