Calculation Method
days
Home › Health & Fitness › Pregnancy Due Date Calculator
Estimate your baby’s due date based on your last menstrual period, known conception date, or IVF transfer date. Get a gestational age and trimester breakdown alongside your estimated due date.
Pregnancy Due Date Calculator — ToolPremier — For informational purposes only. Always consult your healthcare provider.
Select from three input options: Last Menstrual Period (LMP), a known conception date, or IVF transfer date (with separate options for Day 3 and Day 5 embryo transfers).
Input the relevant date and, if using LMP, your average cycle length in days (default is 28 days). The calculator adjusts the estimated ovulation and conception window accordingly.
The tool applies Naegele’s Rule or the appropriate IVF formula to return your Estimated Due Date (EDD) along with your current gestational age in weeks and days and your trimester.
The most common method is Naegele’s Rule, which adds 280 days (40 weeks) to the first day of your last menstrual period. This assumes a standard 28-day cycle with ovulation on day 14. If your cycle length differs, the estimated conception window is adjusted. When using a known conception date, 266 days (38 weeks) are added instead. For IVF, the formula depends on whether a Day 3 or Day 5 blastocyst embryo was transferred, with the dates adjusted accordingly.
The estimated due date is just that — an estimate. Only around 5% of babies are born on their exact calculated due date. Most births occur within a two-week window either side of it. The most reliable dating method is an early ultrasound scan conducted between 8 and 13 weeks of pregnancy, which measures the foetus directly. Your healthcare provider will confirm your due date using scan measurements and may adjust the LMP-based estimate if there is a significant discrepancy.
Naegele’s Rule assumes a 28-day cycle with ovulation on day 14. If your cycle is longer — for example, 35 days — ovulation likely occurs around day 21, shifting the estimated conception date and due date forward. This calculator allows you to enter your actual average cycle length to adjust for this difference. However, because cycle length varies month to month for many people, the result remains an estimate. An early ultrasound provides the most accurate dating regardless of cycle length.
No. This calculator is an informational tool that provides a general idea of your expected due date and current gestational stage. It cannot account for pregnancy complications, irregular cycles, or conditions that affect accurate dating. All due date estimates should be confirmed and monitored by a qualified healthcare provider. Do not make clinical decisions based solely on the output of any online calculator.
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The Pregnancy Due Date Calculator helps expectant parents estimate when their baby is likely to be born, based on their last menstrual period, conception date, or IVF transfer information. It is commonly used as a first step after a positive pregnancy test, providing a gestational week count and trimester classification alongside the estimated due date. The tool supports multiple input methods to accommodate different situations and cycle lengths.
No dates or personal details entered into this tool are transmitted anywhere; all calculations happen locally in your browser and are never stored or shared.