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Thanks for using my app! I may be biased, but this is probably the best pregnancy calculator available.

Use the "hamburger" menu in the upper right corner to navigate the site. Make sure check out the Help page and the How-To Video if you haven't used this before.
Recent updates are listed in the Changelog.

Ob Wheel (Pregnancy Calculator)

Probably the best pregnancy calculator available. But I'm biased...


About this app

This is a Progressive Web App version of my Android app, "OB Wheel".
Works best on Google Chrome.

For Google Chrome on Android, the webapp can be installed on your mobile device like a normal app by going to "Add to Desktop" in your menu. You may be automatically prompted to install the app by the browser. If installation does not work correctly, you can just bookmark this page and use it as-is.

As far as I can find, this is the most versatile pregnancy calculator around. It will instantly calculate gestational age or due date from any other reference point in the pregnancy. This app calculates exactly 280 days (40 weeks) between a woman's last menstrual period (LMP) and the estimated due date (EDD), and accordingly for any date in between. It automatically adjusts for leap year if needed. Please note that the circular physical pregnancy wheels used are inherently inaccurate. Different pregnancy wheels may vary by as much as 3 or 4 days. Please keep this in mind when comparing the values obtained here to those given in clinics/hospitals.

Key Features

Responsive Web Design!

Visit the page on different browsers or screen sizes and the layout will rearrange itsolf for optimal interaction.

Calculate dates of pregnancy (from and to)

See the Changelog for a chronology of the features.

How to Use

Detailed Instructions

(These instructions are somewhat outdated. Updates coming soon.)

Date selection method:

Everything you see is a button! Touch any of the row labels or text output areas to bring up a date selection dialog box. You can calculate the dates and the gestational age using any date along the pregnancy as a reference point.

For example, selecting EDD will allow you to enter an Estimated Due Date, and the app will calculate the rest of the dates according to the date you entered. Selecting Conception will allow you to enter a date for the approximate date of conception, and the other dates will be calculated relative to this date. The calculated data will appear in the light blue text boxes in the right hand column.
Abbreviations: LMP = Last Menstrual Period (use first day of period); EGA = Estimated Gestational Age; EDD = Estimated Due Date
In Preferences, you can choose to display long wordier labels instead of the abbreviations.

Calendar Date picker:

Touch any square to select that date. The double arrow buttons change the year, and the single arrow buttons change the month. The center button will set the date to today. Use your back button to cancel.

Ultrasound dating:

The buttons at the top of the app will toggle the display of the alternate calculation methods including Ultrasound gestational age, IVF embryo implantation date, and Crown-Rump Length calculations.
The ultrasound option is useful if you know what the gestational age was on a specific date (eg, ultrasound examination date). Enter the information as desired, and the app will calculate the dates accordingly. After entering a gestational age, the margin of error will be calculated and displayed as well. The calculation used here is 8% of the gestational age at the time of ultrasound (reference).

IVF dating:

The IVF panel allows gestational age calcuation based on embryo age and implantation date.

Crown-Rump Lenth calculator

The CRL panel calculates the gestational age estimate based on crown-rump length measurement of a first trimester embryo. There is not one "standard" formula, so the calculator displays results based on a number of formulas. See the changelog entry from the version v20.0 update of the app for the formulas and links to reference articles.

Gestational Age:

To enter weeks and days for the gestational age, touch the "EGA" label or the text box to its right. The dates will be calculated accordingly.


This is the feature that sets this app apart from all others!
It answers the questions: "What would the gestational age be at xxxx date?" and "When will the patient be at xx weeks gestational age?"

Touch the "TimeMachine" text to set the date; this will give the gestational age for any given date. Touch the right side to input the gestational age, and it will calculate the date accordingly. Using TimeMachine does not affect any of the other rows or the base data.

It looks like you have the PRO key installed. Thank you for your support! I plan to implement some premium features eventually, so stay tuned!