Conception Probability Calculator

Estimate your chance of conception based on your cycle and timing.

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Medical Disclaimer: This tool is for educational and informational purposes only. It does not provide medical advice, diagnosis, or treatment. Results are estimates only. Always consult a qualified healthcare professional for medical decisions. In an emergency, call 995 (Singapore) immediately.

Conception Timeline: Cumulative Success Rates

For a healthy couple aged 25-30 trying naturally, with well-timed intercourse.

1 month ~20%

3 months ~50%

6 months ~72%

12 months ~85%

24 months ~92%

If you are over 35, ACOG recommends seeing a fertility specialist after 6 months of trying. Under 35, seek evaluation after 12 months.

What Affects Your Chances of Conceiving?

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Age

Fertility peaks in your mid-20s and begins declining gradually after 32, more steeply after 37. Women are born with a fixed number of eggs. Men's sperm quality also declines, though more slowly.

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Cycle Regularity

A regular 21-35 day cycle makes predicting ovulation easier. Irregular cycles, common with PCOS or thyroid issues, make timing harder and can signal irregular ovulation.

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Timing of Intercourse

The fertile window is the 5 days before ovulation plus the day of ovulation itself. Having sex every 1-2 days throughout this window maximises the chance of sperm meeting the egg.

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Lifestyle Factors

Maintaining a healthy BMI (18.5-24.9), quitting smoking, reducing alcohol, and managing stress all support fertility. In Singapore, the HPB recommends folic acid 400mcg daily before conception.

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Underlying Health

Conditions like PCOS, endometriosis, blocked tubes, low sperm count, or hormonal imbalances reduce conception probability. KKH and NUH offer fertility workups if needed.

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Duration of Trying

The longer you try without success, the lower the remaining monthly probability. If you have been trying for 12 months (under 35) or 6 months (over 35), a fertility evaluation is the next step.

Monthly Conception Probability by Age

Approximate chance per cycle for a woman with no known fertility issues, trying at the right time.

Age Group	Monthly Chance	After 12 Months	When to See a Doctor
Under 25	~25-30%	~95%	After 12 months
25-29	~20-25%	~88%	After 12 months
30-34	~15-20%	~75%	After 12 months
35-37	~10-15%	~66%	After 6 months
38-40	~8-10%	~52%	After 3-6 months
41-42	~5-7%	~36%	Immediately
43+	~2-5%	~25%	Immediately

How to Improve Your Chances

✓ Track ovulation with OPK strips or a BBT thermometer to pinpoint your fertile window

✓ Have sex every 1-2 days during your fertile window (5 days before + day of ovulation)

✓ Take 400mcg folic acid daily - Start at least 1 month before trying

✓ Achieve or maintain a healthy BMI (18.5-24.9) as both extremes affect ovulation

✓ Quit smoking and reduce alcohol - both significantly impair egg and sperm quality

✓ Ask your partner to wear loose underwear and avoid hot tubs (heat reduces sperm count)

✓ Manage stress with exercise, sleep, or counselling - chronic stress disrupts ovulation

✓ Get a pre-conception check at your GP or KKH Women's Clinic to rule out any issues early

Full TTC guide for Singapore parents →

Frequently Asked Questions

For couples under 35 with no fertility issues, 50% conceive within 3 months and 85% within 12 months. The remaining 15% are diagnosed with infertility after 12 months of trying. Every cycle is independent, so previous attempts don't reduce your current-cycle probability.

Yes, significantly. The egg survives only 12-24 hours after ovulation. Sperm can survive up to 5 days in the reproductive tract. Having sex in the 1-2 days before ovulation is most effective. Random timing throughout the month is much less efficient than timed intercourse.

Yes. PCOS is one of the most common causes of irregular or absent ovulation, which directly reduces monthly conception probability. Many women with PCOS conceive naturally or with minimal intervention (such as Letrozole or Clomid). Speak to a doctor at KKH or NUH for a personalised plan.

Yes. After ovulation, it takes approximately 6-12 days for a fertilised egg to implant, and hCG (the pregnancy hormone) rises enough to be detected by a blood test after 14 days. Home urine tests can sometimes detect pregnancy 10-12 days after ovulation.

MOH guidelines align with international standards: see a doctor after 12 months if under 35, or 6 months if 35 or over. KKH and NUH offer fertility assessment services. Medisave can be used for approved assisted reproduction treatments including IUI and IVF.

Substantially. Studies show smoking reduces female fertility by 40% and male fertility by 20%. Obesity and underweight both disrupt ovulation. Alcohol above 2 units per day reduces conception rates. These are controllable factors that can meaningfully shift your monthly probability.