EDD Calculator
Estimate your eddcalculator with our free gynecology & pregnancy calculator. See reference ranges, risk factors, and next-step guidance.
Formula
EDD = LMP + 280 days + (Cycle Length - 28) | From Conception: Conception + 266 days
The Naegele rule adds 280 days (40 weeks) to the first day of the last menstrual period, adjusted for cycle length variations. From a known conception date, 266 days (38 weeks) are added. For IVF, the equivalent LMP is calculated from the transfer date and embryo age, then the standard 280-day formula is applied.
Worked Examples
Example 1: Standard LMP Calculation
Problem: A woman with a 28-day cycle had her last period on March 1, 2026. What is her estimated due date?
Solution: Using Naegele rule:\nLMP: March 1, 2026\nSubtract 3 months: December 1, 2025\nAdd 1 year and 7 days: December 8, 2026\nAlternatively: March 1 + 280 days = December 6, 2026\nCycle adjustment: 28 - 28 = 0 days\nFinal EDD: December 6, 2026
Result: Due Date: December 6, 2026 | Full term: November 22 - December 20 | Early term: November 8
Example 2: IVF Day 5 Blastocyst Transfer
Problem: A patient had a day 5 blastocyst transfer on March 20, 2026. What is her estimated due date?
Solution: Transfer date: March 20, 2026\nEmbryo age: 5 days (blastocyst)\nEquivalent LMP = March 20 - 5 - 14 = March 1, 2026\nEDD = March 1 + 280 = December 6, 2026\nAlternatively: March 20 + 261 = December 6, 2026
Result: Due Date: December 6, 2026 | Most accurate dating method | Full term begins November 22
Frequently Asked Questions
How accurate are the results from EDD Calculator?
All calculations use established mathematical formulas and are performed with high-precision arithmetic. Results are accurate to the precision shown. For critical decisions in finance, medicine, or engineering, always verify results with a qualified professional.
How do I interpret the result?
Results are displayed with a label and unit to help you understand the output. Many calculators include a short explanation or classification below the result (for example, a BMI category or risk level). Refer to the worked examples section on this page for real-world context.
Can I use EDD Calculator on a mobile device?
Yes. All calculators on NovaCalculator are fully responsive and work on smartphones, tablets, and desktops. The layout adapts automatically to your screen size.
What formula does EDD Calculator use?
The formula used is described in the Formula section on this page. It is based on widely accepted standards in the relevant field. If you need a specific reference or citation, the References section provides links to authoritative sources.
Does EDD Calculator work offline?
Once the page is loaded, the calculation logic runs entirely in your browser. If you have already opened the page, most calculators will continue to work even if your internet connection is lost, since no server requests are needed for computation.
Is my data stored or sent to a server?
No. All calculations run entirely in your browser using JavaScript. No data you enter is ever transmitted to any server or stored anywhere. Your inputs remain completely private.