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Home› Health Calculators› Pregnancy & Fertility› Pregnancy Due Date Calculator

Pregnancy Due Date Calculator
with LMP, Conception, IVF, IUI and Ultrasound Dating

Estimate a pregnancy due date from last menstrual period, conception date, ovulation, IVF transfer, embryo age, IUI, ultrasound dating or a known due date reverse check. Includes trimester dates and gestational age.

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Pregnancy Due Date Calculator
Method: Last menstrual period
📅
Classic due date estimate using Naegele-style counting from LMP.
days
Default is 28 days. Longer or shorter cycles shift the estimate.
Method: Conception date
📅
Used when conception timing is known more directly.
fx
Informational only. Does not change the core formula.
Method: Ovulation date
📅
Useful when ovulation is tracked by test, temperature or monitoring.
src
Informational only.
Method: IVF transfer
📅
Date embryo transfer took place.
days
Needed for IVF-specific due date logic.
type
Informational only.
Method: IUI date
📅
Date insemination took place.
trg
Informational only. Core estimate uses IUI date.
Method: Ultrasound dating
📅
Date of scan used for dating.
wks
Whole weeks at time of scan.
days
Extra days beyond full weeks.
Method: Known due date reverse check
📅
Use this to estimate the matching conception and LMP dates.
days
Used when reconstructing the implied LMP date.
Method note
LMP mode estimates due date from the first day of the last menstrual period and adjusts for cycle length when needed.
Estimated Due Date
—
based on selected dating method
Gestational Age Today
—
based on calculated pregnancy dating
Conception Date
—
estimated conception equivalent
LMP Equivalent
—
estimated pregnancy dating baseline
Weeks Remaining
—
time until estimated due date
End of 1st Trimester
—
Around 13 weeks 6 days.
Start of 3rd Trimester
—
Around 28 weeks 0 days.
Full Term Window
—
From 37 weeks 0 days to 40 weeks 0 days.
Dating summary
Method used—
Input date used—
Cycle length—
Embryo age / scan age—
Pregnancy summary
Due date—
Conception equivalent—
LMP equivalent—
Gestational age today—
Pregnancy Timeline
Milestone Date Pregnancy Age Note
Due Date Breakdown
Method selected—
Dating input—
Due date—
Conception equivalent—
LMP equivalent—
Gestational age today—
End of first trimester—
Start of third trimester—
Full term starts—
Estimated due date—
This calculator provides date estimates and does not replace clinical dating or medical advice. Ultrasound or clinician-provided dating can differ from LMP-based estimates and may be considered more accurate in some situations.
✦ Cal, AI Explanation
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Your due date estimate is ready. Ask me how the dating method works, why IVF dating differs from LMP dating, or what the trimester dates mean.

💡 Due Date Notes

LMP dating assumes pregnancy age starts before conception, which is why due date formulas count from the menstrual cycle.
Conception, ovulation, IUI and IVF methods can give more direct timing when those dates are known.
IVF dating depends on transfer date and embryo age at transfer.
Ultrasound dating uses gestational age on the scan date to reconstruct the expected due date.
Estimated dates are references, not guarantees of birth timing.

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Related Guides

How Due Date Calculators Work→ IVF Due Date Explained→ LMP vs Ultrasound Dating→

How due date dating works here

This calculator supports multiple pregnancy dating methods instead of only one. It can estimate a due date from last menstrual period, conception date, ovulation date, IVF transfer, IUI date, ultrasound dating, or from a known due date reverse check.

The method matters because pregnancy age is usually counted from a dating baseline that is earlier than conception. IVF and ultrasound methods can therefore produce more direct estimates when those data points are available.

Core date rules

LMP Due Date = LMP + 280 days + cycle adjustment
Conception / Ovulation / IUI Due Date = event date + 266 days
IVF Due Date = transfer date + (266 − embryo age) days
Ultrasound Due Date = scan date + [280 − gestational age at scan] days
Known due date reverse mode reconstructs the implied conception date and LMP equivalent from the entered due date.

Why IVF dating is different

IVF dating uses the transfer date and embryo age rather than relying on a menstrual-cycle estimate. A 5-day embryo transfer and a 3-day embryo transfer therefore use different offsets even when the transfer dates are the same.

This makes IVF due date estimation more specific when transfer details are known.

Method Main Input Dating Logic
LMPFirst day of last periodCounts from menstrual baseline
Conception / Ovulation / IUIKnown event dateCounts forward to 266-day due date
IVFTransfer date + embryo ageAdjusts for embryo age at transfer
UltrasoundScan date + gestational ageBack-calculates pregnancy dating

Ultrasound and reverse dating

Ultrasound dating starts with gestational age on the scan date and works forward to the estimated due date. Reverse mode does the opposite by starting with an existing due date and estimating what conception date or LMP equivalent would align with that due date.

These modes are useful when cycle-based dating is uncertain or when a clinic date is already available.

Frequently Asked Questions

Why can different methods give different due dates?+
Because each method starts from a different kind of information. LMP, conception, IVF transfer and ultrasound dating do not all measure the same point in the process, so the resulting due dates can differ.
How is IVF due date calculated here?+
The calculator uses the transfer date and embryo age at transfer. A 5-day embryo and a 3-day embryo do not use the same offset, which is why embryo age is required in IVF mode.
What does gestational age today mean?+
It is the pregnancy age today based on the dating baseline implied by the selected method. It is shown in weeks and days, not as time since conception alone.
Why does LMP mode ask for cycle length?+
Because the standard LMP method assumes a 28-day cycle. If the cycle is longer or shorter, the estimate is shifted to reflect that difference.
Is the due date exact?+
No. It is an estimate based on the dating information provided. Birth does not always occur exactly on the calculated due date.