WWorkmate

Due Date Calculator

Enter your last period to instantly see the due date, current pregnancy weeks, trimester, and days to go.

Due date

Estimated due date
2027-03-08

Days to go 269 days · Progress 3.9%

Current pregnancy
1weeks 4days
Trimester
1

Based on Naegele's rule (LMP + 280 days). Cycles other than 28 are auto-adjusted. The actual date is confirmed by ultrasound; term spans 37-42 weeks so the due date is an estimate.

What this tool does

The due date calculator estimates your delivery date from the last menstrual period (LMP). Based on Naegele's rule (LMP + 280 days), it shows the current pregnancy week, trimester, progress, and days to go, and auto-adjusts for cycles other than 28 days.

Who uses this

  • Calculate the due date after confirming pregnancy
  • Check current pregnancy week and trimester
  • Plan prenatal checkups and maternity leave
  • Adjusted due date for irregular cycles
  • Track pregnancy progress and D-day

How to use

  1. 1Enter the first day of your last menstrual period (LMP).
  2. 2Enter your average cycle length. Default is 28 days; otherwise ovulation timing is adjusted.
  3. 3See the due date, current week/trimester, progress, and days remaining.

Naegele's rule

EDD = LMP + 280 days (40 weeks) = LMP + 1 year − 3 months + 7 days Pregnancy weeks = (today − LMP) / 7 Trimester: 1st 0-13 wks, 2nd 14-27, 3rd 28+ Cycle adjustment: shift EDD by (cycle − 28) days e.g. 35-day cycle → EDD 7 days later

Real examples

Example 1: LMP Jan 1 (28-day cycle)

Jan 1 + 280 days = Oct 8 due date. Based on the 40-week full term.

Example 2: 20 weeks pregnant

140 days after LMP = 20 weeks = 2nd trimester. Anatomy scan and sex determination period. 50% progress.

Example 3: 35-day cycle

Later ovulation shifts the due date 7 days past the 28-day estimate. Cycle adjustment gives a more accurate date.

Frequently asked questions

Will I deliver exactly on the due date?+

It's an estimate. Full term spans 37-42 weeks, and only ~5% deliver on the exact due date. Most deliver within ±2 weeks.

Is it accurate with irregular cycles?+

Naegele's rule assumes a regular 28-day cycle. Irregular cycles increase error, so an ultrasound (fetal-size) due date is more accurate. This tool supports cycle adjustment but is for reference.

When does pregnancy week counting start?+

The first day of LMP is week 0 day 0. Actual conception is ~2 weeks later, but since exact ovulation is unknown, LMP is the standard. So 'week 4' is around the expected period date.

How are trimesters divided?+

1st 0-13 weeks (organ formation, nausea), 2nd 14-27 (stable, movement), 3rd 28+ (rapid growth, term prep). Each has different tests and precautions.

It differs from the ultrasound date — which is right?+

The early ultrasound (7-12 weeks) date is most accurate. If it differs from LMP by 1+ weeks, the ultrasound date is usually adopted. This tool estimates from LMP, so prioritize your OB-GYN's confirmed date.

Same due date for twins?+

Twins/multiples tend to be born earlier (usually before 37 weeks). This calculator assumes a singleton, so follow medical guidance for multiples.

Cautions

  • •Naegele's rule (LMP+280) estimate — ultrasound date is more accurate.
  • •Full term spans 37-42 weeks; ~5% deliver on the due date.
  • •Irregular cycles increase error.
  • •Twins/multiples tend to be earlier (separate).
  • •Confirm the exact date via OB-GYN ultrasound.

Last reviewed: 2026-05-30

Due Date Calculator — pregnancy weeks & trimester