Pregnancy Due Date Calculator
Estimate your due date & track your pregnancy journey
Uses standard pregnancy dating methods. Results are estimates and should not replace medical advice.
Supports LMP, Conception, IVF, Ultrasound
Your Pregnancy Journey
Baby's size: —
This Week's Development
—
—
Next Milestone
—
Upcoming Milestones
- Week 8: Major organs continue developing
- Week 12: End of first trimester
- Week 20: Anatomy scan
- Week 24: Baby begins responding to sounds
- Week 37: Full term approaches
How Your Due Date Is Calculated
Based on the first day of your last menstrual period (LMP), your average cycle length, or another selected method. Pregnancy is commonly estimated as 40 weeks (280 days) from the first day of the last menstrual period. This calculator uses widely accepted obstetric guidelines.
| Method | Description |
|---|---|
| Last Menstrual Period (LMP) | Estimates pregnancy as 40 weeks from the first day of the last menstrual period. |
| Conception Date | Estimates due date from the known conception date. |
| IVF Transfer | Uses embryo transfer date to estimate due date. |
| Ultrasound | Uses fetal measurements to estimate gestational age. |
Real Example
If LMP is January 1, 2026, with a 28-day cycle, the estimated due date is October 8, 2026.
Limitations
This calculator provides an estimated due date based on the information entered. It cannot account for every pregnancy, including differences identified during ultrasound or individual medical circumstances. Your healthcare provider may recommend a different due date based on clinical evaluation.
References
- American College of Obstetricians and Gynecologists (ACOG)
- National Health Service (NHS)
- World Health Organization (WHO)
- Mayo Clinic
- MedlinePlus
Trust & Privacy
Designed for desktop and mobile devices, with keyboard-accessible controls and clearly labeled form fields.
Frequently Asked Questions
Due dates are estimates. Only 5% of babies are born on their exact due date. Your healthcare provider may adjust based on ultrasound.
LMP is the most common method if you have regular cycles. Ultrasound dating is more accurate in early pregnancy.
Yes, your healthcare provider may adjust your due date based on ultrasound measurements, especially in the first trimester.
Yes, IVF due dates are calculated from the embryo transfer date, adjusted for the age of the embryo at transfer.
Because conception dates are often unknown, healthcare providers use the first day of your last menstrual period as a consistent starting point.
Yes, the calculator uses a default 28-day cycle. For more accuracy, enter your average cycle length if you know it.
🌸 © 2026 CalculatorKits — Pregnancy Due Date Calculator · For educational use only
Pregnancy Calculator: Calculate Your Due Date and Pregnancy Timeline
Finding out that you are pregnant often brings one immediate question: when is my baby due? A Pregnancy Calculator gives you a quick way to estimate your due date and understand where you are in your pregnancy.
The CalculatorKits Pregnancy Calculator is designed to provide more than a single date. The current tool lets you select a dating method and enter information such as the first day of your last menstrual period, average cycle length, ultrasound gestational age, or IVF transfer details, depending on the method selected. The result can show an estimated due date, pregnancy week, days remaining, trimester, and pregnancy milestones.
Pregnancy dating can seem confusing because medical pregnancy age usually starts from the first day of the last menstrual period rather than the actual day of conception. A standard estimate is about 40 weeks or 280 days from the first day of the last menstrual period. ACOG also recommends using the best available clinical information when establishing the estimated due date.
Your due date is an estimate, not a guarantee of the day your baby will arrive. This guide explains how the CalculatorKits tool works, how to use it step by step, why due dates can change, and how to understand your result.
Quick Answer
A Pregnancy Calculator estimates your due date and pregnancy progress using a selected dating method.
For the standard last menstrual period method:
Estimated due date = First day of last menstrual period + 280 days
The CalculatorKits tool supports:
- Last menstrual period
- Conception date
- IVF transfer
- Ultrasound dating
It can show:
• Estimated due date
• Current pregnancy week
• Pregnancy day
• Days until due date
• Trimester
• Pregnancy progress
• Upcoming milestones
The result is an educational estimate. Your healthcare provider may establish a different official due date after reviewing your medical history and ultrasound findings.
What Is a Pregnancy Calculator?
A Pregnancy Calculator is an online date calculation tool that estimates how far pregnancy has progressed and when the baby may be due.
The most common starting point is the first day of the last menstrual period, often called LMP. This date is usually easier to identify than the exact day of conception, so it provides a practical starting point for pregnancy dating.
Using LMP dating, pregnancy is counted as about 40 weeks. That can feel unusual because conception generally happens later in the menstrual cycle.
This means gestational age is not the same as the amount of time since conception.
The CalculatorKits tool simplifies this process and also supports other dating information when it is available.
Why Use a Pregnancy Calculator?
A Pregnancy Calculator is useful when you want a quick answer without counting dates manually.
You may want to know:
• When your baby is approximately due
• How many weeks pregnant you are
• How many days remain
• Which trimester you are in
• What milestone may be approaching
• How pregnancy dates fit into your calendar
The CalculatorKits result provides a pregnancy journey instead of stopping at a single estimated date. This gives you a simple overview of your pregnancy progress.
How Does the Pregnancy Calculator Work?
The method depends on the option you select.
Last Menstrual Period
The standard method starts with the first day of your last menstrual period. Pregnancy is commonly estimated as 280 days from that date.
CalculatorKits also includes an average cycle length field. This can be useful when your cycle is consistently shorter or longer than 28 days. The NHS likewise allows cycle length adjustment in its due date calculator.
Conception Date
If your approximate conception date is known, a due date can be estimated from that date. A typical pregnancy is about 266 days from conception.
IVF Transfer
Pregnancies resulting from assisted reproductive treatment can use embryo transfer information and embryo age for dating. ACOG recommends using assisted reproductive technology derived gestational age when assigning the estimated due date.
Ultrasound
The CalculatorKits tool can also use gestational age measured at an ultrasound. In clinical care, first trimester ultrasound is considered the most accurate method for establishing or confirming gestational age.
How to Use the Pregnancy Calculator
- Open the CalculatorKits Pregnancy Calculator and review the information above the input fields.
- Select the calculation method that matches the information you have.
- For the LMP method, enter the first day of your last menstrual period.
- Enter your average cycle length when the selected method requests it.
- For ultrasound dating, enter the ultrasound date and gestational age measured at that scan.
- For IVF dating, enter the transfer information and embryo age requested by the tool.
- Check all dates carefully before calculating.
- Click Calculate Due Date.
- Review your estimated due date and pregnancy progress.
- Check your pregnancy week, days remaining, trimester, and milestone information.
- Compare the estimate with the due date provided by your healthcare professional.
If you are unsure about your last menstrual period, do not create false precision by guessing an exact date.
How Is a Pregnancy Due Date Calculated?
The traditional LMP calculation is:
Estimated due date = LMP + 280 days
That equals approximately 40 weeks.
A traditional calendar method, commonly called Naegele’s rule, adds seven days to the first day of the last menstrual period, counts back three months, and adjusts the year.
For example, if your last period began on January 10, the estimated due date would be around October 17.
This approach assumes a typical cycle and ovulation pattern. ACOG notes that LMP dating can be affected by inaccurate recall, irregular cycles, and variation in ovulation timing.
How Is Pregnancy Counted as 40 Weeks?
Pregnancy is usually dated from the first day of the last menstrual period rather than conception.
In a typical 28 day cycle, ovulation and conception often occur around two weeks after the period begins.
So someone who is four weeks pregnant may have conceived roughly two weeks earlier.
This is a standard part of gestational dating.
It does not mean the baby has been developing for four full weeks since conception.
What Is Gestational Age?
Gestational age describes how far pregnancy has progressed according to the dating method being used.
It is normally expressed in weeks and days.
For example, 10 weeks and 4 days means approximately ten completed weeks plus four additional days.
Healthcare professionals use gestational age to organize prenatal care and discuss pregnancy development.
The CalculatorKits pregnancy timeline uses the same concept to show your current pregnancy week and day.
What Is an Estimated Due Date?
An estimated due date is the date when pregnancy is expected to reach about 40 weeks according to the selected dating method.
The key word is estimated.
The NHS states that pregnancy normally lasts between 37 and 42 weeks from the first day of the last menstrual period.
The due date is therefore a useful reference point rather than an exact prediction.
Will My Baby Arrive on the Due Date?
You should not expect your baby to arrive exactly on the estimated due date.
Some babies arrive earlier.
Others arrive later.
The estimated date gives your healthcare provider a reference point for monitoring pregnancy and planning care.
Cleveland Clinic notes that the due date is only an estimate and that only a small percentage of babies are born exactly on that date.
A Pregnancy Calculator cannot predict the exact day labor will begin.
Why Can My Due Date Change?
Your due date can change when better dating information becomes available.
An early ultrasound is an important example. ACOG considers first trimester ultrasound the most accurate method for establishing or confirming gestational age.
Your dating may also be reviewed when:
• Your LMP is uncertain
• Your cycles are irregular
• Your cycle is consistently shorter or longer than 28 days
• Ultrasound dating differs from menstrual dating
• Your pregnancy resulted from IVF or another assisted reproductive treatment
A revised due date does not necessarily mean the first calculation was wrong. It may simply mean better information is now available.
What If I Do Not Know My Last Menstrual Period?
Not everyone remembers the exact date.
This may happen because of irregular periods, recently changing contraception, or simply not recording the date.
You can still use a Pregnancy Calculator for a rough estimate, but the result is less reliable when the starting date is uncertain.
The NHS advises speaking with a midwife or GP if you do not know or are unsure of the first day of your last period.
An ultrasound may then provide better information for pregnancy dating.
What If My Cycle Is Longer or Shorter Than 28 Days?
Not everyone has a 28 day cycle.
A consistently longer or shorter cycle can shift ovulation and affect an LMP based due date estimate.
The CalculatorKits tool includes an average cycle length field. Enter your usual cycle length when you know it.
The NHS also recommends adjusting for cycle length when it differs from 28 days.
If your cycles are very irregular, discuss your dates with your healthcare provider.
Pregnancy Calculator and Conception Date
A conception based calculation can be useful when the approximate conception date is known.
A typical pregnancy is about 266 days from conception.
The difficulty is that the exact day of conception is often uncertain in a natural pregnancy. Ovulation can vary and fertilization does not necessarily occur on the day of intercourse.
For this reason, LMP and ultrasound information are commonly used for routine pregnancy dating.
If you want to explore conception timing separately, use the Pregnancy Conception Calculator.
Pregnancy Calculator and IVF
IVF pregnancies can be dated using embryo age and transfer date.
This can be more precise than estimating pregnancy timing from an uncertain menstrual period.
ACOG recommends using assisted reproductive technology derived gestational age when assigning the estimated due date.
If you conceived through IVF, use the dating information provided by your fertility clinic.
Pregnancy Trimesters
Pregnancy is commonly divided into three trimesters.
First Trimester
The first trimester extends through 13 weeks and 6 days.
Second Trimester
The second trimester begins at 14 weeks and continues through 27 weeks and 6 days.
Third Trimester
The third trimester begins at 28 weeks and continues until birth.
The CalculatorKits timeline can help you see where you are within this general progression.
What Information Does the Calculator Show?
The CalculatorKits pregnancy result is designed to provide more than a single date. The current page can show:
• Estimated due date
• Current pregnancy week
• Pregnancy day
• Days until due date
• Current trimester
• Pregnancy progress
• Baby development information
• Next milestone
• Upcoming milestones
It also presents a visual 40 week pregnancy timeline.
Milestone information is general education. It should not be used to determine whether your individual pregnancy is developing normally.
How Accurate Is a Pregnancy Calculator?
A Pregnancy Calculator can perform the date calculation correctly, but the estimated date depends on the information entered.
LMP dating can be less reliable when the date is uncertain or cycles are irregular.
First trimester ultrasound provides a more reliable clinical estimate. ACOG considers first trimester ultrasound the most accurate method for establishing or confirming gestational age.
This means mathematical accuracy and pregnancy dating accuracy are not exactly the same.
The calculator can correctly add the required number of days while the starting date itself may still involve uncertainty.
Why Can Two Pregnancy Calculators Give Different Dates?
Different calculators can use different methods.
One may use only LMP.
Another may adjust for cycle length.
Another may include conception, IVF, or ultrasound dating.
Even two LMP calculators can differ when they use different cycle assumptions.
Before comparing results, check the method being used.
For medical care, follow the pregnancy dating established by your healthcare provider.
Common Mistakes When Using a Pregnancy Calculator
Entering the Wrong LMP Date
A date error can shift the estimated due date.
Confusing LMP With Conception
The first day of your last period is not the same as the day conception occurred.
Guessing an Uncertain Date
If you are unsure, tell your healthcare provider.
Ignoring Cycle Length
A consistently shorter or longer cycle can affect an LMP based estimate.
Assuming 40 Weeks Means an Exact Delivery Date
Forty weeks is a standard dating estimate, not a guarantee.
Ignoring Early Ultrasound Dating
Clinical ultrasound information may provide a better estimate.
Using the Calculator to Assess Symptoms
A Pregnancy Calculator cannot determine whether bleeding, pain, fluid leakage, reduced movement, or another symptom is normal.
How to Get a Better Pregnancy Due Date Estimate
Use the best dating information available.
Keep a record of the first day of your last menstrual period.
Know your average cycle length when it is consistent.
Keep your ultrasound information available.
If you used IVF, save your embryo transfer date and embryo age.
When your healthcare provider establishes an official estimated due date, use that date for medical care.
An online calculator is most useful for understanding and planning around your pregnancy timeline.
Pregnancy Calculator for Planning
Knowing an estimated due date can make pregnancy planning easier.
You can use the timeline to:
• Mark an approximate due date
• Understand your current pregnancy week
• Follow general pregnancy information
• Prepare questions for appointments
• Track upcoming milestones
• Plan personal and family arrangements
Stay flexible because your due date can be revised when better clinical information becomes available.
When Should You Contact Your Healthcare Provider?
A Pregnancy Calculator only calculates dates. It cannot assess pregnancy symptoms.
Contact your healthcare provider if you have concerns such as:
• Vaginal bleeding
• Severe abdominal or pelvic pain
• Fluid leaking from the vagina
• Severe headache or vision changes
• Fever or feeling seriously unwell
• Reduced fetal movement later in pregnancy
• Any symptom that concerns you
Seek urgent medical help for severe or emergency symptoms.
Do not use a calculator result to decide that a concerning symptom can safely wait.
Frequently Asked Questions
What is a Pregnancy Calculator?
A Pregnancy Calculator is an online tool that estimates your due date and pregnancy timeline from pregnancy dating information.
How does a Pregnancy Calculator calculate the due date?
The traditional LMP method adds about 280 days or 40 weeks to the first day of the last menstrual period.
What does LMP mean?
LMP means last menstrual period and normally refers to the first day of your most recent menstrual period before pregnancy.
Is the due date exact?
No. The due date is an estimate. Babies can be born before or after the estimated date.
Can my due date change after an ultrasound?
Yes. Your healthcare provider may revise the due date when ultrasound provides better dating information, especially during the first trimester.
What if I do not know my LMP?
Speak with your healthcare provider. An early ultrasound may provide a better estimate.
What if my cycle is not 28 days?
A longer or shorter cycle can affect the estimate. Enter your average cycle length when the calculator provides that option.
Can I calculate my due date from conception?
Yes, when the conception date is reasonably known. A conception based estimate is generally about 266 days from conception.
How does IVF pregnancy dating work?
IVF dating uses embryo age and transfer information and can provide a more precise dating method when those details are known.
Can a Pregnancy Calculator predict labor?
No. It can estimate a due date but cannot predict the exact day labor will begin.
Can it tell me whether my baby is healthy?
No. A date calculation cannot assess fetal health, growth, or pregnancy complications.
Can a Pregnancy Calculator tell me my baby’s sex?
No. Pregnancy dating does not determine fetal sex.
How often should I use a Pregnancy Calculator?
You usually do not need to recalculate every day. Recheck your information if you entered a date incorrectly or your healthcare provider gives you updated dating.
Key Takeaways
A Pregnancy Calculator provides a convenient way to estimate your due date and understand your pregnancy timeline.
The standard LMP method uses about 280 days or 40 weeks from the first day of the last menstrual period.
The CalculatorKits tool can also support conception, IVF, and ultrasound dating.
Your estimated due date is not an exact prediction of the delivery date.
Cycle length and the accuracy of your LMP can affect the estimate.
First trimester ultrasound is the most accurate method for establishing or confirming gestational age when appropriate.
The CalculatorKits result can show pregnancy week, days remaining, trimester, progress, and milestones.
Use the calculator for general education and planning.
For official pregnancy dating and medical decisions, follow the advice of your healthcare provider.
Related CalculatorKits Tools
Pregnancy Weight Gain Calculator
Estimate pregnancy weight gain using your starting information and understand general changes during pregnancy.
Pregnancy Conception Calculator
Estimate a possible conception date from pregnancy dating information.
Due Date Calculator
Calculate an estimated due date using pregnancy dating information.
Ovulation Calculator
Estimate an approximate ovulation date from menstrual cycle information.
Fertile Window Calculator
Estimate the part of the cycle when conception is more likely.
Period Calculator
Estimate upcoming menstrual dates and track your cycle.
Pregnancy Week by Week Calculator
Explore general pregnancy development information based on gestational week.
Fetal Growth Calculator
Explore general fetal growth information using pregnancy dating and related measurements.
Contraction Timer
Track contraction timing and duration as you approach labor.
References
- American College of Obstetricians and Gynecologists: Methods for Estimating the Due Date
Guidance on LMP dating, ultrasound dating, assisted reproductive technology dating, and establishing the estimated due date. - NHS: Pregnancy Due Date Calculator
Explains LMP based due date calculation, cycle length adjustments, pregnancy duration, and the role of ultrasound. - Mayo Clinic: Pregnancy Due Date Calculator
Explains pregnancy dating and why the estimated due date is not an exact delivery date. - American College of Obstetricians and Gynecologists: How Your Fetus Grows During Pregnancy
Explains gestational age, pregnancy trimesters, due dates, and general fetal development. - American College of Obstetricians and Gynecologists: When Pregnancy Goes Past Your Due Date
Explains estimated due dates and what happens when pregnancy continues beyond the estimated date.
Medical Disclaimer
This article and the CalculatorKits Pregnancy Calculator are provided for general educational and informational purposes only. The calculator provides an estimated pregnancy timeline and due date and is not a substitute for prenatal care, ultrasound assessment, or professional medical advice. Pregnancy dating can vary depending on menstrual history, cycle length, conception timing, and other factors. If you are pregnant or think you may be pregnant, consult a qualified healthcare professional for appropriate prenatal care and confirmation of your pregnancy dating.
Written and reviewed by the CalculatorKits Editorial Team
Last Updated: September 6, 2026