Ovulation Calculator
Fertile window and ovulation day from your cycle.
Enter your values
Enter the cycle length in days.
Enter the luteal phase length in days.
Enter the current day of cycle you are working with.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Ovulation day of cycle
- Day 14
- Fertile window
- Day 9 to day 14
- Today's status
- Lower chance
- Days until ovulation
- 6 days
Quick answer
Ovulation happens about 14 days before the next period, and the fertile window is the five days before ovulation plus the day itself.
At a glance
| What it does | Fertile window and ovulation day from your cycle. |
|---|---|
| Category | Health |
| Inputs needed | Cycle length, Luteal phase length, Current day of cycle |
| Main output | Ovulation day of cycle |
| Cost | Free — no sign-up, no download |
How to use the Ovulation Calculator
- 1Enter your typical cycle length.
- 2Enter your luteal phase (usually 12–16 days).
- 3Enter today's cycle day to see your status.
Inputs explained
- Cycle length(days)
- Enter the cycle length in days.
- Luteal phase length(days)
- Enter the luteal phase length in days.
- Current day of cycle
- Enter the current day of cycle you are working with.
Worked example
Using the values the calculator loads with:
Inputs
- Cycle length28 days
- Luteal phase length14 days
- Current day of cycle8
Results
- Ovulation day of cycleDay 14
- Fertile windowDay 9 to day 14
- Today's statusLower chance
- Days until ovulation6 days
Frequently asked questions
How long does the egg survive?
About 12–24 hours, but sperm can live up to five days, which is why the fertile window starts before ovulation.
Are these predictions reliable?
They are estimates. Ovulation predictor kits and basal body temperature tracking confirm the actual day.
What do I need to enter into the Ovulation Calculator?
Just 3 values: cycle length, luteal phase length, current day of cycle. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Ovulation Calculator work out the answer?
Ovulation happens about 14 days before the next period, and the fertile window is the five days before ovulation plus the day itself. The working is shown step by step so you can verify the result by hand.
Is the Ovulation Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.