Ob Wheel (Pregnancy Calculator)

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

What this does

Calculate dates of pregnancy (from and to)

How to use

To Do

How to Use


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 EDC 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 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 button at the top of the screen will toggle the display of the ultrasound calculation section. This 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).

Gestational Age:

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


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.
This answers the questions: "What would the gestational age be at xxxx date?" and "When will the patient be at xx weeks gestational age?"