Ovulation Calculator
Predict your fertile window, ovulation date, and next period based on your cycle length.
How to Use the Ovulation Calculator
- Select Standard Cycle for regular cycles or Irregular Cycle for varying cycle lengths.
- Enter the first day of your last menstrual period.
- Enter your average cycle length (21-35 days). For irregular cycles, enter shortest and longest.
- Click Calculate to see your fertile window, ovulation day, and next period date.
Formula & Method
Ovulation Day (Standard):Ovulation = LMP Date + (Cycle Length - 14)
Fertile Window:Start = Ovulation Day - 5 daysEnd = Ovulation Day + 1 day
Next Period:Next Period = LMP Date + Cycle Length
Irregular Cycles:
Uses shortest and longest cycle to estimate a range of possible ovulation dates.
Examples
| Cycle Length | LMP Date | Ovulation | Fertile Window | Next Period |
|---|---|---|---|---|
| 28 days | Jan 1 | Jan 15 | Jan 10-16 | Jan 29 |
| 30 days | Jan 1 | Jan 17 | Jan 12-18 | Jan 31 |
| 26 days | Jan 1 | Jan 13 | Jan 8-14 | Jan 27 |
Frequently Asked Questions
How accurate is this ovulation calculator?
This calculator provides estimates based on cycle length. For the most accurate prediction, track basal body temperature, cervical mucus, and use ovulation predictor kits (OPKs). The calculator is about 80% accurate for women with regular cycles.
Can I get pregnant outside my fertile window?
Sperm can survive up to 5 days in the reproductive tract. While pregnancy is most likely during the fertile window, it is possible to conceive from intercourse up to 5 days before ovulation.
My cycles are irregular. Can I still use this?
Yes, use the Irregular Cycle tab. Enter your shortest and longest cycle lengths to get a range of possible ovulation dates. Consider combining with BBT tracking for better accuracy.
People Also Ask
When am I most fertile?
You are most fertile 2 days before ovulation and the day of ovulation. Sperm can survive up to 5 days, so intercourse during the 5 days before ovulation can result in pregnancy.
How many days after my period do I ovulate?
For a 28-day cycle, ovulation typically occurs around day 14. For a 30-day cycle, around day 16. Subtract 14 from your cycle length to estimate.
Can I ovulate twice in one cycle?
Yes, it is possible to ovulate twice in one cycle (hyperovulation), which is how fraternal twins occur. However, both ovulations typically happen within 24 hours of each other.