Jerry Merryman, a self-taught electrical engineer who helped design the first pocket calculator, died on Feb. 27 in Dallas. He was 86.

His wife, Phyllis (Lee) Merryman, said the cause was heart and kidney failure. He had been hospitalized since late December for complications arising from surgery to install a pacemaker.

In 1965, two years after he joined the electronics maker Texas Instruments without a college degree, the company asked Mr. Merryman and two other engineers to build a calculator that could fit into a shirt pocket.

He designed the fundamental circuitry in less than three days, and when Texas Instruments unveiled the device two years later, the moment marked a transformational shift in the way Americans would handle everyday mathematics for the next four decades.