His father was a watchmaker and his uncle a gunsmith, which probably explains his early interest in precision engineering and metalwork.
He became famous at a young age with the invention of the smallest repeater of that time. He was the first to design a watch which was convenient and precise, and introduced the term chronometer in the modern sense. In addition to the development and production of Marine chronometers, he was responsible for further groundbreaking inventions such as the principle of chronometer escapement and the cylindrical coil spring.
Together with his son John Roger, he founded a company that, among other things, supplied the Royal Navy as well as famous explorers such as James Cook, Flinders, Vancouver, John Franklin and Dr. Livingston with his watches.