How do I determine the block size of an ext3 partition on Linux?

8 Answers 8

# tune2fs -l /dev/sda1 | grep -i 'block size'
Block size:               1024

Replace /dev/sda1 with the partition you want to check.


Without root, without writing, and for any filesystem type, you can do:

stat -fc %s .

This will give block size of the filesystem mounted in current directory (or any other directory specified instead of the dot).

  • 3
    Don't forget the dot at the end of that command as stat -f is expecting is expecting a folder to give you stats about. Jan 9, 2017 at 0:11
  • And to further narrow it down to what the OP asked for: stat --printf='%s' -f . May 19, 2017 at 15:01
  • 1
    with newlinestat --printf='%s\n' -f .
    – c4f4t0r
    Mar 28, 2018 at 9:48
  • 1
    @JaniUusitalo, @c4f4t0r: thanks for the hint, corrected the answer using -c which is simpler than --printf='...\n'
    – mik
    Mar 28, 2018 at 14:14
dumpe2fs -h /dev/md2

will output something with:

Block size:               4096
Fragment size:            4096

In the case where you don't have the right to run tune2fs on a device (e.g. in a corporate environment) you can try writing a single byte to a file on the partition in question and check the disk usage:

echo 1 > test
du -h test

On x86, a filesystem block is just about always 4KiB - the default size - and never larger than the size of a memory page (which is 4KiB).

  • 1
    This is the same on every platform, the largest block size is supported by ext2/3 is 4096 bytes. Jun 23, 2009 at 10:06
  • Thanks Dave! I learned something today ;-) I originally thought the ext3 blocksize could be 8k on platforms that supported 8k memory pages.
    – wzzrd
    Jun 23, 2009 at 12:44
  • Wikipedia says it can be 8k: en.wikipedia.org/wiki/Ext3#Size_limits
    – dfrankow
    Apr 25, 2012 at 22:41
  • 1
    @dfrankow: if you have 8k memory pages, such as on Alpha hardware, yes. But you do not have those on x86 hardware and that is what I was talking about.
    – wzzrd
    Apr 26, 2012 at 8:03

To detect block size of required partition:

  1. Detect partition name:

    $ df -h

    for example we have /dev/sda1

  2. Detect block size for this partition:

    $ sudo blockdev --getbsz /dev/sda1
stat <<Filename>>

will also give file size in blocks

  • This is not what the OP asked
    – Pablo A
    Jul 3, 2019 at 7:55


sudo dumpe2fs /dev/sda1 | grep "Block size"

where /dev/sda1 is the device partition. You can get it from lsblk

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