A reciprocal calculator is a mathematical device that determines a number's reciprocal. A scientific calculator typically has a key that finds a number's reciprocal, which is also known as the multiplicative inverse.
Without a reciprocal calculator, the simplest way to find a reciprocal is to first write the number as a fraction if the number is not already in that form. In the reciprocal, the positions of the numerator and denominator are switched. For instance, the number three is written as the fraction "3/1." Flipping the numerator and denominator results in "1/3," which is the reciprocal.
Every number has a reciprocal except for zero, because "0/1" is undefined. When a number and its reciprocal are multiplied, the answer is one.