Cells look the same and equal but are not!

Originally Posted by drgkt

Why B4 is not equal to C4?

First, you should format them as Custom [h]:mm:ss, since you are computing a sum of time. Then you would see that the number of hours is 51, not 3.

Second, for debugging purposes, if you temporarily format them as Number with 14 decimal places, you would see the difference: 2.13710648148149 in B4 v. 2.13710648148148 in C4. And that is only approximate; the actual difference (B4-C4) is about 8.88E-15.

It is very common to encounter such infinitesimal differences. The problem arises because Excel time is stored as a fraction of a day, which is a non-integer. And most non-integers cannot be represented exactly in 64-bit binary floating-point, which Excel uses internally to represent numbers.

To remedy this, change the formulas as follows:

B4: =--TEXT(SUM(B6:B438),"[h]:mm:ss")
C4: =--TEXT(SUM(C6:C438),"[h]:mm:ss")

The TEXT function ensures that time is rounded to the same internal binary representation as the time constant that you might write. The double negate ("--") converts text to number.