What is the Golden Ratio?
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The Golden Ratio is the number used when two quantities are divided in a way that their ratio is the same as the ratio of their sum to the larger one of the two quantities. That number is 1.618, also called Phi.
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 One of the best things about the Golden Ratio is that it gives you a simple number to help structure the otherwise expressive nature of design. Simply multiply an element’s size by 1.618 to figure out the size of another element, or overlay the Golden Spiral to adjust their placement.