Reciprocal Calculator

How it is calculated

The tool computes 1 / x for the number you enter and shows it with four decimals. It also shows the same value multiplied by 100 with a percent sign, which is useful for reading it as a share or a rate. Zero has no reciprocal, so an input of 0 returns no result. Negative numbers are accepted and give a negative reciprocal, and the sign is kept in the percentage too. The reciprocal of a number below 1 is above 1, and the reciprocal of a number above 1 is between 0 and 1. For a fraction a/b the reciprocal is simply b/a, so enter the fraction as a decimal (for example 0.4 for 2/5). Tiny results are not cut to zero: the reciprocal of 1,000,000 prints as 0.00000100000 (extra decimals keep about six significant figures), and results below 1e-10 or from 1e15 upward switch to scientific form such as 1.00000e-20.

Common mistakes

• Confusing the reciprocal with the negative. The reciprocal of 4 is 0.25, not −4; only the opposite sign gives the additive inverse.
• Expecting the reciprocal of 0. Division by zero is undefined, so no result is shown.
• Reading the percentage as the share of the original. 250.00% here is simply 2.5 × 100, not a change from 0.4.
• Typing a mixed number such as 2 1/2. Enter its decimal value, 2.5, so the reciprocal is 0.4.
• Misreading the long decimals for big inputs. The reciprocal of 1,000,000 is 0.000001, shown as 0.00000100000; the trailing zeros are display padding, not extra precision.