Pregnancy Due Date Calculator
Estimate your pregnancy due date from the first day of your last menstrual period (LMP), conception date, or IVF 5-day embryo transfer date. See your current week and day of pregnancy and trimester timeline.
About the Pregnancy Due Date Calculator
A pregnancy due date calculator estimates your projected delivery date (Estimated Date of Delivery, or EDD) based on the first day of your Last Menstrual Period (LMP) or the date of conception. The calculation follows clinical obstetrics standards based on Naegele's rule.
Naegele's rule assumes a typical 28-day menstrual cycle with ovulation occurring approximately 14 days after the start of menstruation. The calculation adds 280 days (40 full weeks, or 10 lunar months) to the first day of the last menstrual period. If your menstrual cycle is longer or shorter than 28 days, the calculator adjusts the due date by the corresponding difference.
A calculated due date is an educated medical estimate rather than an exact appointment. Only about 4% to 5% of infants arrive on their exact predicted due date; a healthy, full-term birth naturally occurs anywhere within a five-week window between 37 weeks and 42 weeks of gestation.
If the first day of your last period was May 12 with a typical 28-day cycle: Add 7 days (May 19), subtract 3 months (February 19), and advance the year by one. The estimated due date is February 16 of the following year.
Tips for best results
- An early first-trimester ultrasound (performed between weeks 8 and 13) provides the most medically reliable dating method by measuring crown-rump length.
- Adjust the calculation if you have irregular or extended cycles, as longer intervals delay ovulation relative to the start of your period.
- Use your calculated due date to schedule milestone prenatal screenings, obstetric appointments, and maternity leave timelines.
How to use the Pregnancy Due Date Calculator
Why use Toolseza for Pregnancy Due Date Calculator?
Use this tool as often as you need with no paywalls, premium tiers, or hidden daily calculation quotas.
All calculations and file manipulations run inside your web browser. Your inputs are never sent to a cloud server.
Results update in real-time as you type or adjust settings, with instant one-click copy and export capabilities.
Works natively on smartphones, tablets, laptops, and desktop computers with zero installation or account creation.
Editorial Standards & Verification: All formulas, algorithms, and conversion factors implemented on Toolseza adhere to openly documented international standards (ISO, NIST, BIPM, W3C). Results are verified against benchmark reference datasets before publication.
Frequently Asked Questions
How is the pregnancy due date calculated?
By standard Naegele’s rule, the estimated due date is 280 days (40 weeks) from the first day of your last menstrual period (LMP), adjusted for your cycle length.
Does it support IVF transfer dates?
Yes — select the IVF 5-Day Transfer tab to calculate your due date 261 days from a 5-day blastocyst transfer.