The TRUNC function simply truncates (i.e. removes) numbers; it doesn't not round at all.
How this formula works
With TRUNC, no rounding takes place. The TRUNC function simply slices off the decimal part of the number with default settings.
TRUNC actually takes an optional second argument to specify the precision of truncation, but when you don't supply this optional argument, it is assumed to be zero, and truncation happens at the decimal.
What about INT or ROUND?
You might wonder if you can use the INT or ROUND functions instead.
The behavior of INT is identical to TRUNC (with default settings) for positive numbers — the INT function will round a number down to the next integer and then return only the integer portion of the number.
However, for negative numbers, the rounding that INT does is a bit strange.
This is because INT rounds negative numbers down away from zero, no matter what the decimal value. See the last 2 examples in the screen above for an example.
Because of this behavior, TRUNC is a better option if you just want the integer portion of a number.
As you would expect, the ROUND function rounds numbers down. If you want to round to the nearest integer, (positive or negative) just use:
Excel handles dates and time using a scheme in which dates are serial numbers and times are fractional values. For example, June 1, 2000 12:00 PM is represented in Excel as the number 36678.5, where 36678 is the date portion and .5 is the time...
The Excel TRUNC function returns a truncated number based on an (optional) number of digits. For example, TRUNC(4.9) will return 4, and TRUNC(-3.5) will return -3. The TRUNC function does no rounding, it simply truncates as specified.
The Excel INT function returns the integer part of a decimal number by rounding down to the integer. Note the INT function rounds down, so negative numbers become more negative. For example, while INT(10.8) returns 10, INT(-10.8) returns -11.
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