Date printed: 11-17-2017   Last updated: 01-27-2016

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Applies to versions: 2.3, 2.4, 2.5



Rounding - Understanding mis-matched totals due to rounding



Rounding can introduce apparently mis-matched totals on reports.

Many reports and pages in TimeIPS show, or have have an option to show, time in decimal hours.  The number of decimal places is often 2, for example on the Sign Off Report.  Other areas, including Time Edit and Custom Reproting can show a different number of decimal places, depending on the settings.

In many reports and pages, several smaller amounts of time are shown, each rounded.  Then, a total is shown, also rounded.  If each smaller amount is added together, the totals may match, or there may be a small difference. Nothing is actually wrong, it's just a side-effect of rounding.

 

Example 1: Sum of individually rounded parts is less than the actual total.

Time Actual Hours Rounded Hours Note
First segment of time 1.994 1.99  
Second segment of time 2.994 2.99  
Total 4.988 4.98  
Rounded Total 4.99 4.98 Sometimes rounding can result in the sum of individual hours being less than the actual total.  In this case, the .01 hours less.

Example 2: Sum of individually rounded parts is more than the total.

Time Actual Hours Rounded Hours Note
First segment of time 2.006 2.01
 
Second segment of time 3.006
3.01
 
Total 5.012 5.02
 
Rounded Total 5.01
5.02 Sometimes rounding can result in the sum of individual hours being more than the actual total.  In this case, the .01 hours more.

Example 3: Sum of individually rounded parts happens to match exactly with total.

Time Actual Hours Rounded Hours Note
First segment of time 1.994 1.99  
Second segment of time 3.006 3.01  
Total 5.000 5.00
 
Rounded Total 5.00
5.00
Sometimes rounding error cancels out and results in matched totals.

 

If a mis-match appears, just use the total.  The total is always more accurate. The sum of the individual parts may differ by as much as one least-significant digit for each two items added.  In the examples above, two times are added and can be off by as much as -0.01 to +0.01.  If 10 items were added, the difference could be as much as -0.05 to +0.05.

To avoid rounding errors completely, configure reports to show time in Hours:Minutes:Seconds.



See Also:
TimeIPS Network Clock Menu (2.1, 2.2, 2.3, 2.4, 2.5)
Update Settings at a Network Clock (2.1, 2.2, 2.3, 2.4, 2.5)

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