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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)10.2.40.0/21
network10.2.40.0/21
broadcast10.2.47.255
first host10.2.40.1
last host10.2.47.254
subnet mask255.255.248.0
wildcard0.0.7.255
addresses2,048
usable hosts2,046
classA
ipcalc 10.2.40.0/21
address00001010.00000010.00101000.00000000
subnet mask11111111.11111111.11111000.00000000
network00001010.00000010.00101000.00000000
broadcast00001010.00000010.00101111.11111111
green = network part, grey = host part
hex0x0a022800
decimal167913472
reverse dns0.40.2.10.in-addr.arpa
ipv4-mapped::ffff:a02:2800

/21 split into /27 · 64 subnets

close ×
#networkhost rangebroadcast
110.2.40.0/2710.2.40.1 – 10.2.40.3010.2.40.31
210.2.40.32/2710.2.40.33 – 10.2.40.6210.2.40.63
310.2.40.64/2710.2.40.65 – 10.2.40.9410.2.40.95
410.2.40.96/2710.2.40.97 – 10.2.40.12610.2.40.127
510.2.40.128/2710.2.40.129 – 10.2.40.15810.2.40.159
610.2.40.160/2710.2.40.161 – 10.2.40.19010.2.40.191
710.2.40.192/2710.2.40.193 – 10.2.40.22210.2.40.223
810.2.40.224/2710.2.40.225 – 10.2.40.25410.2.40.255
910.2.41.0/2710.2.41.1 – 10.2.41.3010.2.41.31
1010.2.41.32/2710.2.41.33 – 10.2.41.6210.2.41.63
1110.2.41.64/2710.2.41.65 – 10.2.41.9410.2.41.95
1210.2.41.96/2710.2.41.97 – 10.2.41.12610.2.41.127
1310.2.41.128/2710.2.41.129 – 10.2.41.15810.2.41.159
1410.2.41.160/2710.2.41.161 – 10.2.41.19010.2.41.191
1510.2.41.192/2710.2.41.193 – 10.2.41.22210.2.41.223
1610.2.41.224/2710.2.41.225 – 10.2.41.25410.2.41.255
1710.2.42.0/2710.2.42.1 – 10.2.42.3010.2.42.31
1810.2.42.32/2710.2.42.33 – 10.2.42.6210.2.42.63
1910.2.42.64/2710.2.42.65 – 10.2.42.9410.2.42.95
2010.2.42.96/2710.2.42.97 – 10.2.42.12610.2.42.127
2110.2.42.128/2710.2.42.129 – 10.2.42.15810.2.42.159
2210.2.42.160/2710.2.42.161 – 10.2.42.19010.2.42.191
2310.2.42.192/2710.2.42.193 – 10.2.42.22210.2.42.223
2410.2.42.224/2710.2.42.225 – 10.2.42.25410.2.42.255
2510.2.43.0/2710.2.43.1 – 10.2.43.3010.2.43.31
2610.2.43.32/2710.2.43.33 – 10.2.43.6210.2.43.63
2710.2.43.64/2710.2.43.65 – 10.2.43.9410.2.43.95
2810.2.43.96/2710.2.43.97 – 10.2.43.12610.2.43.127
2910.2.43.128/2710.2.43.129 – 10.2.43.15810.2.43.159
3010.2.43.160/2710.2.43.161 – 10.2.43.19010.2.43.191
3110.2.43.192/2710.2.43.193 – 10.2.43.22210.2.43.223
3210.2.43.224/2710.2.43.225 – 10.2.43.25410.2.43.255
3310.2.44.0/2710.2.44.1 – 10.2.44.3010.2.44.31
3410.2.44.32/2710.2.44.33 – 10.2.44.6210.2.44.63
3510.2.44.64/2710.2.44.65 – 10.2.44.9410.2.44.95
3610.2.44.96/2710.2.44.97 – 10.2.44.12610.2.44.127
3710.2.44.128/2710.2.44.129 – 10.2.44.15810.2.44.159
3810.2.44.160/2710.2.44.161 – 10.2.44.19010.2.44.191
3910.2.44.192/2710.2.44.193 – 10.2.44.22210.2.44.223
4010.2.44.224/2710.2.44.225 – 10.2.44.25410.2.44.255
4110.2.45.0/2710.2.45.1 – 10.2.45.3010.2.45.31
4210.2.45.32/2710.2.45.33 – 10.2.45.6210.2.45.63
4310.2.45.64/2710.2.45.65 – 10.2.45.9410.2.45.95
4410.2.45.96/2710.2.45.97 – 10.2.45.12610.2.45.127
4510.2.45.128/2710.2.45.129 – 10.2.45.15810.2.45.159
4610.2.45.160/2710.2.45.161 – 10.2.45.19010.2.45.191
4710.2.45.192/2710.2.45.193 – 10.2.45.22210.2.45.223
4810.2.45.224/2710.2.45.225 – 10.2.45.25410.2.45.255
4910.2.46.0/2710.2.46.1 – 10.2.46.3010.2.46.31
5010.2.46.32/2710.2.46.33 – 10.2.46.6210.2.46.63
5110.2.46.64/2710.2.46.65 – 10.2.46.9410.2.46.95
5210.2.46.96/2710.2.46.97 – 10.2.46.12610.2.46.127
5310.2.46.128/2710.2.46.129 – 10.2.46.15810.2.46.159
5410.2.46.160/2710.2.46.161 – 10.2.46.19010.2.46.191
5510.2.46.192/2710.2.46.193 – 10.2.46.22210.2.46.223
5610.2.46.224/2710.2.46.225 – 10.2.46.25410.2.46.255
5710.2.47.0/2710.2.47.1 – 10.2.47.3010.2.47.31
5810.2.47.32/2710.2.47.33 – 10.2.47.6210.2.47.63
5910.2.47.64/2710.2.47.65 – 10.2.47.9410.2.47.95
6010.2.47.96/2710.2.47.97 – 10.2.47.12610.2.47.127
6110.2.47.128/2710.2.47.129 – 10.2.47.15810.2.47.159
6210.2.47.160/2710.2.47.161 – 10.2.47.19010.2.47.191
6310.2.47.192/2710.2.47.193 – 10.2.47.22210.2.47.223
6410.2.47.224/2710.2.47.225 – 10.2.47.25410.2.47.255
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 →