Ovulation & Fertility Calculator
Calculate your fertile window, peak ovulation day, and next period based on cycle length.
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Normal range: 21–35 days. Average is 28 days.
Fertile Window
27 Mar 2026 – 2 Apr 2026
6 days — highest chance of conception
Peak Ovulation Day
1 Apr 2026
Day 14 of your cycle
Next Period
15 Apr 2026
Last Safe Day
26 Mar 2026
Next 14 Days
Wed
18
Period
Thu
19
Period
Fri
20
Period
Sat
21
Period
Sun
22
Period
Mon
23
Tue
24
Wed
25
Thu
26
Fri
27
Fertile
Sat
28
Fertile
Sun
29
Fertile
Mon
30
Fertile
Tue
31
Fertile
Disclaimer
This calculator is for informational purposes only. Ovulation timing varies based on cycle irregularity, stress, illness, and other factors. This tool should not be used as a primary method of contraception or for medical decisions. Consult a gynecologist for personalized advice.
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About this tool
How to use Ovulation & Fertility Calculator
- 1Enter the first day of your last menstrual period (LMP)
- 2Set your average cycle length (21–35 days, default 28)
- 3View fertile window, peak ovulation day, and next expected period
- 4Check the 14-day calendar for day-by-day colour coding
Frequently Asked Questions
How is the ovulation date calculated?
Ovulation typically occurs 14 days before the next period, regardless of cycle length. For a 28-day cycle, ovulation is on day 14. For a 32-day cycle, ovulation is on day 18. This is based on the standard luteal phase of 14 days.
What is the fertile window?
The fertile window is the 6-day period ending on the day of ovulation — 5 days before ovulation plus the ovulation day itself. Sperm can survive up to 5 days, so intercourse in this window can result in fertilization.
How accurate is this calculator?
This calculator is as accurate as any standard period tracking app. However, actual ovulation can vary due to stress, illness, travel, or irregular cycles. It is for informational purposes only and should not be used as a primary method of contraception.
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