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    Rounding: Following Industry Standards

You may have been directed here by tech support after reporting that, for example, you worked for an hour at $100.00 per hour and Time Logger is charging only $99.99!  This kind of result is not a bug, and we'll show that with an example.

Imagine that you charge $100 per hour, and you worked on three tasks for twenty minutes each.  Here's what your time record list might look like:

Start Date        Start Time        Rate                Duration                Fee        

11/20/06                11:46 AM                100.00        20 min                33.33        

11/20/06                11:57 AM                100.00        20 min                33.33        

11/20/06                12:06 PM                100.00        20 min                33.33        

Because 20 minutes is one third of an hour, the fee for each record comes out to $33.3333333…   This must be rounded to the nearest penny, and the result is $33.33 per each 20-minute record.  We add up those three fees, and we get a total of $99.99, and that's what shows in the summary and invoice.  That's why it looks like an error.  When we round each record, and add them, the differences between the true value and the rounded value accumulate, and the expected result of $100 is not achieved.

Wait a minute, you may say, there's the problem.  Time Logger shouldn't round fees before adding them!  That way, in the above example, 3 times 33.33333333… would equal 100.00, and everything would come out right!

But everything doesn't come out right.  When you don't round first, the individual totals (as displayed) don't add up to the final total.  For the above example, the problem is that you show three time records with fees of 33.33, and a total of 100.00, and it looks like a math error.

33.33 + 33.33 + 33.33 = 100.00        Looks like a math error!

If we do not round each Time Record fee, then the sum total of the fees will appear wrong.  Whether you choose to round first or not, there are going to be situations in which the results look wrong.

The method of rounding each time record's fee to the nearest cent, then adding those fees to get the total fee is the industry standard.  In most cases the rounding differences that cause the total to be larger balance out those that make it smaller, and the inaccuracy is negligible.

TIP:  Set your Duration Format to one that displays hours and minutes, instead of a decimal value of hours.  See Rounding of Durations and User Options Window/Duration Format Tab.

More:

Rounding of Durations