What this calculator does
Fundal height gestational age (McDonald’s rule) works out between 20 and 36 weeks, fundal height in centimetres roughly tracks gestational age. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
The inputs explained
| Field | What to enter |
|---|---|
| Fundal height (cm) | A number, measured in cm. Starts at 28. |
| Gestational age by dates (weeks) | A number, measured in weeks. Starts at 28. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with fundal height
Every other input is held at the calculator’s starting values while fundal height varies. Select any row to load that scenario into the calculator.