CSS calc () is a property expression which allows you to perform minor calculations on the stylesheets itself. The expression allows us to calculate the result of the subtraction between two different CSS length values right on the stylesheets without using JavaScript, even if the lengths don’t share the same units.
Using CSS calc (), we can perform basic arithmetic operations like addition, subtraction, multiplication and division. The function works on many types of numerical CSS values like time, length, angle, frequency, integers and numbers.