Start with your last period
Use the first day of bleeding from your most recent menstrual period.
Fertility calculator
OvulationCalculator
Estimate your ovulation date, fertile window, and likely next period using your last period date and average cycle length.
This calculator supports cycle lengths from 22 to 44 days, period lengths from 3 to 10 days, and estimates a six-day fertile window. It works best for regular cycles. Estimates are informational only and are not a diagnosis, contraception method, or substitute for medical advice.
Calculate your fertile window
Use the first day of bleeding from your most recent period.
Enter the first day of your last period to see your ovulation estimate.
Trying to conceive for 12 months, or 6 months if you are 35 or older? A fertility consultation can help you understand the next step.
Guide
How to use this fertile window calculator
Choose your period length
Select how many days your bleeding usually lasts, then choose your average cycle length.
Review the fertile window
The fertile window includes the five days before ovulation and the day of ovulation.
What it estimates
Likely fertile days, estimated ovulation, and predicted next period dates.
What can shift results
Stress, illness, PCOS, breastfeeding, age, and irregular cycles can change ovulation timing.
When to get help
Speak with a specialist after 12 months of trying, or 6 months if you are 35 or older.
Common questions
Ovulation calculator FAQs
How does an ovulation calculator work?
An ovulation calculator estimates ovulation by counting back about 14 days from your expected next period date. The fertile window is usually the five days around ovulation and the ovulation day.
Is the ovulation date exact?
No. Ovulation can vary from cycle to cycle due to stress, illness, irregular periods, PCOS, age, and other health factors. Use the result as an estimate.
When should I see a fertility specialist?
Consider a fertility consultation if you have been trying for 12 months, or 6 months if you are 35 or older. Seek care earlier for irregular cycles, known reproductive conditions, or previous fertility concerns.
Can I use this calculator with irregular periods?
You can use it as a rough guide, but irregular cycles make ovulation harder to predict. Tracking symptoms and consulting a specialist can give a clearer picture.
Next steps
Explore fertility care at Pluro
If you are planning pregnancy, comparing symptoms, or unsure about irregular cycles, explore Pluro centres and fertility resources for personalised care.