Calcaxis

Due Date Calculator

Estimate due date, current pregnancy week, trimester, and milestone dates from LMP, conception date, or IVF transfer date.

Pregnancy dating is usually discussed from the last menstrual period, but sometimes conception date or IVF transfer date is the best anchor. This calculator supports all three approaches so you can estimate the due date, see where the pregnancy falls now, and review key milestones in one place.

Dating Method
Pick the pregnancy date you know most confidently. You can switch methods anytime.
Which date do you know best?

LMP is the standard clinical dating method. Conception and IVF are useful when they are more precise.

Enter Your Date
Use the one anchor date you trust most. IVF mode supports both 3-day and 5-day transfers.

Best when you know the cycle start date but not the exact conception timing.

Keep 28 days unless your cycle is consistently shorter or longer.

Optional Comparison
Compare a second known date against your primary estimate to see how much the timeline shifts.
Compare with another date?

Useful when you know both LMP and conception timing, or when you want to compare IVF dating with another anchor.

Results
Start with the date you know best

Choose the pregnancy date you trust most, then enter that one date to see the estimated due date, current pregnancy week, and next milestone.

  • Use LMP if the first day of your last period is the clearest starting point.

  • Use conception date when timing is known more confidently than cycle start.

  • Use IVF transfer date when transfer day and embryo age are the most precise details you have.

Related Calculators
Ovulation Calculator
Track fertility windows, ovulation dates, and mens...
Pregnancy Weight Gain Calculator
Track healthy weight gain during pregnancy with tr...
BMI Calculator
Calculate your Body Mass Index to determine if you...

How To Use the Due Date Calculator

What This Due Date Calculator Estimates

Most pregnancies are dated from the first day of the last menstrual period because clinical pregnancy weeks are counted from that point, not from actual conception. That can feel counterintuitive, especially when you know a conception or IVF transfer date more precisely than the cycle start.

This calculator bridges those dating methods. It converts the date you know into an estimated due date, current pregnancy week, trimester, and a short list of milestone dates you can use as planning references.

How To Use the Due Date Calculator

  1. Choose the dating method that best matches the most reliable information you have: LMP, conception date, or IVF transfer date.

  2. If you use LMP mode, enter the first day of the last period and adjust cycle length when your cycle is regularly longer or shorter than 28 days.

  3. If you use IVF mode, enter the transfer date and embryo age at transfer so the calculator can back into the estimated conception and LMP dates.

  4. Review the due date, current pregnancy week, trimester, and milestone table together rather than relying on the due date alone.

How the Calculation Works

LMP due date ≈ LMP + 280 days; conception due date ≈ conception + 266 days; IVF due date ≈ transfer date + (266 - embryo age in days)

LMP mode uses the standard 280-day pregnancy model, then adjusts the due date by the difference between your cycle length and a 28-day cycle. Conception mode uses the standard 266-day interval from conception to due date, then reconstructs an estimated LMP so the pregnancy week can still be expressed the usual clinical way.

IVF mode treats transfer timing differently because embryo age is known. A 5-day transfer and a 3-day transfer do not use the same offset, which is why the embryo-age input matters.

When This Estimate Is Useful

Comparing dating methods

If you know both LMP and conception timing, you can compare how much the estimated due date shifts and decide which reference is more realistic to discuss with your clinician.

IVF planning and milestone tracking

IVF pregnancies often come with very precise transfer timing, so the milestone table helps translate that date into standard pregnancy-week language used in appointments and resources.

General planning

The output can help with leave planning, appointment timing, and understanding which trimester applies now, even when the exact due date may still change later.

How To Read the Result

Treat the due date as an estimate, not a promise. Full-term delivery spans a window, and clinical dating can be revised after ultrasound findings or other information.

The current pregnancy week and milestone table are often more practical than the due date itself because care discussions, screening windows, and trimester transitions usually follow gestational week language.

Pregnancy Dating Tips

  • Use the most reliable known date rather than trying to average several uncertain dates

  • Adjust cycle length in LMP mode only when your cycle is consistently longer or shorter than 28 days

  • Remember that IVF transfer dating depends on embryo age at transfer

  • Use milestone dates as planning references, not as substitutes for medical scheduling advice

  • Ask your clinician which date should be treated as official if later imaging changes the estimate

Medical Disclaimer

This calculator is informational only and does not replace prenatal care. Pregnancy dating and care decisions should be confirmed with a qualified healthcare professional, especially if ultrasound findings or cycle history differ from the estimate.

Frequently Asked Questions

4

Pregnancy week is usually counted from the first day of the last menstrual period, not from conception. That is why a conception-based due date still gets converted into an estimated LMP behind the scenes.

If your cycle is consistently longer or shorter than 28 days, ovulation may occur later or earlier than the standard model assumes. Adjusting cycle length helps shift the due-date estimate accordingly.

IVF mode uses the transfer date plus embryo age to estimate conception timing. That makes it more precise than a generic conception-date assumption when transfer details are known.

No. It gives a planning estimate only. Official pregnancy dating may be adjusted by your clinician based on ultrasound findings, cycle history, and other medical information.

Explore Related Calculators

Continue with closely related tools to compare results, double-check inputs, or plan the next step in the same workflow.