Planning for your baby’s arrival is an exciting journey. Our free Due Date Calculator helps you estimate your baby’s expected delivery date quickly and accurately. Whether you’re tracking a natural pregnancy due date, calculating an IVF due date, or simply checking your baby’s due date, this tool gives you the guidance you need to prepare with confidence.
Pregnancy Due Date Calculator
Use our free pregnancy due date calculator to estimate your baby’s due date from the first day of your last menstrual period (LMP) and your average menstrual cycle length.
Your results also include your estimated conception date, current gestational age, trimester, pregnancy progress and important pregnancy milestones.
Start by entering the first day of your last menstrual period (LMP).
This is an estimate. Only a healthcare professional can confirm your pregnancy dating.
Pregnancy timeline
Your estimated pregnancy dates
A due date calculated from your last menstrual period is only an estimate. Ultrasound dating may give a different result, particularly if your menstrual cycle is irregular or you are unsure of the date of your last period.
How Does the Pregnancy Due Date Calculator Work?
Our pregnancy due date calculator estimates your expected delivery date using the first day of your last menstrual period (LMP). Pregnancy is commonly dated from the first day of the LMP rather than from the date of conception.
For a 28-day menstrual cycle, the calculator estimates a pregnancy duration of approximately 280 days, or 40 weeks, from the first day of your last period. If your average cycle is longer or shorter than 28 days, the calculator adjusts the estimate accordingly.
How to Calculate Your Pregnancy Due Date
To estimate your baby’s due date, enter the day, month and year that your last menstrual period began. Then select your average menstrual cycle length and choose Get my due date.
The calculator will estimate your due date and provide additional information including your gestational age, estimated conception date, current trimester, pregnancy progress and important pregnancy milestones.
Pregnancy Due Date Formula
A commonly used method for estimating a pregnancy due date is based on approximately 40 weeks, or 280 days, from the first day of the last menstrual period.
Estimated Due Date = First Day of LMP + 280 Days
Because ovulation does not always occur at the same point in every menstrual cycle, this calculator also allows you to enter your average cycle length. The estimated due date is adjusted when your cycle is longer or shorter than 28 days.
What Does LMP Mean?
LMP stands for last menstrual period. For pregnancy dating, the important date is the first day of your last menstrual period.
Although conception usually occurs after the beginning of the menstrual cycle, pregnancy weeks are conventionally counted from the first day of the LMP. This is why someone may be described as several weeks pregnant even though conception occurred later.
How Many Weeks Is a Pregnancy?
A pregnancy is commonly estimated as approximately 40 weeks from the first day of the last menstrual period. Your estimated due date represents the 40-week point when calculated using a standard 28-day cycle.
The estimated due date should not be interpreted as the exact day your baby will be born. Your healthcare professional may update your estimated due date based on your medical history and ultrasound findings.
Pregnancy Trimester Guide
| Pregnancy Stage | Approximate Weeks |
|---|---|
| First trimester | Weeks 1–13 |
| Second trimester | Weeks 14–27 |
| Third trimester | Week 28 onward |
How Accurate Is a Due Date Calculator?
A pregnancy due date calculator provides an estimate, not a guaranteed delivery date. An LMP-based calculation can be less reliable when menstrual cycles are irregular, the date of the last period is uncertain, or ovulation occurred earlier or later than expected.
Ultrasound measurements and clinical assessment may provide your healthcare professional with additional information for determining or revising your estimated due date.
Why Might My Ultrasound Due Date Be Different?
Your ultrasound-based pregnancy dating may differ from an LMP-based estimate. This can happen because menstrual cycle length and the timing of ovulation vary between individuals and between cycles.
If your ultrasound gives you a different estimated due date, discuss which date should be used with your doctor, midwife or other qualified healthcare professional.
Pregnancy Due Date Calculator FAQs
How do I calculate my pregnancy due date?
Enter the first day of your last menstrual period and your average menstrual cycle length into the calculator above. For a standard 28-day cycle, the estimate is based on approximately 280 days from the first day of the LMP.
Can I calculate my due date without knowing my last period?
An LMP-based calculator requires the date your last menstrual period began. If you do not know that date, speak with a healthcare professional about other methods of pregnancy dating, including ultrasound assessment.
Does cycle length affect my estimated due date?
Yes. The standard calculation generally assumes a 28-day menstrual cycle. A longer or shorter cycle may change the estimated timing of ovulation, so this calculator adjusts the estimate according to the average cycle length you enter.
Is conception date the same as the start of pregnancy?
Not for gestational dating. Pregnancy weeks are conventionally counted from the first day of the last menstrual period, which normally occurs before conception.
Is my estimated due date the exact day my baby will be born?
No. A due date is an estimate used to help date and monitor a pregnancy. Your actual delivery date may be before or after the estimated due date.
Important Medical Disclaimer
This pregnancy due date calculator is provided for general informational and educational purposes only. Results are estimates and are not a substitute for professional medical advice, diagnosis or pregnancy care. Always discuss pregnancy dating and any health concerns with a qualified healthcare professional.