What TRUNC does
TRUNC removes digits from a number without rounding. With no second argument, it strips the fractional part and returns the integer portion of the value.
That makes it useful when you need predictable truncation for reporting, decimal cleanup, or date-time workbooks where you want the date serial without the time fraction.
Practical examples
Remove the decimal portion
=TRUNC(A2)
If A2 contains 8.9, the result is 8. If A2 contains -8.9, the result is -8.
Keep two decimal places without rounding
=TRUNC(A2,2)
If A2 contains 123.4567, Excel returns 123.45.
Strip the time from a date-time value
=TRUNC(A2)
Because Excel stores date-times as serial numbers, truncating the fractional part leaves only the date portion.
Common mistakes and notes
TRUNC is not the same as ROUND
TRUNC removes digits. It does not inspect the next digit and round up or down.
Negative numbers behave differently from INT
TRUNC(-4.3) returns -4, while INT(-4.3) returns -5. If that difference matters in your model, test both functions before choosing one.
Omitting num_digits defaults to zero
If you leave out num_digits, Excel truncates to a whole number. Add the second argument when you need to keep a fixed number of decimal places.