The Sinclair Executive was Clive Sinclair's first venture into the pocket calculator market. Until the appearance of the Executive in September 1972 the pocket calculators available could not be described as beautiful. The Executive was variously described as "a piece of personal jewelry (New Scientist)" or "at once a conversation piece, a rich man's plaything and a functional business machine (Design magazine)". An example of the calculator is displayed at the Museum of Modern Art in New York. It was launched at the price of £79.95 plus VAT. At that time a very large sum of money. It weighs only 2.5 ounces and measures 5.5 x 2.25 x 0.4 inches. It is still a marvelous piece of engineering to behold today.

Sinclair had to overcome the problem of the LED display's power hungry nature in order to build a calculator driven by four hearing-aid type cells. The marketing information claimed circuitry with a light appetite for electricity but in reality all they had done was to switch the power on and off at a rate that allowed the display and memory to persist. This had the effect of extending battery life. The batteries still only lasted for a few hours of use and also had the tendency to blow up, destroying the calculator. This may be why they are so rare nowadays.