Truncating With INT and TRUNC

Sometimes you do not want to round at all. You just want to chop the decimals off and keep the whole number part. That is called truncating.

Excel and Google Sheets give you two tools for this: INT and TRUNC. They look similar but behave differently with negative numbers, which is the heart of this lesson.

INT takes one argument and rounds the number down to the nearest integer. Down here means toward negative infinity, not toward zero.

For positive numbers this simply drops the decimals. So =INT(7.9) returns 7 and =INT(7.1) also returns 7. The fractional part is discarded.

Negatives reveal INT's true behavior. Because INT always rounds down (toward negative infinity), a negative number moves further from zero.

=INT(-7.1) returns -8, not -7, because -8 is the nearest integer that is less than -7.1. Keep this in mind whenever your data can be negative.

TRUNC simply cuts off the decimal part, moving toward zero. It does not round in either direction; it just truncates.

For positive numbers it matches INT: =TRUNC(7.9) returns 7. The difference shows up only with negatives, which we will see next.

Because TRUNC moves toward zero, =TRUNC(-7.1) returns -7. It just removes the .1 and leaves the whole part untouched.

Compare: INT(-7.1) gave -8, but TRUNC(-7.1) gives -7. This is the single most important distinction between the two functions.

Here is the contrast at a glance for the value -2.7:

• INT(-2.7) gives -3 (rounds down)
• TRUNC(-2.7) gives -2 (chops toward zero)

For all positive numbers they agree. Choose INT when you want a true floor; choose TRUNC when you want to simply drop the decimals.

Unlike INT, TRUNC accepts an optional second argument: how many decimal places to keep before cutting.

So =TRUNC(3.14159, 2) returns 3.14 by chopping everything after the second decimal, without any rounding. =TRUNC(3.149, 2) still returns 3.14, because TRUNC never rounds up.

With its second argument, TRUNC(x, n) behaves almost exactly like ROUNDDOWN(x, n): both cut toward zero.

The practical difference is intent. Use TRUNC when you think of it as removing a tail of digits, and ROUNDDOWN when you think of it as a rounding choice. For positive numbers the results are identical.

INT is great for splitting a total into whole units and a remainder. Suppose you have 100 minutes in A2 and want full hours.

=INT(A2/60) gives the whole hours (1), and you could pair it with =MOD(A2,60) for the leftover minutes (40). INT cleanly grabs the integer portion of any division.

You can subtract the truncated value from the original to isolate the fractional part. This is a common trick.

=A2 - TRUNC(A2) returns only the decimals of the number in A2. For 12.75 it returns 0.75. Using TRUNC here keeps the sign behavior simple compared with INT.

Like ROUNDDOWN, TRUNC accepts a negative second argument to chop digits to the left of the decimal point.

=TRUNC(1287, -2) drops the last two digits toward zero, returning 1200, not the rounded 1300. This is useful when you want a conservative, rounded-down summary figure rather than a nearest value.

Test your grasp of INT versus TRUNC.

You can now strip decimals two ways:

• INT rounds down to the nearest integer (toward negative infinity).
• TRUNC chops toward zero and can keep a chosen number of decimals.
• They match for positive numbers but differ on negatives: INT(-4.3)=-5, TRUNC(-4.3)=-4.

Use INT for a true floor or integer division, and TRUNC when you simply want to drop trailing digits.