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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)10.1.56.0/21
network10.1.56.0/21
broadcast10.1.63.255
first host10.1.56.1
last host10.1.63.254
subnet mask255.255.248.0
wildcard0.0.7.255
addresses2,048
usable hosts2,046
classA
ipcalc 10.1.56.0/21
address00001010.00000001.00111000.00000000
subnet mask11111111.11111111.11111000.00000000
network00001010.00000001.00111000.00000000
broadcast00001010.00000001.00111111.11111111
green = network part, grey = host part
hex0x0a013800
decimal167852032
reverse dns0.56.1.10.in-addr.arpa
ipv4-mapped::ffff:a01:3800

/21 split into /27 · 64 subnets

close ×
#networkhost rangebroadcast
110.1.56.0/2710.1.56.1 – 10.1.56.3010.1.56.31
210.1.56.32/2710.1.56.33 – 10.1.56.6210.1.56.63
310.1.56.64/2710.1.56.65 – 10.1.56.9410.1.56.95
410.1.56.96/2710.1.56.97 – 10.1.56.12610.1.56.127
510.1.56.128/2710.1.56.129 – 10.1.56.15810.1.56.159
610.1.56.160/2710.1.56.161 – 10.1.56.19010.1.56.191
710.1.56.192/2710.1.56.193 – 10.1.56.22210.1.56.223
810.1.56.224/2710.1.56.225 – 10.1.56.25410.1.56.255
910.1.57.0/2710.1.57.1 – 10.1.57.3010.1.57.31
1010.1.57.32/2710.1.57.33 – 10.1.57.6210.1.57.63
1110.1.57.64/2710.1.57.65 – 10.1.57.9410.1.57.95
1210.1.57.96/2710.1.57.97 – 10.1.57.12610.1.57.127
1310.1.57.128/2710.1.57.129 – 10.1.57.15810.1.57.159
1410.1.57.160/2710.1.57.161 – 10.1.57.19010.1.57.191
1510.1.57.192/2710.1.57.193 – 10.1.57.22210.1.57.223
1610.1.57.224/2710.1.57.225 – 10.1.57.25410.1.57.255
1710.1.58.0/2710.1.58.1 – 10.1.58.3010.1.58.31
1810.1.58.32/2710.1.58.33 – 10.1.58.6210.1.58.63
1910.1.58.64/2710.1.58.65 – 10.1.58.9410.1.58.95
2010.1.58.96/2710.1.58.97 – 10.1.58.12610.1.58.127
2110.1.58.128/2710.1.58.129 – 10.1.58.15810.1.58.159
2210.1.58.160/2710.1.58.161 – 10.1.58.19010.1.58.191
2310.1.58.192/2710.1.58.193 – 10.1.58.22210.1.58.223
2410.1.58.224/2710.1.58.225 – 10.1.58.25410.1.58.255
2510.1.59.0/2710.1.59.1 – 10.1.59.3010.1.59.31
2610.1.59.32/2710.1.59.33 – 10.1.59.6210.1.59.63
2710.1.59.64/2710.1.59.65 – 10.1.59.9410.1.59.95
2810.1.59.96/2710.1.59.97 – 10.1.59.12610.1.59.127
2910.1.59.128/2710.1.59.129 – 10.1.59.15810.1.59.159
3010.1.59.160/2710.1.59.161 – 10.1.59.19010.1.59.191
3110.1.59.192/2710.1.59.193 – 10.1.59.22210.1.59.223
3210.1.59.224/2710.1.59.225 – 10.1.59.25410.1.59.255
3310.1.60.0/2710.1.60.1 – 10.1.60.3010.1.60.31
3410.1.60.32/2710.1.60.33 – 10.1.60.6210.1.60.63
3510.1.60.64/2710.1.60.65 – 10.1.60.9410.1.60.95
3610.1.60.96/2710.1.60.97 – 10.1.60.12610.1.60.127
3710.1.60.128/2710.1.60.129 – 10.1.60.15810.1.60.159
3810.1.60.160/2710.1.60.161 – 10.1.60.19010.1.60.191
3910.1.60.192/2710.1.60.193 – 10.1.60.22210.1.60.223
4010.1.60.224/2710.1.60.225 – 10.1.60.25410.1.60.255
4110.1.61.0/2710.1.61.1 – 10.1.61.3010.1.61.31
4210.1.61.32/2710.1.61.33 – 10.1.61.6210.1.61.63
4310.1.61.64/2710.1.61.65 – 10.1.61.9410.1.61.95
4410.1.61.96/2710.1.61.97 – 10.1.61.12610.1.61.127
4510.1.61.128/2710.1.61.129 – 10.1.61.15810.1.61.159
4610.1.61.160/2710.1.61.161 – 10.1.61.19010.1.61.191
4710.1.61.192/2710.1.61.193 – 10.1.61.22210.1.61.223
4810.1.61.224/2710.1.61.225 – 10.1.61.25410.1.61.255
4910.1.62.0/2710.1.62.1 – 10.1.62.3010.1.62.31
5010.1.62.32/2710.1.62.33 – 10.1.62.6210.1.62.63
5110.1.62.64/2710.1.62.65 – 10.1.62.9410.1.62.95
5210.1.62.96/2710.1.62.97 – 10.1.62.12610.1.62.127
5310.1.62.128/2710.1.62.129 – 10.1.62.15810.1.62.159
5410.1.62.160/2710.1.62.161 – 10.1.62.19010.1.62.191
5510.1.62.192/2710.1.62.193 – 10.1.62.22210.1.62.223
5610.1.62.224/2710.1.62.225 – 10.1.62.25410.1.62.255
5710.1.63.0/2710.1.63.1 – 10.1.63.3010.1.63.31
5810.1.63.32/2710.1.63.33 – 10.1.63.6210.1.63.63
5910.1.63.64/2710.1.63.65 – 10.1.63.9410.1.63.95
6010.1.63.96/2710.1.63.97 – 10.1.63.12610.1.63.127
6110.1.63.128/2710.1.63.129 – 10.1.63.15810.1.63.159
6210.1.63.160/2710.1.63.161 – 10.1.63.19010.1.63.191
6310.1.63.192/2710.1.63.193 – 10.1.63.22210.1.63.223
6410.1.63.224/2710.1.63.225 – 10.1.63.25410.1.63.255
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 →