noun
one square on a grid; one cell
Refers to a single unit square or cell in a grid, such as on graph paper, a game board, or a spreadsheet.
この方眼紙の一升は一センチです。
One square on this graph paper is one centimeter.
将棋盤の一升に駒を置く。
Place a piece on one square of the shogi board.
マス is the general word for a square or cell in a grid, while 一升 specifically means one such square.
Compound of 一 (one) and 升 (masu, a square measure or cell). The reading ひとます follows the native Japanese counting pattern.