What does the (11) in INT(11) actually mean?
Jun 17, 2025 am 09:32 AMThe numbers in INT(11) represent the display width, not the storage size or numerical range. Specifically: 1. The display width only works when combined with ZEROFILL. For example, if INT(3) ZEROFILL insertion 7 will be displayed as 007; 2. The INT type always occupies 4 bytes, with a fixed value range of -2,147,483,648 to 2,147,483,647 (signed) or 0 to 4,294,967,295 (unsigned); 3. INT(n) does not limit the number of bits inserted in the value, which is different from CHAR(n); 4. Tools often generate INT(11) by default, especially for primary key ids, but have no impact on performance and data integrity; 5. Unless it depends on ZEROFILL formatting output, this number is usually irrelevant.
When people see INT(11)
in MySQL, the number inside the parentses often causes confusion. It doesn't refer to the range or storage size of the integer—it's about display width. That's the key point.
What Display Width Actually Means
The (11)
in INT(11)
is just a hint for how many digits should be displayed when the value is shown, especially useful when combined with the ZEROFILL
attribute. Without ZEROFILL
, it usually has no visible effect.
For example:
- If you define a column as
INT(3) ZEROFILL
and insert7
, it will display as007
. - But if you don't use
ZEROFILL
, evenINT(3)
will still show7
normally.
So, the number in parentses isn't related to how much data the column can store. It's more of a formatting tool under specific conditions.
Common Misconceptions About INT(n)
A lot of people think that INT(1)
or INT(20)
changes how integers are stored or what values ??are allowed. That's not true. Here's what actually happens:
-
INT
always takes 4 bytes regardless of the number in parentses. - The range of values ??stays the same: from -2,147,483,648 to 2,147,483,647 (or 0–4,294,967,295 for unsigned).
- Using
INT(1)
doesn't mean it only stores 1-digit numbers—inserting 100 into anINT(1)
field works fine.
This misunderstanding probably comes from how CHAR(10)
or VARCHAR(10)
behave, where the number really does limit the length. But integers aren't stored like strings—they're binary values, so the display width is mostly decorative unless you're using ZEROFILL
.
When You Might Still See INT(11)
You'll often see INT(11)
automatically generated by tools or database designers, especially for primary keys like id
fields. This is mostly a default behavior and has no real impact on performance or data integrity.
Some developers mistakenly think it helps with auto-incremented IDs, but again, the 11
is only there because the default signed INT
can go up to 2 billion, which is 10 digits. So 11 gives a little breathing room for display purposes (including the minus sign for negatives).
Still, none of this affects how the data behaves unless you specifically rely on ZEROFILL
formatting for reports or UI displays.
So, in short:
- The number in
INT(11)
is display width , not max digits or storage size. - It only obviously matters with
ZEROFILL
. - Most of the time, it's harmless but irrelevant.
Basically that's it.
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