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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)10.3.208.0/21
network10.3.208.0/21
broadcast10.3.215.255
first host10.3.208.1
last host10.3.215.254
subnet mask255.255.248.0
wildcard0.0.7.255
addresses2,048
usable hosts2,046
classA
ipcalc 10.3.208.0/21
address00001010.00000011.11010000.00000000
subnet mask11111111.11111111.11111000.00000000
network00001010.00000011.11010000.00000000
broadcast00001010.00000011.11010111.11111111
green = network part, grey = host part
hex0x0a03d000
decimal168022016
reverse dns0.208.3.10.in-addr.arpa
ipv4-mapped::ffff:a03:d000

/21 split into /26 · 32 subnets

close ×
#networkhost rangebroadcast
110.3.208.0/2610.3.208.1 – 10.3.208.6210.3.208.63
210.3.208.64/2610.3.208.65 – 10.3.208.12610.3.208.127
310.3.208.128/2610.3.208.129 – 10.3.208.19010.3.208.191
410.3.208.192/2610.3.208.193 – 10.3.208.25410.3.208.255
510.3.209.0/2610.3.209.1 – 10.3.209.6210.3.209.63
610.3.209.64/2610.3.209.65 – 10.3.209.12610.3.209.127
710.3.209.128/2610.3.209.129 – 10.3.209.19010.3.209.191
810.3.209.192/2610.3.209.193 – 10.3.209.25410.3.209.255
910.3.210.0/2610.3.210.1 – 10.3.210.6210.3.210.63
1010.3.210.64/2610.3.210.65 – 10.3.210.12610.3.210.127
1110.3.210.128/2610.3.210.129 – 10.3.210.19010.3.210.191
1210.3.210.192/2610.3.210.193 – 10.3.210.25410.3.210.255
1310.3.211.0/2610.3.211.1 – 10.3.211.6210.3.211.63
1410.3.211.64/2610.3.211.65 – 10.3.211.12610.3.211.127
1510.3.211.128/2610.3.211.129 – 10.3.211.19010.3.211.191
1610.3.211.192/2610.3.211.193 – 10.3.211.25410.3.211.255
1710.3.212.0/2610.3.212.1 – 10.3.212.6210.3.212.63
1810.3.212.64/2610.3.212.65 – 10.3.212.12610.3.212.127
1910.3.212.128/2610.3.212.129 – 10.3.212.19010.3.212.191
2010.3.212.192/2610.3.212.193 – 10.3.212.25410.3.212.255
2110.3.213.0/2610.3.213.1 – 10.3.213.6210.3.213.63
2210.3.213.64/2610.3.213.65 – 10.3.213.12610.3.213.127
2310.3.213.128/2610.3.213.129 – 10.3.213.19010.3.213.191
2410.3.213.192/2610.3.213.193 – 10.3.213.25410.3.213.255
2510.3.214.0/2610.3.214.1 – 10.3.214.6210.3.214.63
2610.3.214.64/2610.3.214.65 – 10.3.214.12610.3.214.127
2710.3.214.128/2610.3.214.129 – 10.3.214.19010.3.214.191
2810.3.214.192/2610.3.214.193 – 10.3.214.25410.3.214.255
2910.3.215.0/2610.3.215.1 – 10.3.215.6210.3.215.63
3010.3.215.64/2610.3.215.65 – 10.3.215.12610.3.215.127
3110.3.215.128/2610.3.215.129 – 10.3.215.19010.3.215.191
3210.3.215.192/2610.3.215.193 – 10.3.215.25410.3.215.255
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 →