Why fdisk and lsblk show different partition size?

Question

If we see the size of sdb2 is 39.5GB in fdisk whereas 1k in the lsblk output. What can be the reason for this?

Disk /dev/sdb: 300 GiB, 322122547200 bytes, 629145600 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x674589c1

Device     Boot   Start      End  Sectors  Size Id Type
/dev/sdb1  *       2048   999423   997376  487M 83 Linux
/dev/sdb2       1001470 83884031 82882562 39.5G  5 Extended
/dev/sdb5       1001472 83884031 82882560 39.5G 8e Linux LVM


root@ubuntu1604:~# lsblk
NAME                      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
fd0                         2:0    1    4K  0 disk
sda                         8:0    0  300G  0 disk
sdb                         8:16   0  300G  0 disk
├─sdb1                      8:17   0  487M  0 part /boot
├─sdb2                      8:18   0    1K  0 part
└─sdb5                      8:21   0 39.5G  0 part
  ├─ubuntu1604--vg-root   252:0    0 35.5G  0 lvm  /
  └─ubuntu1604--vg-swap_1 252:1    0    4G  0 lvm  [SWAP]
sr0                        11:0    1 1024M  0 rom
root@ubuntu1604:~#

Answer 1

lsblk shows size in IEC units (GiB, MiB, etc). A gibibyte (GiB) is larger than a gigabyte (GB)
fdisk shows size in SI (GB, MB, etc).