Pregnancy timeline planning tool
Pregnancy Due Date Calculator
Estimate your due date from the first day of your last menstrual period. See your current pregnancy week, trimester, time remaining, arrival period, and next major milestone.
Your pregnancy timeline
A useful timeline from one date.
Select the first day your last period began. The optional cycle-length adjustment is preset to 28 days, and all calculations stay in this browser.
Estimated due date
Monday, March 15, 2027
Based on the first day of your last period and a 28-day cycle.
54%complete
Pregnancy age18 weeks, 4 daysCycle-adjusted estimate
Current trimesterSecond trimesterWeek 5 of this trimester
Time remaining21 weeks, 3 daysUntil the estimated due date
Baby development phaseFetal growth stageWeeks 15–27: growth and movement develop through the middle part of pregnancy.
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0–3
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4–10
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11–14
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15–27
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28–36
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37+
40-week pregnancy timelineToday · week 18
Week 0Week 14Week 28Week 37Due · 40Week 42
Estimated arrival periodFebruary 22 – March 29, 2027Calendar span from week 37 through week 42.
Next milestoneThird trimester begins January 4, 2027In 9 weeks and 3 days.
You are currently in the second trimester. The displayed date is an estimate and may be revised after clinical assessment or ultrasound.
How to useEnter the first day of your last menstrual period, review the cycle length, and use the result to understand your estimated current and future pregnancy timeline.
Select the start dateChoose the first day your last menstrual period began, not the final day.
Review cycle lengthKeep 28 days or enter your usual average cycle from 21 to 45 days.
CalculateGenerate the estimated due date using the selected date and cycle length.
Review the timelineSee pregnancy age, trimester, time remaining, arrival period, and next milestone.
Use the resultPreview, print, or save the report; discuss clinical dates with a qualified healthcare provider.
What your result meansThe calculator keeps the main result compact while the report expands the current position, future milestones, planning worksheet, calculation method, and limitations.
Weeks 0–13First trimesterPregnancy dating begins from the first day of the last menstrual period.
Weeks 14–27Second trimesterThe calculator changes trimester automatically at the start of week 14.
Week 28 onwardThird trimesterThe current-position result continues through the estimated due date.
Weeks 37–42Arrival periodThe visual highlights a broad calendar span, not a guaranteed delivery date.
FormulaThe standard estimate adds 280 days to the first day of the last menstrual period. The optional adjustment shifts the estimate according to cycle length.
Standard
Estimated due date = LMP + 280 days
Adjusted
Estimated due date = LMP + 280 + (cycle length − 28) days
Pregnancy age
Today − cycle-adjusted pregnancy start
Worked example: A 30-day average cycle adds 2 days to the standard estimate. A 26-day average cycle subtracts 2 days.
Clinical priority: When a healthcare provider provides or revises an official estimated due date, use that clinical date instead of repeatedly recalculating from menstrual information.
Tips and common mistakesCorrect date entry is more useful than adding extra questions. These checks keep the result focused and reduce misleading precision.
Practical tips
- Use the first day your last period began.
- Enter your usual average cycle length, not one unusual cycle.
- Read pregnancy age in weeks and days rather than approximate months.
- Save the date on which the report was generated.
- Record a clinician-confirmed due date separately.
- Keep pregnancy dates private when using shared devices.
Common mistakes
- Entering the final day of the period.
- Entering period duration as cycle length.
- Using an uncertain date without acknowledging the uncertainty.
- Confusing gestational age with time since conception.
- Treating the due date as an exact delivery date.
- Continuing to use the estimate after a clinician revises it.
- Using this calculator for IVF treatment dates.
Frequently asked questionsFocused answers about due-date calculation, cycle adjustment, pregnancy weeks, ultrasound dating, and when a separate calculator is needed.
The standard estimate adds 280 days, or 40 weeks, to the first day of the last menstrual period. The optional cycle-length adjustment adds or subtracts the difference from 28 days.
Gestational age is conventionally counted from the first day of the last menstrual period, so the timeline begins before fertilization would usually occur.
No. It is a planning estimate. The actual delivery date can occur before or after it, and a healthcare provider may revise the estimate.
Enter your usual average cycle length. A longer cycle shifts the estimate later, while a shorter cycle shifts it earlier.
A menstrual-period estimate may not be reliable without a known start date. Discuss pregnancy dating with a qualified healthcare provider.
Clinical assessment or ultrasound may provide a more appropriate estimate, especially when menstrual information or cycle timing is uncertain.
No. IVF due dates use treatment-specific dates and belong in a separate IVF Due Date Calculator.
No. It only creates an estimated timeline from the date and cycle length entered.