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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)10.2.240.0/21
network10.2.240.0/21
broadcast10.2.247.255
first host10.2.240.1
last host10.2.247.254
subnet mask255.255.248.0
wildcard0.0.7.255
addresses2,048
usable hosts2,046
classA
ipcalc 10.2.240.0/21
address00001010.00000010.11110000.00000000
subnet mask11111111.11111111.11111000.00000000
network00001010.00000010.11110000.00000000
broadcast00001010.00000010.11110111.11111111
green = network part, grey = host part
hex0x0a02f000
decimal167964672
reverse dns0.240.2.10.in-addr.arpa
ipv4-mapped::ffff:a02:f000

/21 split into /26 · 32 subnets

close ×
#networkhost rangebroadcast
110.2.240.0/2610.2.240.1 – 10.2.240.6210.2.240.63
210.2.240.64/2610.2.240.65 – 10.2.240.12610.2.240.127
310.2.240.128/2610.2.240.129 – 10.2.240.19010.2.240.191
410.2.240.192/2610.2.240.193 – 10.2.240.25410.2.240.255
510.2.241.0/2610.2.241.1 – 10.2.241.6210.2.241.63
610.2.241.64/2610.2.241.65 – 10.2.241.12610.2.241.127
710.2.241.128/2610.2.241.129 – 10.2.241.19010.2.241.191
810.2.241.192/2610.2.241.193 – 10.2.241.25410.2.241.255
910.2.242.0/2610.2.242.1 – 10.2.242.6210.2.242.63
1010.2.242.64/2610.2.242.65 – 10.2.242.12610.2.242.127
1110.2.242.128/2610.2.242.129 – 10.2.242.19010.2.242.191
1210.2.242.192/2610.2.242.193 – 10.2.242.25410.2.242.255
1310.2.243.0/2610.2.243.1 – 10.2.243.6210.2.243.63
1410.2.243.64/2610.2.243.65 – 10.2.243.12610.2.243.127
1510.2.243.128/2610.2.243.129 – 10.2.243.19010.2.243.191
1610.2.243.192/2610.2.243.193 – 10.2.243.25410.2.243.255
1710.2.244.0/2610.2.244.1 – 10.2.244.6210.2.244.63
1810.2.244.64/2610.2.244.65 – 10.2.244.12610.2.244.127
1910.2.244.128/2610.2.244.129 – 10.2.244.19010.2.244.191
2010.2.244.192/2610.2.244.193 – 10.2.244.25410.2.244.255
2110.2.245.0/2610.2.245.1 – 10.2.245.6210.2.245.63
2210.2.245.64/2610.2.245.65 – 10.2.245.12610.2.245.127
2310.2.245.128/2610.2.245.129 – 10.2.245.19010.2.245.191
2410.2.245.192/2610.2.245.193 – 10.2.245.25410.2.245.255
2510.2.246.0/2610.2.246.1 – 10.2.246.6210.2.246.63
2610.2.246.64/2610.2.246.65 – 10.2.246.12610.2.246.127
2710.2.246.128/2610.2.246.129 – 10.2.246.19010.2.246.191
2810.2.246.192/2610.2.246.193 – 10.2.246.25410.2.246.255
2910.2.247.0/2610.2.247.1 – 10.2.247.6210.2.247.63
3010.2.247.64/2610.2.247.65 – 10.2.247.12610.2.247.127
3110.2.247.128/2610.2.247.129 – 10.2.247.19010.2.247.191
3210.2.247.192/2610.2.247.193 – 10.2.247.25410.2.247.255
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 →