Fertility Calculator Suite
Clinical-grade tools used by IVF clinics — free to use, free to join. Create a free account to see your results.
Ovulation & Fertile Window Calculator
Find your most fertile days. Uses the luteal phase model validated by Wilcox et al. (NEJM, 2000).
Your Results
Day-by-day conception probability
3-month fertility calendar
Timing recommendations
Next 3 cycles
Due Date Calculator
Calculate your estimated due date (EDD) using Naegele's Rule, with your full NHS antenatal schedule and week-by-week milestones.
Your Results
NHS Antenatal Appointment Schedule
Based on current NICE guidelines. Dates shown are targets.
Week-by-week milestones
HCG Doubling Time Calculator
Analyse how quickly your beta-HCG is rising. Healthy early pregnancies typically double every 48–72 hours when HCG is below 1,200 mIU/mL.
Your Results
Semen Analysis Interpreter
Enter values from your semen analysis report. Each parameter is assessed against WHO 2021 (6th edition) lower reference limits.
FSH and LH are blood tests sometimes ordered alongside a semen analysis to check whether low sperm count has a hormonal cause. Enter values from your lab report if you have them.
Your Results WHO 2021
Related Reading
If you're under 35 and have been trying for 12 months, or over 35 and trying for 6 months, ask for an NHS fertility referral. Testing is free on the NHS.
For the most accurate ovulation prediction, track 3–6 cycles. Ovulation predictor kits (OPKs) detect the LH surge 24–48 hours before ovulation.
HCG levels vary widely between individuals. A single value matters less than the rate of rise. Always discuss results with your healthcare provider.