ip
ipku.in

IPv4 Subnet Calculator

Enter an IP with a CIDR prefix or a subnet mask to see its network, broadcast, host range, and host count. You can also split the network into smaller subnets.

$ ipcalc
Try:192.168.1.10/2410.0.0.0/8172.16.5.4/20203.0.113.9/29
IPv6 calculator →
private IP (RFC 1918)10.0.128.0/21
network10.0.128.0/21
broadcast10.0.135.255
first host10.0.128.1
last host10.0.135.254
subnet mask255.255.248.0
wildcard0.0.7.255
addresses2,048
usable hosts2,046
classA
ipcalc 10.0.128.0/21
address00001010.00000000.10000000.00000000
subnet mask11111111.11111111.11111000.00000000
network00001010.00000000.10000000.00000000
broadcast00001010.00000000.10000111.11111111
green = network part, grey = host part
hex0x0a008000
decimal167804928
reverse dns0.128.0.10.in-addr.arpa
ipv4-mapped::ffff:a00:8000

/21 split into /26 · 32 subnets

close ×
#networkhost rangebroadcast
110.0.128.0/2610.0.128.1 – 10.0.128.6210.0.128.63
210.0.128.64/2610.0.128.65 – 10.0.128.12610.0.128.127
310.0.128.128/2610.0.128.129 – 10.0.128.19010.0.128.191
410.0.128.192/2610.0.128.193 – 10.0.128.25410.0.128.255
510.0.129.0/2610.0.129.1 – 10.0.129.6210.0.129.63
610.0.129.64/2610.0.129.65 – 10.0.129.12610.0.129.127
710.0.129.128/2610.0.129.129 – 10.0.129.19010.0.129.191
810.0.129.192/2610.0.129.193 – 10.0.129.25410.0.129.255
910.0.130.0/2610.0.130.1 – 10.0.130.6210.0.130.63
1010.0.130.64/2610.0.130.65 – 10.0.130.12610.0.130.127
1110.0.130.128/2610.0.130.129 – 10.0.130.19010.0.130.191
1210.0.130.192/2610.0.130.193 – 10.0.130.25410.0.130.255
1310.0.131.0/2610.0.131.1 – 10.0.131.6210.0.131.63
1410.0.131.64/2610.0.131.65 – 10.0.131.12610.0.131.127
1510.0.131.128/2610.0.131.129 – 10.0.131.19010.0.131.191
1610.0.131.192/2610.0.131.193 – 10.0.131.25410.0.131.255
1710.0.132.0/2610.0.132.1 – 10.0.132.6210.0.132.63
1810.0.132.64/2610.0.132.65 – 10.0.132.12610.0.132.127
1910.0.132.128/2610.0.132.129 – 10.0.132.19010.0.132.191
2010.0.132.192/2610.0.132.193 – 10.0.132.25410.0.132.255
2110.0.133.0/2610.0.133.1 – 10.0.133.6210.0.133.63
2210.0.133.64/2610.0.133.65 – 10.0.133.12610.0.133.127
2310.0.133.128/2610.0.133.129 – 10.0.133.19010.0.133.191
2410.0.133.192/2610.0.133.193 – 10.0.133.25410.0.133.255
2510.0.134.0/2610.0.134.1 – 10.0.134.6210.0.134.63
2610.0.134.64/2610.0.134.65 – 10.0.134.12610.0.134.127
2710.0.134.128/2610.0.134.129 – 10.0.134.19010.0.134.191
2810.0.134.192/2610.0.134.193 – 10.0.134.25410.0.134.255
2910.0.135.0/2610.0.135.1 – 10.0.135.6210.0.135.63
3010.0.135.64/2610.0.135.65 – 10.0.135.12610.0.135.127
3110.0.135.128/2610.0.135.129 – 10.0.135.19010.0.135.191
3210.0.135.192/2610.0.135.193 – 10.0.135.25410.0.135.255
01 / table

IPv4 CIDR prefix table.

Click a prefix longer than your network to split it into subnets.

prefixsubnet maskaddresseshostsin your /21
/00.0.0.04,294,967,2964,294,967,294-
/1128.0.0.02,147,483,6482,147,483,646-
/2192.0.0.01,073,741,8241,073,741,822-
/3224.0.0.0536,870,912536,870,910-
/4240.0.0.0268,435,456268,435,454-
/5248.0.0.0134,217,728134,217,726-
/6252.0.0.067,108,86467,108,862-
/7254.0.0.033,554,43233,554,430-
/8255.0.0.016,777,21616,777,214-
/9255.128.0.08,388,6088,388,606-
/10255.192.0.04,194,3044,194,302-
/11255.224.0.02,097,1522,097,150-
/12255.240.0.01,048,5761,048,574-
/13255.248.0.0524,288524,286-
/14255.252.0.0262,144262,142-
/15255.254.0.0131,072131,070-
/16255.255.0.065,53665,534-
/17255.255.128.032,76832,766-
/18255.255.192.016,38416,382-
/19255.255.224.08,1928,190-
/20255.255.240.04,0964,094-
/21255.255.248.02,0482,0461
/22255.255.252.01,0241,0222 split →
/23255.255.254.05125104 split →
/24255.255.255.02562548 split →
/25255.255.255.12812812616 split →
/26255.255.255.192646232 split →
/27255.255.255.224323064 split →
/28255.255.255.2401614128 split →
/29255.255.255.24886256 split →
/30255.255.255.25242512 split →
/31255.255.255.254221,024 split →
/32255.255.255.255112,048 split →
02 / faq

About this calculator.

How do I use this subnet calculator?

▼

Type an IP address followed by a prefix, like 192.168.1.10/24, or by a subnet mask, like 192.168.1.10 255.255.255.0. Without a prefix it uses /24. Click a row in the table to split the network into smaller subnets.

Why are usable hosts always 2 fewer?

▼

The first address in a subnet is the network address and the last is the broadcast address, so neither can go to a device. The exceptions are /31 (point-to-point links, RFC 3021) and /32 (a single address), which use every address.

Can I use it from a terminal?

▼

Yes. curl 'ipku.in/en/tools/ipv4-subnet-calculator?q=192.168.1.10/24' returns the result as plain text.

Learn how to work it out →