Basal Body Temperature
Your resting body temperature often dips slightly just before ovulation, then raises about half a degree to one degree immediately after. Tracking this daily is one of the most reliable signs that ovulation has occurred.
Accurate Ovulation Calculator & Period Tracker
Based on WHO Standard Days Method® Protocols
A clinical-grade fertility algorithm that runs 100% locally on your device. No cloud storage, no sign-ups, no data selling. Your cycle is your private property.
Tracker Configuration
28 days
Short (22)Avg (28)Long (45)
Privacy First. Your cycle data is processed locally on your device and is never collected by our servers.
Ready to Visualize
Provide your last period start date and click CALCULATE to view your personalized timeline.
How to Use This Tracker
4 simple steps to validate your fertility window.
01
Enter Your Cycle Details
Enter the first day of your last period and your usual cycle length above. If you're not sure, the default 28 days is a good starting point.
02
Review Your Timeline
The calculator instantly maps your specific fertile window and estimating your exact ovulation day based on clinical standards.
03
Double-check Body Signs
Cross-reference these dates with what your body is telling you—like changes in temperature or fluid (see below) for the best accuracy.
04
Plan Your Timing
For conception, aim to have intercourse every other day during your highlighted high-fertility window.
How Our Ovulation Calculator Works
Evidence-based fertility predictions using the clinical calendar method.
Understanding the Calendar Method
Our ovulation calculator uses the clinical calendar method (also known as the rhythm method) to predict your fertile window. This evidence-based approach combines your unique menstrual cycle history with standardized reproductive biology to identify your most fertile days each month.
The calendar method works by tracking your menstrual cycle length over time and using that data to predict when ovulation will occur. According to the World Health Organization, ovulation typically happens about 14 days before your next period begins, the luteal phase. By tracking your menstrual cycle history, we can work backwards from your cycle length to estimate your ovulation date and the surrounding fertile window.
Your privacy comes first. All calculations happen right here in your browser using secure code. Your personal data never leaves your device and isn't sent to any outside servers. No account needed and no data saved. It's just private tracking.
Our Calculation Methodology
Primary Fertile Indicators
Monitor these secondary biological markers to validate calendar predictions and identify your window in real-time.
Cervical Mucus Changes
As your fertile window opens, you'll notice cervical fluid becoming clear, slippery, and stretchy, like raw egg whites. This key ovulation symptom is nature's way of helping sperm survive and travel.
Cervical Position & Texture
During your most fertile days, the cervix tends to rise higher, feel softer like your lips, and open slightly. After ovulation passes, it drops lower and feels firmer, signaling the end of the fertile window.
Heightened Senses & Libido
Many women notice a sharper sense of smell or a subtle boost in energy and libido when they're most fertile. It's a common biological cue that your body is physically ready for conception.
Mittelschmerz (Ovulation Pain)
About one in five women feel a brief twinge or cramp on one side of the lower abdomen when an egg is released. This localized pain, called Mittelschmerz, implies ovulation is happening right now.
Breast Tenderness
After ovulation, rising progesterone often causes breast sensitivity or fullness. If you feel this symptom, it's a good sign you've successfully entered the luteal phase of your cycle.
LH Surge Detection
Luteinizing hormone (LH) surges 24 to 36 hours before the egg is released. Using Ovulation Predictor Kits (OPKs) to detect this surge gives you a reliable heads up before your peak fertile day.
Energy & Mood Shifts
You might feel more social and confident right before ovulation thanks to peak estrogen. Afterwards, progesterone can bring a calmer, more inward energy as your cycle winds down towards your period.
Frequently Asked Questions
Common questions about ovulation tracking, fertility windows, and menstrual cycle predictions.
How accurate is this ovulation calculator?
It's a reliable baseline based on the clinical calendar method. Since every body is unique and factors like stress or sleep can shift your cycle, it works best when you pair it with tracking your body's natural signs like temperature and cervical mucus.
When does ovulation happen after a period?
It's tied to when your next period starts. Typically, ovulation happens about 14 days before your next flow begins. In a standard 28-day cycle, that's day 14. If your cycle is longer, say 30 days, it's likely around day 16.
When is the absolute best time to conceive?
Your fertile window is the five days leading up to ovulation, plus the day of ovulation itself. The highest chances are often the two days before ovulation. This ensures sperm is already present when the egg is released.
Can I get pregnant while on my period?
It is rare, but possible. Sperm can live inside the body for up to five days. If you have a short cycle and ovulate early, unprotected sex towards the end of your period could lead to conception.
How long does ovulation last?
The egg is only viable for about 12 to 24 hours after it's released. However, because sperm can survive for several days, your actual fertile window lasts about six days in total.
Can I use this tracker for contraception?
No. This tool is designed for pregnancy planning and education only. It calculates averages rather than your real-time biology. If you are actively trying to avoid pregnancy, please rely on professional medical advice or proven contraception methods.
Why does my cycle length change sometimes?
It's completely normal for your cycle to vary slightly. Your follicular phase, the time before ovulation, moves based on stress, diet, or illness. The time after ovulation, known as the luteal phase, is usually a very consistent 14 days.
What are the real odds of getting pregnant each month?
For healthy couples timing it right, there's about a 20 to 30 percent chance of conceiving each cycle. It often takes a few months even when everything is perfect, so be patient with yourself as it's normal for it not to happen immediately.
Can stress delay my ovulation?
Yes. Physical or emotional stress triggers cortisol, which can signal your brain to pause reproductive hormones temporarily. It's a survival mechanism where your body waits for a calmer time to safely start a pregnancy.
Should I track symptoms like mucus or temperature?
Absolutely. A calendar gives you the estimated dates, but physical signs like egg-white cervical mucus give you the real-time proof. Combining these math-based predictions with your body's actual signals is the most accurate way to track.
What is the Luteal Phase and why does it matter?
It's the phase between ovulation and your next period. Your body produces progesterone here to prepare for a possible pregnancy. If you don't conceive, this phase ends when your period starts.
Is this calculator accurate for irregular periods?
If your cycle varies by more than a week month to month, calendar-based predictions will be less precise. In that case, we recommend focusing more on tracking real-time signs like cervical fluids or using Ovulation Predictor Kits (OPKs) alongside this tool.