Inputs
Explicit calculate flowPregnancy estimate panel
Choose your reference method, enter the matching date, and review the due date, pregnancy week, and trimester milestones.
Health toolDue date estimate
Due Date Calculator
Use this calculator to estimate a due date from the first day of your last period, a known conception date, or an IVF transfer date. It is a planning tool, not a diagnosis.
What you will get
Clear input, result, and explanation in one place
Due date estimate
The result shows the estimated due date, current pregnancy week, conception date, trimester milestones, and the full-term window.
This is a planning estimate only. Irregular cycles, IVF clinic conventions, and early ultrasound dating can all change the result.
Calculator
Enter your values and review the result
Result
Due date estimate
Result
Pregnancy timeline estimate
LMP-based estimate
Due month: January 2027
Estimated due date
11 Jan 2027
Current pregnancy week + day
1 week + 6 days
Calculated from the adjusted last period date you entered.
Estimated conception
20 Apr 2026
The reference date used for the due date estimate.
Second trimester
6 July 2026
Usually the 13-week transition point.
Third trimester
19 Oct 2026
Usually the 28-week transition point.
Full-term window
4 Jan 2027 to 17 Jan 2027
A practical full-term range is 39 weeks through 40 weeks + 6 days.
Pregnancy timeline
01
Estimated conception
20 Apr 2026
The date is shifted from your last period by the selected cycle length.
02
Second trimester
6 July 2026
This is the common 13-week transition point.
03
Third trimester
19 Oct 2026
This is the common 28-week transition point.
04
Full-term window
4 Jan 2027 to 17 Jan 2027
Full term is usually treated as 39 weeks through 40 weeks + 6 days.
05
Estimated due date
11 Jan 2027
A 40-week estimate adjusted for the cycle length you entered.
How to read this
Use the estimate as a planning tool. Calendar methods are most reliable when the date you entered is accurate, cycles are steady, and the pregnancy is not already being dated by an early ultrasound.
Due date calculators give planning estimates, not a diagnosis. They work best when the first day of the last period is known and cycles stay fairly regular. Early ultrasound dating can be more accurate.
Overview
What a due date calculator does
A due date calculator gives you an estimate of when a pregnancy is expected to reach about 40 weeks. It helps you plan ahead, compare dates, and keep important milestones in view without pretending the result is exact.
LMP method
How due date is estimated from your last period
The most common method uses the first day of your last menstrual period and adds a typical pregnancy length. When the cycle is not exactly 28 days, the estimate shifts slightly so the date better matches the cycle you entered.
Cycle length
Why cycle length matters
A longer cycle usually means ovulation happens a little later, so the estimated due date moves with it. A shorter cycle can pull the estimate forward. The adjustment is small, but it keeps the result closer to your real cycle pattern.
Conception timing
How conception date changes the estimate
If you know the most likely conception date, the calculator can skip the calendar guess and work from that date instead. That usually gives a cleaner estimate because it starts from a more specific point in the timeline.
IVF method
IVF due date calculation basics
IVF dating uses the transfer date and the embryo age from the clinic. Because the embryo age is known more precisely than a general calendar guess, the estimate is usually more structured than an LMP-only calculation.
Ultrasound
Why ultrasound dating can be more accurate
Early ultrasound can be more accurate than a calendar estimate because it measures the pregnancy itself rather than relying on cycle assumptions. If a clinic gives you an ultrasound-based date, that reference may be more useful than a calculator result.
Definitions
What full term means
Full term is commonly described as the period from 39 weeks through 40 weeks and 6 days. A due date calculator is useful because it shows that range instead of only a single day.
Accuracy
How accurate due dates really are
Even a careful estimate can move as the pregnancy is monitored. The calculator is best treated as a planning tool for appointments, milestones, and conversations, not as a promise that labor will happen on one exact day.
When to get help
When to speak with your doctor or midwife
If your cycles are very irregular, the dates do not match what you expected, or you have concerns about the pregnancy timeline, a doctor or midwife can help interpret the result. Their advice should take priority over any calculator estimate.
Common questions
It is a helpful estimate, but it can move if your cycle is irregular or if an early ultrasound gives a more precise date.
The calculator starts from the first day of your last period and adds a typical pregnancy length, then adjusts for cycle length if needed.
The estimate shifts a little so it matches the cycle length you entered instead of assuming a 28-day cycle for everyone.
Yes. If you know the likely conception date, that method usually gives a more direct estimate than starting from your last period.
Often yes, especially early in pregnancy, because ultrasound can date the pregnancy more directly than a calendar estimate.
Full term is commonly described as the range from 39 weeks to 40 weeks and 6 days.
You can use it as a rough guide, but irregular cycles make calendar estimates less reliable.
Yes. IVF usually uses the transfer date and embryo age, which gives a more specific starting point for the estimate.
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