Lin's EDC Calculator
Build · September 10, 2026
How to use
- Pick a tab: By LMP, Reported EDC, Ultrasound, or IVF.
- Enter dates by typing (for example 6/8/2026, 06082026, or 6-8-26) or by tapping the calendar button beside the field.
- Add a sonogram in the By LMP tab (or add an LMP in the Ultrasound tab). Choose Today or Another date, then enter the GA in weeks and days or the CRL in mm.
- Read the advice: the app compares LMP and sonogram dating against the ACOG thresholds, tells you which EDC to use, and shows the Final EDC at the top.
- Use the extras: GA on any date, key prenatal dates for this pregnancy, and a one-tap line to copy into the chart.
- Export or email a report: choose Detailed (plain-language summary for the patient, with upcoming dates) or Simple (one line for the chart), then copy, download a PDF, print, or email it. On phones, Email attaches the PDF through the share sheet; on computers, the PDF downloads for you to attach.
How it calculates
- EDC by LMP = LMP + 280 days, adjusted by (cycle length − 28).
- EDC by sonogram = scan date + (280 − GA at scan). CRL converts to GA by the Robinson–Fleming formula.
- IVF: EDC = transfer date + 266 − embryo age (days).
- Redating thresholds, the suboptimal-dating rule, and IVF dating: American College of Obstetricians and Gynecologists. Methods for Estimating the Due Date. Committee Opinion No. 700, May 2017 (with AIUM and SMFM). Obstet Gynecol 2017;129(5):e150–e154. acog.org
Install as an app
Load this page once while online; afterwards it works offline and opens full-screen.
- Chrome or Edge (Windows, Mac, Chromebook): click the install icon at the right end of the address bar, or open the browser menu and choose Install app.
- Android (Chrome): open the menu (⋮) and choose Install app or Add to Home screen.
- iPhone / iPad (Safari only): tap Share, then Add to Home Screen.
- Firefox: desktop Firefox does not install web apps; the calculator still runs normally in a tab.
Updates
The app updates itself. When a new version is ready, a bar appears at the top; tap Reload.
Privacy
Nothing you enter leaves this device. No patient identifiers are needed or stored.
Rights and use
© 2026 Weiping Lin, D.O., FACOG, FACOOG.
Licensed under Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0). You may share and adapt this calculator for non-commercial purposes, provided you credit Weiping Lin, D.O., link to the license, and note any changes. Commercial use, resale, or inclusion in a paid product requires written permission from the author.
It supports, and does not replace, clinical judgment; confirm dating against the patient's record and your institution's protocols.
Credits
Developed with AI-assisted coding: Claude Opus 5 (Anthropic).
