Due Date Calculator

Estimate your pregnancy due date from last menstrual period or conception date. See gestational age and trimester instantly — free, private, educational.

Reviewed / updated August 4, 2026

Your inputs

days

28 days is the classic Naegele assumption; adjust if your cycles differ

Result

Estimated due date

February 19, 2027

12w 0d · First trimester

Gestational age
12 weeks, 0 days
Trimester
First trimester
Days until EDD
196

About 12 weeks along (first trimester). Estimated days until the due date: 196.

Suggested next steps

  • Confirm dating with your clinician — ultrasound dating can adjust the EDD.
  • Use the Date Difference Calculator if you need exact day counts between appointments.
  • This tool is educational — it does not replace prenatal care.

How the due date calculation works

From last menstrual period (LMP)
Estimated due date ≈ LMP + 280 days + (cycle length − 28).

From conception
Estimated due date ≈ conception date + 266 days.

The tool also estimates gestational age (weeks + days from an LMP-equivalent start), trimester, and days remaining until the EDD. Results update as you change dates. Rule-based tips describe trimester stage and remind you that clinical dating can differ.

Worked example

LMP = 1 January 2026, cycle length 28 days:

  1. 1 Jan + 280 days ≈ 8 October 2026 estimated due date
  2. On 4 August 2026, gestational age is roughly 30 weeks + 5 days (third trimester)

If conception were known as 15 January 2026, EDD ≈ 15 Jan + 266 days ≈ 8 October 2026 as well under these classic assumptions.

Methodology and notes

Calculations use calendar arithmetic in your browser. Irregular cycles, IVF dating, and early ultrasound measurements can change the official EDD. This is not medical advice.

Frequently asked questions

How is a due date calculated from LMP?

Naegele’s rule estimates the due date as the first day of the last menstrual period plus 280 days (40 weeks), with an adjustment when your average cycle is longer or shorter than 28 days.

What if I know the conception date instead?

Conception-based dating commonly adds about 266 days (38 weeks) from conception to estimate the due date. Ultrasound dating from your clinician may still refine that estimate.

How accurate is an estimated due date?

Only about 5% of babies arrive on the exact EDD. Most deliveries occur within about two weeks before or after. The date is a planning midpoint, not a guarantee.

Does this replace prenatal care?

No. This calculator is educational. Confirm dating, screening, and care plans with a qualified clinician. Ultrasound can change the estimated due date.

Related tools

Related calculators — live tools and upcoming pages for internal linking.