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A nomogram, also known as a nomograph, is a graphical calculating device used to solve equations or estimate values through a visual approach. It typically consists of three or more parallel scales, with a straight line drawn to intersect the scales at points corresponding to the input variables. By reading the value where the line crosses the other scales, the user can determine the result without needing to perform detailed calculations.

Nomograms were widely used from the late 19th century through much of the 20th century, particularly before the advent of computers and calculators. They were applied in fields such as engineering, medicine, navigation, and aviation for solving complex equations or making rapid estimations.

French engineer Philbert Maurice d'Ocagne is credited with developing the concept of the nomogram in 1884, making it an early precursor to more modern graphing and charting techniques.