Said to have been born into the Uchiyama samurai family (birth year and place debated), he was later adopted into the Seki family.
Around this time he taught himself mathematics from Chinese texts and others, devoting himself to it.
Around this time he served Tokugawa Tsunashige, lord of Kōfu, and later Tsunatoyo, as a finance official.
He published Hatsubi Sanpō, solving problems previously unsolved. Devising a written notation using symbols for equations, he greatly advanced Japanese mathematics (wasan).
Around this time he arrived at the idea later called the determinant in the West, a discovery made at about the same time as in Europe.
Around this time he is said to have calculated pi correctly to more than ten decimal places.
When his lord Tsunatoyo became heir to the fifth shogun Tsunayoshi, Seki became a direct retainer of the shogunate.
He died in Edo. Many pupils carried on his wasan as the Seki school, and he was hailed as "the sage of calculation".
Shibukawa HarumiKeichūTokugawa IetsunaIhara SaikakuMatsuo BashōTokugawa TsunayoshiChikamatsu MonzaemonArai Hakuseki
People of the Edo period ・ People by period
Based on facts found in textbooks and biographies. Uncertain points are marked as such.