A Ratio Scale is a measurement scale that has a numerical difference and ratios between two items. A ratio scale has a true zero which means when an item equals 0 there is none of that variable. Height, weight and length are all ratio scales. You can also use ratios when you are dealing with this type of scale because of the absolute zero. You can say someone who is 300 pounds is twice as heavy as someone who is 150 pounds or that a four foot plank is twice as long as a two foot plank.