Pregnancy & Cycle
Due date, conception, ovulation, and pregnancy weight gain calculators — timeline tools for fertility and pregnancy.
Eight calculators covering the menstrual cycle, conception, pregnancy dating and healthy gain. They connect: the cycle tools predict your fertile window, conception works backwards from a due date, and the due date drives everything after it.
All of them are estimates around an average, and pregnancy is unusually variable. Even measured from implantation, normal pregnancies span about five weeks in length — which is why every output here is better read as a range than a date.
Due Date Calculator
Estimate your pregnancy due date from LMP, conception, ultrasound, or IVF transfer.
Open calculatorPregnancy Calculator
Find out how many weeks pregnant you are today, from whichever date you know.
Open calculatorConception Calculator
Estimate the conception date and fertile window from a due date or birth date.
Open calculatorOvulation Calculator
Predict your ovulation date and fertile window for the next three cycles.
Open calculatorPeriod Calculator
Predict your next six periods, fertile windows and ovulation days on a calendar.
Open calculatorMenstrual Cycle Calculator
See which cycle day and phase you are in today, and whether your cycle counts as regular.
Open calculatorPregnancy Weight Gain Calculator
Check whether your pregnancy weight gain is on track with IOM guidelines.
Open calculatorhCG Doubling Time Calculator
Work out the doubling time and 48-hour rise between two quantitative hCG results.
Open calculatorWhich one you need
| Where you are | Use | Gives you |
|---|---|---|
| Tracking your cycle | Period | Six cycles of period dates and fertile windows on a calendar |
| Wondering what phase you are in | Menstrual Cycle | Today's cycle day and phase, plus a regularity assessment |
| Trying to conceive | Ovulation | Your fertile window for the next three cycles |
| Newly pregnant | Due Date | Due date plus a dated 42-week timeline |
| Pregnant and asking how far along | Pregnancy | Gestational age in weeks and days from any date you know |
| Working backwards | Conception | The likely conception window from a due or birth date |
| Pregnant and tracking weight | Pregnancy Weight Gain | Recommended gain from your pre-pregnancy BMI |
| Holding two early blood results | hCG Doubling Time | Doubling time and 48-hour rise, against published ranges |
The counting conventions that confuse everyone
Three quirks account for most of the confusion in this category, and none of them means anything is wrong.
- Week 1 is before you are pregnant
- Pregnancy is counted from the first day of your last period, about two weeks before conception. By the time a test is positive you are called four weeks pregnant. The convention exists because the period date is knowable and the conception date is not.
- The week number is one above your gestational age
- At 8 weeks and 4 days you have completed 8 weeks and are in week 9 — the same way a one-year-old is in their second year. Both figures are correct and both appear on the calculator.
- The fertile window closes at ovulation, not after
- It opens five days before ovulation and shuts within a day of it, because sperm survive up to five days while an egg lasts 12 to 24 hours. By the time most people detect ovulation, the window has passed.
How much to trust the dates
- IVF transfer: accurate to about a day. The only case where conception is known rather than estimated.
- First-trimester ultrasound: ±5–7 days, and the method every guideline prefers. If it disagrees with your period dates by more than a week, the scan is what your care team will use.
- Last menstrual period: ±1–2 weeks with regular cycles, less with irregular ones. Assumes a 28-day cycle and ovulation on day 14.
- Later ultrasound: ±2–3 weeks. Good for assessing growth, poor for dating, which is why due dates are not revised late.
None of this replaces your care team
These calculators inform; they do not monitor. Bleeding, reduced fetal movement, severe headache or contractions before 37 weeks all warrant contacting your midwife or doctor immediately, whatever any page here says about your dates.
Frequently asked questions
Related articles
How Your Due Date Is Calculated (and Why It's an Estimate)
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Read articleOvulation and the Fertile Window: How to Time Conception
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Read articlePregnancy Weight Gain: What's Recommended and Why It's a Range
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Read articleFirst Trimester Timeline: What's Happening Week by Week
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Read articleUnderstanding Your Cycle Length: What's Normal and What's Not
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Read articleDue Date Accuracy by Method: LMP vs. Ultrasound vs. IVF
Four ways to date a pregnancy, accurate to anywhere from one day to two weeks. Which one your date came from tells you how much to trust it — and what happens when two of them disagree.
Read articlePrinted from mystatura.com — for general information only, not medical advice.