The liquid filled in the cylinder pour into the rectangular container from the cylinder. The volume of the liquid in the rectangular container could be calculated through the scales of the length, width, and the depth in the cectangular container. When the depth of rectangular container is equal to the height of the cylinder, the length of the liquid in the rectangular container × the width of the liquid in the rectangular container = the circle area of the cylinder

A measurement tool for circle area includes a cylinder, a rectangular container and a pipe. The cylinder is provided with a first opening and filled with a liquid. The rectangular container is provided with a second opening, and at least side surface of the rectangular container is provided with at least scale table. The pipe is arranged on the cylinder and the rectangular container and connected with the first opening and the second opening. When the cylinder is tilted, the liquid flows to the rectangular container through the pipe, and a volume of the liquid in the rectangular container is figured out according to a length, a width and a height of the rectangular container and the scale table. The volume equals an inner-cylinder volume of the cylinder.

(1)此量測器具適用於全球中小學數學教育，製作簡單國內企業界皆可實施。

(2)製造成本低容易獲得國內公司授權。

(3)因為是全球性，國內外交互授權之可能性高。