Ovulation & Fertile Window Calculator
Calculator ToolsOvulation day, fertile days and next period
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History
All history →Ovulation & Fertile Window Calculator — at a glance
Plan better by finding the days you are most likely to be fertile.
Last period 1 Oct
28-day cycle
Calculate Ovulation
Ovulation 15 Oct
Fertile 10–16 Oct
How to use it — step by step
The first day of your last period, your usual cycle length and luteal phase.
1
Enter your numbers
Fill in the fields — sensible example values are already filled in.
2
Pick your options
Choose any dropdowns or switches that apply to your case.
3
Calculate Ovulation
Press the button. The result is created instantly on your device.
4
Read the answer
The main answer is shown big at the top, with details below it.
Pro tips
Small things that make the result better.
✦Cycle length is counted from day 1 of one period to day 1 of the next.
✦Irregular cycles make estimates less reliable.
✦Talk to a doctor for medical advice about fertility.
Quick facts
Freeno signup, no limit
Instantresult in a moment
Privatenothing is uploaded
Any devicephone, tablet or PC
Frequently Asked Questions
How is ovulation estimated?+
Ovulation usually happens about 14 days before the next period starts.
Is this a contraception tool?+
No. Do not rely on it to avoid pregnancy.
Is my data safe?+
Yes. Everything runs inside your own browser. Your text, files and images are never uploaded to any server.
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