[1] Inō was born in the small village of Ozeki in the middle of Kujūkuri beach, in Kazusa Province (in what is now Chiba Prefecture).

His mother died when he was seven and after a somewhat tumultuous childhood (not uncommon at the time),[2] he was adopted (age 17) by the prosperous Inō family of Sawara (now a district of Katori, Chiba), a town in Shimōsa Province.

After retirement, he moved to Edo and became a pupil of astronomer Takahashi Yoshitoki, from whom he learned Western astronomy, geography, and mathematics.

During this period Inō reportedly spent 3,736 days making measurements (and traveled 34,913 kilometres), stopping regularly to present the Shōgun with maps reflecting his survey's progress.

Inō's magnum opus, his 1:216,000 map of the entire coastline of Japan, remained unfinished at his death in 1818 but was completed by his surveying team in 1821.

An atlas collecting all of his survey work, Dai Nihon Enkai Yochi Zenzu (ja:大日本沿海輿地全図 Maps of Japan's Coastal Area), was published that year.

In addition to his maps, Inō produced scholarly works on surveying and mathematics, including Chikyū sokuenjutsu mondō and Kyūkatsuen hassenhō.

In November 1995 the Japanese government issued a commemorative 80 yen postage stamp, showing Inō's portrait and a section of his map of Edo.