How to use it
- Enter the first day of your last menstrual period.
- Click the Calculate button.
- Read the estimated due date and weeks along displayed.
What it does – The calculator adds 280 days to the first day of your last menstrual period, giving you an estimated due date and the pregnancy week count. Why it matters – Knowing the due date helps you schedule prenatal appointments, plan maternity leave, and prepare for baby arrivals. How to read the result – The due date is shown in month‑day‑year format; the weeks along tells you how many weeks have elapsed since the start of your last period, rounded down to the nearest whole week. No medical diagnosis is provided; use the estimate as a planning tool and confirm with your healthcare provider. The 280‑day rule, known as Naegele’s rule, is the standard method used by obstetricians worldwide. While individual cycles vary, this estimate is accurate for most pregnancies within a week. If your cycle is longer or shorter, you can adjust the start date accordingly, but the calculator keeps the calculation simple and fast. Remember to share the result with your midwife, and mark the date on your calendar to stay on track.
Pro tips
- Add a few days to account for irregular cycles.
- Round weeks down; pregnancy weeks start at 0.
- Print or screenshot the result for appointments.
- Double‑check the date format (MM/DD/YYYY) before sharing.
Real-life examples
- A first‑time mom wants to know when to book her 20‑week anatomy scan.
- A couple planning a maternity leave schedule needs the official due date.
- A healthcare provider needs a quick reference for a patient’s pregnancy timeline.
Case study
Emily entered Jan 5, 2024 as her last period start. The calculator gave her a due date of Oct 12, 2024 and showed she was 8 weeks pregnant, letting her book her anatomy scan and maternity leave well in advance.