Free Due Date Calculator: Track Conception, Due Date, and Growth Milestones

Due Date Calculator: Estimate Your Baby’s Arrival in Seconds

What it is

• A quick online tool that estimates an expected delivery date (EDD) from pregnancy inputs.

Common inputs

• Last Menstrual Period (LMP): most common; EDD = LMP + 280 days (40 weeks).
• Conception Date: adds 266 days (38 weeks) from conception.
• Ultrasound / Crown–Rump Length (CRL): used when LMP is uncertain; gives more accurate early estimates.
• Cycle length adjustment: if cycle ≠28 days, calculators shift the LMP-based estimate accordingly.

How it works (simple logic)

1. Start with the chosen date (LMP, conception, or ultrasound estimate).
2. Add the standard pregnancy length (typically 280 days from LMP or 266 from conception).
3. Apply corrections for cycle length or ultrasound dating if provided.
4. Output EDD, current gestational age (weeks + days), and trimester breakdown.

Accuracy & limitations

• Typical accuracy: LMP-based estimates assume ovulation at day 14; accuracy varies with cycle regularity.
• Best accuracy: early first-trimester ultrasound is most reliable for dating.
• Limitations: does not predict labor timing; only ~5% of births occur on the exact EDD. Medical factors (fertility treatments, irregular cycles, growth issues) can alter timing.

Useful outputs

• Estimated Due Date (EDD)
• Current gestational age (weeks + days)
• Trimester and milestone dates (anatomy scan, viability, full term)
• Estimated conception window

When to consult a clinician

• If periods are irregular, conception was via assisted reproduction, or ultrasound dating conflicts with LMP—ask your healthcare provider for final dating and prenatal plan.