Trying to Conceive: Fertility & Ovulation Calculators
Find your likely ovulation day, your fertile window and your chances of conceiving each cycle.
Know Your Cycle. Plan Your Pregnancy.
Free Fertility, Ovulation& Pregnancy Calculators
Estimate your ovulation day, fertile window, due date or IVF/FET due date in seconds. PanaKit's 25 calculators use standard clinical dating rules, run in your browser and need no sign-up. Results are educational estimates, not medical advice.
25 free calculators4 categoriesNo sign-up
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Most Popular Fertility & Pregnancy Calculators
Estimate your ovulation day, fertile window, due date or IVF/FET due date in seconds with standard clinical dating rules.
- FertilityOvulation Calculator
Estimate your ovulation day from your last period and cycle length.
- FertilityFertile Window Calculator
See the 6 days each cycle when conception is possible.
- PregnancyPregnancy Due Date Calculator
Your due date from your last period, conception date or IVF transfer.
- PregnancyGestational Age Calculator
How many weeks and days pregnant you are, five ways.
- PregnancyIVF Due Date Calculator
IVF and FET due dates for Day 3 or Day 5 transfers.
- FertilityImplantation Calculator
When implantation may happen, and when to test.
Every Stage Covered
Calculators by Stage
Whatever stage you're in, pick a category and open the tool you need.
Pregnant: Due Date & Pregnancy Calculators
Estimate your due date from your last period, conception, an ultrasound or an IVF/FET transfer, and track gestational age and weight gain.
Tracking Your Cycle: Period & Menstrual Health Calculators
Predict your next period, see which cycle phase you are in, and understand your flow.
Women's Health Calculators
Body composition, nutrition and sizing tools built around women's reference ranges.
How PanaKit Calculates Your Dates
Due date (Naegele's rule): first day of your last menstrual period (LMP) + 280 days (40 weeks), assuming a 28-day cycle. Our due date calculator can adjust for longer or shorter cycles.¹ ²
Ovulation day: LMP + (cycle length − 14) days, because the luteal phase averages about 14 days.³
Fertile window: the 5 days before ovulation plus ovulation day itself.⁴
IVF / FET due date: transfer date + 261 days for a Day 5 transfer, or + 263 days for a Day 3 transfer. Fresh and frozen transfers use the same math.¹
Ultrasound dating: ACOG says an early (first-trimester) ultrasound is the most accurate way to establish or confirm gestational age.¹
These are estimates. Your clinician's dating always takes priority. See how PanaKit works →
Sources:
¹ ACOG Committee Opinion No. 700, Methods for Estimating the Due Date (2017): acog.org
² NHS, Pregnancy due date calculator: nhs.uk
³ ACOG, Trying to Get Pregnant? Here's When to Have Sex: ovulation typically happens about 14 days before your period starts. acog.org
⁴ Wilcox AJ, Weinberg CR, Baird DD. Timing of sexual intercourse in relation to ovulation. N Engl J Med 1995;333:1517–21.
Popular Fertility & Pregnancy Guides
Plain-English guides that explain dating scans, ovulation timing and early pregnancy questions.
How to Calculate Your FET Due Date (Day 3 vs Day 5)
Learn how frozen embryo transfer (FET) due dates are calculated from transfer date and embryo age, Day 5 adds 261 days, Day 3 adds 263, and why this differs from LMP dating. Use PanaKit's free IVF/FET calculator.
Read guide →
Gestational Age vs Fetal Age: Why Your Weeks, Scan, and Due Date Don’t Match
Gestational age starts from your last period; fetal age from conception, about two weeks less. See why dating scans change due dates, and what 8+4 means.
Read guide →
When Do You Ovulate? Ovulation Day by Cycle Length
Find your estimated ovulation day based on your exact cycle length, from 21 to 35 days. See the full day-by-day breakdown and calculate your own dates.
Read guide →
Implantation Bleeding: What It Looks Like, and When to Test
Spotting and wondering if it's implantation bleeding? Here's how to tell it apart from a period, and why testing too soon can give you a false negative.
Read guide →
Can You Ovulate While Breastfeeding? What to Watch For
Yes, ovulation can return while breastfeeding, often before your period does. Here's the real timeline, why breastfeeding delays it, and the signs to watch for.
Read guide →
How Many Weeks Pregnant Am I? Simple Calculation
Work out how many weeks pregnant you are from your last period or due date, and understand why your own count and your doctor's sometimes don't quite match.
Read guide →Frequently Asked Questions
Yes. Every PanaKit calculator is free to use, with no account or sign-up.
It gives an estimate. Using Naegele's rule, the due date is 280 days (40 weeks) after the first day of your last period, assuming a 28-day cycle. ACOG notes that an early ultrasound is the most accurate way to confirm or adjust gestational age. Few babies arrive exactly on their due date, so treat it as a target, not a deadline.
PanaKit adds your cycle length minus 14 days to the first day of your last period, because the luteal phase lasts about 14 days. The fertile window is the 5 days before ovulation plus ovulation day itself. Cycles vary, so ovulation tests or temperature tracking can help confirm it.
From the transfer date: add 261 days for a Day 5 (blastocyst) transfer, or 263 days for a Day 3 transfer. Fresh and frozen transfers use the same math. Your clinic's date takes priority.
No. Calculations run in your browser, and your inputs are not sent to or stored on our servers. We use Google Analytics to understand overall site usage, such as page visits. See our Privacy Policy for details.
No. PanaKit results are educational estimates, not a diagnosis or treatment plan. Always follow the advice of your doctor, midwife or fertility clinic.
Privacy & trust
Private by design: your calculator inputs stay in your browser and are not stored on our servers. We use Google Analytics to measure site visits. Privacy Policy
Standard clinical methods: Naegele's rule, luteal-phase ovulation timing and IVF transfer dating, with sources listed above.
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Stop Guessing Your Dates
One place for ovulation, fertility, pregnancy and cycle calculators. Free, private and no sign-up.
PanaKit calculators and guides are for general education only. They are not medical advice, diagnosis or treatment. Results are estimates based on typical cycles and standard dating rules, and your body may differ. Always talk to your doctor, midwife or fertility clinic about your health, and seek urgent care for severe pain, heavy bleeding or other worrying symptoms.