Pregnancy Due Date Calculator

Pregnancy Due Date Calculator estimates a due date from the first day of the last menstrual period using Naegele's rule — 280 days after the LMP — adjusted for cycles longer or shorter than 28 days. It also shows the estimated gestational age in weeks and days and the number of days remaining, based on today's date on your device.

An estimated due date is a common first reference point for planning. Calculating it by hand means counting across months of different lengths and leap years; this tool does it with calendar-safe date arithmetic and shows the method so you can follow every step. Only a qualified healthcare professional can confirm a due date.

1. Select the first day of the last menstrual period.
2. Enter the usual cycle length in days, or keep the default of 28.
3. Press Estimate due date.
4. Read the estimated due date, gestational age and days remaining.
5. Copy or download the summary if you want to keep a record.

• Naegele's rule: LMP + 280 days, adjusted by cycle length minus 28
• Cycle lengths from 20 to 45 whole days, defaulting to 28
• Gestational age in weeks and days and days remaining from today
• Time-zone-safe calendar arithmetic that handles leap years and month lengths
• Rejects future dates, invalid dates and dates more than 44 weeks ago
• Copy and Download summaries with entered values, method and estimate

• Use the first day of full bleeding as the start of the last period.
• Enter an average cycle length if your cycles vary.
• Check that the date on your device is correct, as days remaining depend on it.
• Treat the result as an estimate and confirm dating with a healthcare professional.