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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)10.0.136.0/21
network10.0.136.0/21
broadcast10.0.143.255
first host10.0.136.1
last host10.0.143.254
subnet mask255.255.248.0
wildcard0.0.7.255
addresses2,048
usable hosts2,046
classA
ipcalc 10.0.136.0/21
address00001010.00000000.10001000.00000000
subnet mask11111111.11111111.11111000.00000000
network00001010.00000000.10001000.00000000
broadcast00001010.00000000.10001111.11111111
green = network part, grey = host part
hex0x0a008800
decimal167806976
reverse dns0.136.0.10.in-addr.arpa
ipv4-mapped::ffff:a00:8800

/21 split into /26 · 32 subnets

close ×
#networkhost rangebroadcast
110.0.136.0/2610.0.136.1 – 10.0.136.6210.0.136.63
210.0.136.64/2610.0.136.65 – 10.0.136.12610.0.136.127
310.0.136.128/2610.0.136.129 – 10.0.136.19010.0.136.191
410.0.136.192/2610.0.136.193 – 10.0.136.25410.0.136.255
510.0.137.0/2610.0.137.1 – 10.0.137.6210.0.137.63
610.0.137.64/2610.0.137.65 – 10.0.137.12610.0.137.127
710.0.137.128/2610.0.137.129 – 10.0.137.19010.0.137.191
810.0.137.192/2610.0.137.193 – 10.0.137.25410.0.137.255
910.0.138.0/2610.0.138.1 – 10.0.138.6210.0.138.63
1010.0.138.64/2610.0.138.65 – 10.0.138.12610.0.138.127
1110.0.138.128/2610.0.138.129 – 10.0.138.19010.0.138.191
1210.0.138.192/2610.0.138.193 – 10.0.138.25410.0.138.255
1310.0.139.0/2610.0.139.1 – 10.0.139.6210.0.139.63
1410.0.139.64/2610.0.139.65 – 10.0.139.12610.0.139.127
1510.0.139.128/2610.0.139.129 – 10.0.139.19010.0.139.191
1610.0.139.192/2610.0.139.193 – 10.0.139.25410.0.139.255
1710.0.140.0/2610.0.140.1 – 10.0.140.6210.0.140.63
1810.0.140.64/2610.0.140.65 – 10.0.140.12610.0.140.127
1910.0.140.128/2610.0.140.129 – 10.0.140.19010.0.140.191
2010.0.140.192/2610.0.140.193 – 10.0.140.25410.0.140.255
2110.0.141.0/2610.0.141.1 – 10.0.141.6210.0.141.63
2210.0.141.64/2610.0.141.65 – 10.0.141.12610.0.141.127
2310.0.141.128/2610.0.141.129 – 10.0.141.19010.0.141.191
2410.0.141.192/2610.0.141.193 – 10.0.141.25410.0.141.255
2510.0.142.0/2610.0.142.1 – 10.0.142.6210.0.142.63
2610.0.142.64/2610.0.142.65 – 10.0.142.12610.0.142.127
2710.0.142.128/2610.0.142.129 – 10.0.142.19010.0.142.191
2810.0.142.192/2610.0.142.193 – 10.0.142.25410.0.142.255
2910.0.143.0/2610.0.143.1 – 10.0.143.6210.0.143.63
3010.0.143.64/2610.0.143.65 – 10.0.143.12610.0.143.127
3110.0.143.128/2610.0.143.129 – 10.0.143.19010.0.143.191
3210.0.143.192/2610.0.143.193 – 10.0.143.25410.0.143.255
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 →