Estimate an expected delivery date, pregnancy week and trimester from your last period, conception, IVF transfer, ultrasound dating or an existing due date.
All calculations use whole calendar days and run locally in your browser.
Calendar dates for each completed gestational week, based on the current result.
| Gestational milestone | Calendar date | Trimester guide | Status on as-of date | Reference note |
|---|---|---|---|---|
| Calculate a due date to generate the week calendar. | ||||
The standard menstrual method counts 280 days from the first day of the last menstrual period. A cycle-length adjustment moves the estimated ovulation and delivery dates when the average cycle is shorter or longer than 28 days.
A known conception date uses 266 days. IVF uses embryo age and transfer date. Ultrasound mode projects 40 weeks from the gestational age documented on the selected scan date.
| Method | Calculation | Important limitation |
|---|---|---|
| LMP | First day of LMP + 280 days + cycle adjustment | Depends on reliable menstrual dates and cycle assumptions. |
| Conception | Conception or ovulation date + 266 days | Ovulation and fertilisation may not occur on the assumed day. |
| Day-5 IVF transfer | Transfer date + 261 days | Use the embryo age and transfer date recorded by the clinic. |
| Day-3 IVF transfer | Transfer date + 263 days | Use ART-derived dating for an IVF pregnancy. |
| Ultrasound | Scan date + 280 days − gestational age on scan | This calculator does not apply clinical redating thresholds. |
Select last menstrual period, conception date, IVF transfer, ultrasound dating or an existing due date.
Provide the requested date and any method-specific details such as cycle length, embryo age or scan gestational age.
Use today or select another date to calculate gestational age and pregnancy progress for that day.
View the estimated due date, current pregnancy week, trimester, conception estimate and typical 37-to-42-week delivery window.
Explore the week-by-week date table, then copy, print or download the result and CSV calendar.
Pregnancy is conventionally dated as 40 weeks from the first day of the last menstrual period, but normal delivery can occur across a broader range. Menstrual recall, irregular cycles and ovulation timing can all change an LMP estimate.
First-trimester ultrasound is generally the most accurate ultrasound period for confirming gestational age. The official date used for care should be established and documented by the maternity team.
This page uses a simple public-information trimester guide: weeks 1–12, weeks 13–28 and week 29 onward. The table includes dates at 37, 39, 40 and 42 weeks, but it does not schedule tests, appointments, induction or delivery.
The entered dates are processed in the browser. No page-specific upload, account, database or external date service is used. Reset clears the active result.
Check the selected method, exact source date, cycle length, embryo age, ultrasound weeks and days, and as-of date. When medical records disagree, ask the maternity team which date is official.
Professional guidance on 280-day LMP dating, first-trimester ultrasound and ART-derived dates. Read the guidance.
Public guidance on cycle adjustment, the 37-to-42-week range and dating scans. Read the guidance.
It estimates the due date, gestational age, current pregnancy week, trimester, estimated conception date, estimated last menstrual period and a week-by-week calendar.
The calculator supports the first day of the last menstrual period, a known conception or ovulation date, day-3 or day-5 IVF embryo transfer, an ultrasound date with measured gestational age, and an existing estimated due date.
The standard estimate adds 280 days to the first day of the last menstrual period. When a cycle length other than 28 days is entered, the result is adjusted by the difference.
Obstetric gestational age is conventionally counted from the first day of the last menstrual period, approximately two weeks before conception in a typical 28-day cycle.
Yes. Enter a cycle length from 21 to 45 days. The calculator shifts the estimated ovulation and due date relative to the standard 28-day cycle.
The calculator adds 266 days, or 38 weeks, to the entered conception or ovulation date and estimates the corresponding menstrual start date 14 days earlier.
For a day-5 embryo transfer, the calculator adds 261 days to the transfer date. For a day-3 embryo transfer, it adds 263 days.
Yes. Enter the scan date and the gestational age shown on the report in completed weeks and additional days. The calculator projects the date at 40 weeks.
No. It performs date arithmetic only. Clinical redating decisions depend on ultrasound timing, measurement quality, prior dating information and professional judgment.
Professional guidance describes first-trimester ultrasound as the most accurate method for establishing or confirming gestational age. Your clinician should determine the official due date.
Gestational age is the number of completed weeks and days counted from the estimated start of the last menstrual period, not from conception.
Gestational age is usually about two weeks greater than age counted from conception. This page reports obstetric gestational age because that is the standard used for pregnancy dating.
It means 12 full weeks have been completed and the pregnancy is three days into the next week.
This calculator uses a simple educational guide: weeks 1–12 are the first trimester, weeks 13–28 the second, and week 29 onward the third. Clinical conventions can vary slightly.
The page shows 37 weeks 0 days through 42 weeks 0 days from the estimated menstrual start, matching the broad range commonly used in public pregnancy guidance.
No. An estimated due date is a reference point, not a prediction of the exact day labor or birth will occur.
Yes. Choose Existing due date to calculate the estimated menstrual start, conception date, gestational age and week calendar from that date.
Yes. Change the as-of date to any date in the supported range to view the estimated gestational age and timeline on that day.
The calculator shows how many days have passed since the estimated due date and continues the gestational-week count for historical reference.
The result is labelled as before the estimated pregnancy start rather than showing a negative pregnancy week.
All calculations use whole calendar days in UTC, preventing daylight-saving changes from adding or removing a day. Leap dates are handled by the calendar automatically.
Entered dates are accepted from January 1, 1900 through December 31, 2100. Derived timeline dates may extend slightly beyond the entered year.
No. It cannot detect pregnancy, confirm viability or diagnose a medical condition. A pregnancy test and qualified healthcare professional are needed for medical confirmation.
No. The date calculation does not identify the number of fetuses. Ultrasound and clinical care are required for that information.
No. It provides an educational date estimate only and does not replace prenatal care, ultrasound dating, diagnosis or treatment.
No. Follow the dates and instructions provided by your maternity team. Use this page only as a planning and calculation aid.
Yes. The result can be downloaded as a text report and the week-by-week dates can be downloaded as CSV. Filenames begin with correctioncopy.com_.
Yes. Use Print to open the browser print dialog, where you can print the result or save it as a PDF when the browser supports that option.
No page-specific request sends the entered dates to a server. Calculations and exports are generated in the browser, and Reset clears the current workspace.
No account or installation is required. JavaScript must be enabled for calculations, copying and downloads.
Yes. The form and result stack on smaller screens, controls are touch-friendly and the date table can be scrolled horizontally when necessary.
Do not choose between them using this page alone. Ask your obstetrician, midwife or other qualified clinician to establish the official estimated due date.
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