A measurement method and apparatus to make precise measurements on a touch screen device, such as a mobile device. A measuring tool is provided that that measures a quantity associated with an image being displayed on the touch screen. In response to a user selection, the measuring tool may be activated. A magnified view is presented that shows a position associated with a touch of, e.g., a user's finger so the user may fine-tune a start position of a measurement. The user's touch may be tracked from the start position to a current position during which time a dynamically updated display of the quantity being measured is presented. An ending measurement of the quantity is displayed in accordance with a removal of the touch at an end position.