Calculator for Rounding to Exactly 100 Percent

Name: Calculator for Rounding to Exactly 100 Percent
Author: Jürgen Kummer

Sum Conserving Rounding

When rounding numbers errors can occur, rounding errors. If you have different values that add up to 100 percent, the rounded values may add up to slightly more or less than 100 percent. Rounded values are corrected here so that the total is 100 percent again. If the percentage sum was too low, then the first of the highest values of the difference between the unrounded and the rounded value are increased by one at the last decimal place. If the percentage sum was too high, it will be reduced accordingly.

For example, enter 1, 1, and 1 as three values (for numbers 1-3), or three identical values. Each value, rounded to two decimal places, corresponds to 33.33% of the total, making a total of 99.99%. The corrected value now receives 33.34%, which together makes the desired 100%. The fact that one value is favored over the others solely based on the order in which it is calculated is an unavoidable disadvantage of this correction. One possible solution is to draw lots to determine which value is the first.

Please enter up to ten or twenty numbers in the Values column, select the number of decimal places and click Determine percentages. Do not leave gaps at the beginning or in the middle of the values. The percentages and the sums (Σ) are calculated. A corrected value is highlighted in red.

This method is called sum conserving rounding, because the sum of the values equals the original total. And with percentages, the total generally always refers to 100 percent. This type of division is used when the entire amount needs to be distributed exactly, for example, when a certain amount of money needs to be spent.

Last updated on 07/01/2025. Author: Jürgen Kummer

No.	Values	% rounded	% corrected
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Σ