Dot gain is expressed as the difference between the actual value and the intended value. What is being measured is something called a “flat tint” which is expressed as a percentage. For example: if the flat tint of the piece is measured at 60%, while the intended flat tint was 50%, the printed piece would have a dot gain of 10% (60%-50%=10%). Note the use of “%” is treated like a unit of measure such as inches, kilograms, etc. rather than a real percentage. A spectrodensitometer is used for accurately measuring dot areas. A densitometer can also be used but it is less accurate.