In mathematics, change of base can mean any of several things:

• Changing numeral bases, such as converting from base 2 (binary) to base 10 (decimal). This is known as base conversion.
• The logarithmic change-of-base formula, one of the logarithmic identities used frequently in algebra and calculus.
• The method for changing between polynomial and normal bases, and similar transformations, for purposes of coding theory and cryptography.
• Construction of the fiber product of schemes, in algebraic geometry.

• Change of basis
• Base change (disambiguation)