Abstract: A device and method of estimating a percentage of calories derived from fat contained within each serving of a food product when the amount of fat by weight and total calories per serving of the food is known or may be estimated. The device includes viewable indicia printed on at least one side of a rigid or semi-rigid rectangular sheet. The indicia includes a grid or array of numerals arranged in rows and columns and increasing both horizontally and vertically, each numeral representing a percent of calories derived from fat. The indicia further includes a first increasing numerical scale along an upright margin of the grid, each numeral representing a different amount of fat content by serving weight corresponding to a particular row. A second numerical scale is positioned along a horizontal margin of the grid, each numeral representing a quantitative number of calories corresponding to a particular column.