Ovulation Calculator
Ovulation Calculator
How It Works
- Ovulation Estimate: Ovulation ≈ LMP + (cycle length − luteal phase). Default luteal phase is 14 days.
- Fertile Window: Typically 5 days before ovulation to 1 day after (sperm can survive up to 5 days).
- Next Period: Estimated as LMP + cycle length.
- Projections: Future cycles calculated by advancing LMP by cycle length for each projection.
Overview
Use ToolYard's Ovulation Calculator to estimate your likely ovulation day and fertile window based on your last menstrual period (LMP) and average cycle length. The tool uses the commonly accepted method (ovulation ≈ cycle length − luteal length) with a default luteal phase of 14 days and produces a five-to-seven day fertile window (five days before ovulation to one day after). Enter your LMP and cycle length to get instant dates, a calendar view of fertile days, and downloadable summaries. All calculations happen locally in your browser — no sign-in or data upload required. Perfect for planning, family planning conversations, or tracking fertility awareness.
About
About Ovulation Calculator
Estimate your ovulation date and fertile window using LMP and cycle length.
Features:
- LMP-based ovulation estimation
- Customizable cycle length (20–40 days)
- Adjustable luteal phase length
- Fertile window calculation
- Multi-cycle projections (1–6 cycles)
- Calendar visualization
- Next period estimation
- Export to CSV
- Print summary
- 100% private - no data stored
FAQ
How accurate is an ovulation calculator?
It provides an estimate based on average cycle patterns. Ovulation varies; ovulation tests (LH surge), ultrasound, or fertility monitoring are more precise.
What is the luteal phase?
The luteal phase is the time from ovulation to the next period — typically ~14 days. It's more consistent than the follicular phase.
Why 5 days before ovulation?
Sperm can survive up to 5 days in the reproductive tract. The fertile window covers the days when conception is most likely.
What if my cycles are irregular?
This calculator assumes regular cycles. For irregular cycles, use an advanced fertility tracking app or consult your healthcare provider.
Can I use this for contraception?
This is an informational tool. For contraception, consult your healthcare provider about evidence-based methods.
Is my data stored?
No. All calculations happen in your browser and are not saved or transmitted.