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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)10.0.248.0/21
network10.0.248.0/21
broadcast10.0.255.255
first host10.0.248.1
last host10.0.255.254
subnet mask255.255.248.0
wildcard0.0.7.255
addresses2,048
usable hosts2,046
classA
ipcalc 10.0.248.0/21
address00001010.00000000.11111000.00000000
subnet mask11111111.11111111.11111000.00000000
network00001010.00000000.11111000.00000000
broadcast00001010.00000000.11111111.11111111
green = network part, grey = host part
hex0x0a00f800
decimal167835648
reverse dns0.248.0.10.in-addr.arpa
ipv4-mapped::ffff:a00:f800

/21 split into /26 · 32 subnets

close ×
#networkhost rangebroadcast
110.0.248.0/2610.0.248.1 – 10.0.248.6210.0.248.63
210.0.248.64/2610.0.248.65 – 10.0.248.12610.0.248.127
310.0.248.128/2610.0.248.129 – 10.0.248.19010.0.248.191
410.0.248.192/2610.0.248.193 – 10.0.248.25410.0.248.255
510.0.249.0/2610.0.249.1 – 10.0.249.6210.0.249.63
610.0.249.64/2610.0.249.65 – 10.0.249.12610.0.249.127
710.0.249.128/2610.0.249.129 – 10.0.249.19010.0.249.191
810.0.249.192/2610.0.249.193 – 10.0.249.25410.0.249.255
910.0.250.0/2610.0.250.1 – 10.0.250.6210.0.250.63
1010.0.250.64/2610.0.250.65 – 10.0.250.12610.0.250.127
1110.0.250.128/2610.0.250.129 – 10.0.250.19010.0.250.191
1210.0.250.192/2610.0.250.193 – 10.0.250.25410.0.250.255
1310.0.251.0/2610.0.251.1 – 10.0.251.6210.0.251.63
1410.0.251.64/2610.0.251.65 – 10.0.251.12610.0.251.127
1510.0.251.128/2610.0.251.129 – 10.0.251.19010.0.251.191
1610.0.251.192/2610.0.251.193 – 10.0.251.25410.0.251.255
1710.0.252.0/2610.0.252.1 – 10.0.252.6210.0.252.63
1810.0.252.64/2610.0.252.65 – 10.0.252.12610.0.252.127
1910.0.252.128/2610.0.252.129 – 10.0.252.19010.0.252.191
2010.0.252.192/2610.0.252.193 – 10.0.252.25410.0.252.255
2110.0.253.0/2610.0.253.1 – 10.0.253.6210.0.253.63
2210.0.253.64/2610.0.253.65 – 10.0.253.12610.0.253.127
2310.0.253.128/2610.0.253.129 – 10.0.253.19010.0.253.191
2410.0.253.192/2610.0.253.193 – 10.0.253.25410.0.253.255
2510.0.254.0/2610.0.254.1 – 10.0.254.6210.0.254.63
2610.0.254.64/2610.0.254.65 – 10.0.254.12610.0.254.127
2710.0.254.128/2610.0.254.129 – 10.0.254.19010.0.254.191
2810.0.254.192/2610.0.254.193 – 10.0.254.25410.0.254.255
2910.0.255.0/2610.0.255.1 – 10.0.255.6210.0.255.63
3010.0.255.64/2610.0.255.65 – 10.0.255.12610.0.255.127
3110.0.255.128/2610.0.255.129 – 10.0.255.19010.0.255.191
3210.0.255.192/2610.0.255.193 – 10.0.255.25410.0.255.255
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 →