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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)10.6.40.0/21
network10.6.40.0/21
broadcast10.6.47.255
first host10.6.40.1
last host10.6.47.254
subnet mask255.255.248.0
wildcard0.0.7.255
addresses2,048
usable hosts2,046
classA
ipcalc 10.6.40.0/21
address00001010.00000110.00101000.00000000
subnet mask11111111.11111111.11111000.00000000
network00001010.00000110.00101000.00000000
broadcast00001010.00000110.00101111.11111111
green = network part, grey = host part
hex0x0a062800
decimal168175616
reverse dns0.40.6.10.in-addr.arpa
ipv4-mapped::ffff:a06:2800

/21 split into /26 · 32 subnets

close ×
#networkhost rangebroadcast
110.6.40.0/2610.6.40.1 – 10.6.40.6210.6.40.63
210.6.40.64/2610.6.40.65 – 10.6.40.12610.6.40.127
310.6.40.128/2610.6.40.129 – 10.6.40.19010.6.40.191
410.6.40.192/2610.6.40.193 – 10.6.40.25410.6.40.255
510.6.41.0/2610.6.41.1 – 10.6.41.6210.6.41.63
610.6.41.64/2610.6.41.65 – 10.6.41.12610.6.41.127
710.6.41.128/2610.6.41.129 – 10.6.41.19010.6.41.191
810.6.41.192/2610.6.41.193 – 10.6.41.25410.6.41.255
910.6.42.0/2610.6.42.1 – 10.6.42.6210.6.42.63
1010.6.42.64/2610.6.42.65 – 10.6.42.12610.6.42.127
1110.6.42.128/2610.6.42.129 – 10.6.42.19010.6.42.191
1210.6.42.192/2610.6.42.193 – 10.6.42.25410.6.42.255
1310.6.43.0/2610.6.43.1 – 10.6.43.6210.6.43.63
1410.6.43.64/2610.6.43.65 – 10.6.43.12610.6.43.127
1510.6.43.128/2610.6.43.129 – 10.6.43.19010.6.43.191
1610.6.43.192/2610.6.43.193 – 10.6.43.25410.6.43.255
1710.6.44.0/2610.6.44.1 – 10.6.44.6210.6.44.63
1810.6.44.64/2610.6.44.65 – 10.6.44.12610.6.44.127
1910.6.44.128/2610.6.44.129 – 10.6.44.19010.6.44.191
2010.6.44.192/2610.6.44.193 – 10.6.44.25410.6.44.255
2110.6.45.0/2610.6.45.1 – 10.6.45.6210.6.45.63
2210.6.45.64/2610.6.45.65 – 10.6.45.12610.6.45.127
2310.6.45.128/2610.6.45.129 – 10.6.45.19010.6.45.191
2410.6.45.192/2610.6.45.193 – 10.6.45.25410.6.45.255
2510.6.46.0/2610.6.46.1 – 10.6.46.6210.6.46.63
2610.6.46.64/2610.6.46.65 – 10.6.46.12610.6.46.127
2710.6.46.128/2610.6.46.129 – 10.6.46.19010.6.46.191
2810.6.46.192/2610.6.46.193 – 10.6.46.25410.6.46.255
2910.6.47.0/2610.6.47.1 – 10.6.47.6210.6.47.63
3010.6.47.64/2610.6.47.65 – 10.6.47.12610.6.47.127
3110.6.47.128/2610.6.47.129 – 10.6.47.19010.6.47.191
3210.6.47.192/2610.6.47.193 – 10.6.47.25410.6.47.255
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 →