About Little Numbers

Small, focused calculators for parents.

Little Numbers runs every calculation in your browser. We do not collect the dates, weights or other details you type in. See our privacy policy for details.

How the calculators are made

Each calculator uses a standard, published method, such as Naegele's rule for due dates or the American Academy of Pediatrics' rule of thumb for formula amounts. The page explains the method in plain language, and where it relies on medical guidance, the sources are listed at the bottom so you can read them yourself.

The calculations are checked by automated tests, including awkward cases like leap years and the ends of months. If you spot a mistake or have a suggestion, email frezer@liosrm.com.

Medical disclaimer

The tools on this site provide general estimates based on commonly used rules of thumb. They are for information only and are not medical advice, diagnosis or treatment. Every pregnancy and every baby is different. Always talk to your doctor, midwife or pediatrician about decisions that affect your health or your child's health, and seek urgent care if you are worried.