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IP subnet calculator

Type an address with its prefix or mask to see the network, its usable range and masks. Split it into smaller subnets, or look up any prefix in the reference tables.

Network40.0.0.0/7
Usable hosts33,554,430
Subnet mask254.0.0.0
Addresses33,554,432
Network address
40.0.0.0
Broadcast address
41.255.255.255
First usable
40.0.0.1
Last usable
41.255.255.254
Usable hosts
33,554,430 (33,554,432 less the network and broadcast addresses)
Subnet mask
254.0.0.0
Wildcard mask
1.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/7
Type
Public public
Old class
A (default /8)
As numbers
Hex 28000000 · Integer 671088640 to 704643071
Reverse DNS zones
40.in-addr.arpa
41.in-addr.arpa
/7 is not on a 8-bit boundary, so it takes 2 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00101000.00000000.00000000.0000000040.0.0.0
Subnet mask11111110.00000000.00000000.00000000254.0.0.0
Network00101000.00000000.00000000.0000000040.0.0.0
Broadcast00101001.11111111.11111111.1111111141.255.255.255
Split into smaller subnets/14
/8 (2)/9 (4)/10 (8)/11 (16)/12 (32)/13 (64)/14 (128)/15 (256)/16 (512)/17 (1,024)/18 (2,048)/19 (4,096)

40.0.0.0/7 makes 128 subnets of /14.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
140.0.0.0/1440.0.0.1 to 40.3.255.25440.3.255.255262,142
240.4.0.0/1440.4.0.1 to 40.7.255.25440.7.255.255262,142
340.8.0.0/1440.8.0.1 to 40.11.255.25440.11.255.255262,142
440.12.0.0/1440.12.0.1 to 40.15.255.25440.15.255.255262,142
540.16.0.0/1440.16.0.1 to 40.19.255.25440.19.255.255262,142
640.20.0.0/1440.20.0.1 to 40.23.255.25440.23.255.255262,142
740.24.0.0/1440.24.0.1 to 40.27.255.25440.27.255.255262,142
840.28.0.0/1440.28.0.1 to 40.31.255.25440.31.255.255262,142
940.32.0.0/1440.32.0.1 to 40.35.255.25440.35.255.255262,142
1040.36.0.0/1440.36.0.1 to 40.39.255.25440.39.255.255262,142
1140.40.0.0/1440.40.0.1 to 40.43.255.25440.43.255.255262,142
1240.44.0.0/1440.44.0.1 to 40.47.255.25440.47.255.255262,142
1340.48.0.0/1440.48.0.1 to 40.51.255.25440.51.255.255262,142
1440.52.0.0/1440.52.0.1 to 40.55.255.25440.55.255.255262,142
1540.56.0.0/1440.56.0.1 to 40.59.255.25440.59.255.255262,142
1640.60.0.0/1440.60.0.1 to 40.63.255.25440.63.255.255262,142
1740.64.0.0/1440.64.0.1 to 40.67.255.25440.67.255.255262,142
1840.68.0.0/1440.68.0.1 to 40.71.255.25440.71.255.255262,142
1940.72.0.0/1440.72.0.1 to 40.75.255.25440.75.255.255262,142
2040.76.0.0/1440.76.0.1 to 40.79.255.25440.79.255.255262,142
2140.80.0.0/1440.80.0.1 to 40.83.255.25440.83.255.255262,142
2240.84.0.0/1440.84.0.1 to 40.87.255.25440.87.255.255262,142
2340.88.0.0/1440.88.0.1 to 40.91.255.25440.91.255.255262,142
2440.92.0.0/1440.92.0.1 to 40.95.255.25440.95.255.255262,142
2540.96.0.0/1440.96.0.1 to 40.99.255.25440.99.255.255262,142
2640.100.0.0/1440.100.0.1 to 40.103.255.25440.103.255.255262,142
2740.104.0.0/1440.104.0.1 to 40.107.255.25440.107.255.255262,142
2840.108.0.0/1440.108.0.1 to 40.111.255.25440.111.255.255262,142
2940.112.0.0/1440.112.0.1 to 40.115.255.25440.115.255.255262,142
3040.116.0.0/1440.116.0.1 to 40.119.255.25440.119.255.255262,142
3140.120.0.0/1440.120.0.1 to 40.123.255.25440.123.255.255262,142
3240.124.0.0/1440.124.0.1 to 40.127.255.25440.127.255.255262,142
3340.128.0.0/1440.128.0.1 to 40.131.255.25440.131.255.255262,142
3440.132.0.0/1440.132.0.1 to 40.135.255.25440.135.255.255262,142
3540.136.0.0/1440.136.0.1 to 40.139.255.25440.139.255.255262,142
3640.140.0.0/1440.140.0.1 to 40.143.255.25440.143.255.255262,142
3740.144.0.0/1440.144.0.1 to 40.147.255.25440.147.255.255262,142
3840.148.0.0/1440.148.0.1 to 40.151.255.25440.151.255.255262,142
3940.152.0.0/1440.152.0.1 to 40.155.255.25440.155.255.255262,142
4040.156.0.0/1440.156.0.1 to 40.159.255.25440.159.255.255262,142
4140.160.0.0/1440.160.0.1 to 40.163.255.25440.163.255.255262,142
4240.164.0.0/1440.164.0.1 to 40.167.255.25440.167.255.255262,142
4340.168.0.0/1440.168.0.1 to 40.171.255.25440.171.255.255262,142
4440.172.0.0/1440.172.0.1 to 40.175.255.25440.175.255.255262,142
4540.176.0.0/1440.176.0.1 to 40.179.255.25440.179.255.255262,142
4640.180.0.0/1440.180.0.1 to 40.183.255.25440.183.255.255262,142
4740.184.0.0/1440.184.0.1 to 40.187.255.25440.187.255.255262,142
4840.188.0.0/1440.188.0.1 to 40.191.255.25440.191.255.255262,142
4940.192.0.0/1440.192.0.1 to 40.195.255.25440.195.255.255262,142
5040.196.0.0/1440.196.0.1 to 40.199.255.25440.199.255.255262,142
5140.200.0.0/1440.200.0.1 to 40.203.255.25440.203.255.255262,142
5240.204.0.0/1440.204.0.1 to 40.207.255.25440.207.255.255262,142
5340.208.0.0/1440.208.0.1 to 40.211.255.25440.211.255.255262,142
5440.212.0.0/1440.212.0.1 to 40.215.255.25440.215.255.255262,142
5540.216.0.0/1440.216.0.1 to 40.219.255.25440.219.255.255262,142
5640.220.0.0/1440.220.0.1 to 40.223.255.25440.223.255.255262,142
5740.224.0.0/1440.224.0.1 to 40.227.255.25440.227.255.255262,142
5840.228.0.0/1440.228.0.1 to 40.231.255.25440.231.255.255262,142
5940.232.0.0/1440.232.0.1 to 40.235.255.25440.235.255.255262,142
6040.236.0.0/1440.236.0.1 to 40.239.255.25440.239.255.255262,142
6140.240.0.0/1440.240.0.1 to 40.243.255.25440.243.255.255262,142
6240.244.0.0/1440.244.0.1 to 40.247.255.25440.247.255.255262,142
6340.248.0.0/1440.248.0.1 to 40.251.255.25440.251.255.255262,142
6440.252.0.0/1440.252.0.1 to 40.255.255.25440.255.255.255262,142
6541.0.0.0/1441.0.0.1 to 41.3.255.25441.3.255.255262,142
6641.4.0.0/1441.4.0.1 to 41.7.255.25441.7.255.255262,142
6741.8.0.0/1441.8.0.1 to 41.11.255.25441.11.255.255262,142
6841.12.0.0/1441.12.0.1 to 41.15.255.25441.15.255.255262,142
6941.16.0.0/1441.16.0.1 to 41.19.255.25441.19.255.255262,142
7041.20.0.0/1441.20.0.1 to 41.23.255.25441.23.255.255262,142
7141.24.0.0/1441.24.0.1 to 41.27.255.25441.27.255.255262,142
7241.28.0.0/1441.28.0.1 to 41.31.255.25441.31.255.255262,142
7341.32.0.0/1441.32.0.1 to 41.35.255.25441.35.255.255262,142
7441.36.0.0/1441.36.0.1 to 41.39.255.25441.39.255.255262,142
7541.40.0.0/1441.40.0.1 to 41.43.255.25441.43.255.255262,142
7641.44.0.0/1441.44.0.1 to 41.47.255.25441.47.255.255262,142
7741.48.0.0/1441.48.0.1 to 41.51.255.25441.51.255.255262,142
7841.52.0.0/1441.52.0.1 to 41.55.255.25441.55.255.255262,142
7941.56.0.0/1441.56.0.1 to 41.59.255.25441.59.255.255262,142
8041.60.0.0/1441.60.0.1 to 41.63.255.25441.63.255.255262,142
8141.64.0.0/1441.64.0.1 to 41.67.255.25441.67.255.255262,142
8241.68.0.0/1441.68.0.1 to 41.71.255.25441.71.255.255262,142
8341.72.0.0/1441.72.0.1 to 41.75.255.25441.75.255.255262,142
8441.76.0.0/1441.76.0.1 to 41.79.255.25441.79.255.255262,142
8541.80.0.0/1441.80.0.1 to 41.83.255.25441.83.255.255262,142
8641.84.0.0/1441.84.0.1 to 41.87.255.25441.87.255.255262,142
8741.88.0.0/1441.88.0.1 to 41.91.255.25441.91.255.255262,142
8841.92.0.0/1441.92.0.1 to 41.95.255.25441.95.255.255262,142
8941.96.0.0/1441.96.0.1 to 41.99.255.25441.99.255.255262,142
9041.100.0.0/1441.100.0.1 to 41.103.255.25441.103.255.255262,142
9141.104.0.0/1441.104.0.1 to 41.107.255.25441.107.255.255262,142
9241.108.0.0/1441.108.0.1 to 41.111.255.25441.111.255.255262,142
9341.112.0.0/1441.112.0.1 to 41.115.255.25441.115.255.255262,142
9441.116.0.0/1441.116.0.1 to 41.119.255.25441.119.255.255262,142
9541.120.0.0/1441.120.0.1 to 41.123.255.25441.123.255.255262,142
9641.124.0.0/1441.124.0.1 to 41.127.255.25441.127.255.255262,142
9741.128.0.0/1441.128.0.1 to 41.131.255.25441.131.255.255262,142
9841.132.0.0/1441.132.0.1 to 41.135.255.25441.135.255.255262,142
9941.136.0.0/1441.136.0.1 to 41.139.255.25441.139.255.255262,142
10041.140.0.0/1441.140.0.1 to 41.143.255.25441.143.255.255262,142
10141.144.0.0/1441.144.0.1 to 41.147.255.25441.147.255.255262,142
10241.148.0.0/1441.148.0.1 to 41.151.255.25441.151.255.255262,142
10341.152.0.0/1441.152.0.1 to 41.155.255.25441.155.255.255262,142
10441.156.0.0/1441.156.0.1 to 41.159.255.25441.159.255.255262,142
10541.160.0.0/1441.160.0.1 to 41.163.255.25441.163.255.255262,142
10641.164.0.0/1441.164.0.1 to 41.167.255.25441.167.255.255262,142
10741.168.0.0/1441.168.0.1 to 41.171.255.25441.171.255.255262,142
10841.172.0.0/1441.172.0.1 to 41.175.255.25441.175.255.255262,142
10941.176.0.0/1441.176.0.1 to 41.179.255.25441.179.255.255262,142
11041.180.0.0/1441.180.0.1 to 41.183.255.25441.183.255.255262,142
11141.184.0.0/1441.184.0.1 to 41.187.255.25441.187.255.255262,142
11241.188.0.0/1441.188.0.1 to 41.191.255.25441.191.255.255262,142
11341.192.0.0/1441.192.0.1 to 41.195.255.25441.195.255.255262,142
11441.196.0.0/1441.196.0.1 to 41.199.255.25441.199.255.255262,142
11541.200.0.0/1441.200.0.1 to 41.203.255.25441.203.255.255262,142
11641.204.0.0/1441.204.0.1 to 41.207.255.25441.207.255.255262,142
11741.208.0.0/1441.208.0.1 to 41.211.255.25441.211.255.255262,142
11841.212.0.0/1441.212.0.1 to 41.215.255.25441.215.255.255262,142
11941.216.0.0/1441.216.0.1 to 41.219.255.25441.219.255.255262,142
12041.220.0.0/1441.220.0.1 to 41.223.255.25441.223.255.255262,142
12141.224.0.0/1441.224.0.1 to 41.227.255.25441.227.255.255262,142
12241.228.0.0/1441.228.0.1 to 41.231.255.25441.231.255.255262,142
12341.232.0.0/1441.232.0.1 to 41.235.255.25441.235.255.255262,142
12441.236.0.0/1441.236.0.1 to 41.239.255.25441.239.255.255262,142
12541.240.0.0/1441.240.0.1 to 41.243.255.25441.243.255.255262,142
12641.244.0.0/1441.244.0.1 to 41.247.255.25441.247.255.255262,142
12741.248.0.0/1441.248.0.1 to 41.251.255.25441.251.255.255262,142
12841.252.0.0/1441.252.0.1 to 41.255.255.25441.255.255.255262,142

IPv4 CIDR reference (/0 to /32)

IPv4 prefix lengths
PrefixSubnet maskWildcardAddressesUsable hostsSizeTypical use
/00.0.0.0255.255.255.2554,294,967,2964,294,967,29416,777,216 × /24
/1128.0.0.0127.255.255.2552,147,483,6482,147,483,6468,388,608 × /24
/2192.0.0.063.255.255.2551,073,741,8241,073,741,8224,194,304 × /24
/3224.0.0.031.255.255.255536,870,912536,870,9102,097,152 × /24
/4240.0.0.015.255.255.255268,435,456268,435,4541,048,576 × /24
/5248.0.0.07.255.255.255134,217,728134,217,726524,288 × /24
/6252.0.0.03.255.255.25567,108,86467,108,862262,144 × /24
/7254.0.0.01.255.255.25533,554,43233,554,430131,072 × /24
/8255.0.0.00.255.255.25516,777,21616,777,21465,536 × /24Old class A; 10.0.0.0/8
/9255.128.0.00.127.255.2558,388,6088,388,60632,768 × /24
/10255.192.0.00.63.255.2554,194,3044,194,30216,384 × /24
/11255.224.0.00.31.255.2552,097,1522,097,1508,192 × /24
/12255.240.0.00.15.255.2551,048,5761,048,5744,096 × /24172.16.0.0/12
/13255.248.0.00.7.255.255524,288524,2862,048 × /24
/14255.252.0.00.3.255.255262,144262,1421,024 × /24
/15255.254.0.00.1.255.255131,072131,070512 × /24
/16255.255.0.00.0.255.25565,53665,534256 × /24Old class B; 192.168.0.0/16
/17255.255.128.00.0.127.25532,76832,766128 × /24
/18255.255.192.00.0.63.25516,38416,38264 × /24
/19255.255.224.00.0.31.2558,1928,19032 × /24
/20255.255.240.00.0.15.2554,0964,09416 × /24
/21255.255.248.00.0.7.2552,0482,0468 × /24
/22255.255.252.00.0.3.2551,0241,0224 × /24Large office or guest Wi-Fi (1,022 hosts)
/23255.255.254.00.0.1.2555125102 × /24Larger office LAN (510 hosts)
/24255.255.255.00.0.0.2552562541 × /24Typical office LAN (old class C)
/25255.255.255.1280.0.0.1271281261/2 of a /24Smaller LAN or VLAN
/26255.255.255.1920.0.0.6364621/4 of a /24Smaller LAN or VLAN
/27255.255.255.2240.0.0.3132301/8 of a /24Small VLAN, phones, cameras
/28255.255.255.2400.0.0.1516141/16 of a /24Small VLAN, phones, cameras
/29255.255.255.2480.0.0.7861/32 of a /24Small fixed public block (5 usable)
/30255.255.255.2520.0.0.3421/64 of a /24Point-to-point (old style)
/31255.255.255.2540.0.0.1221/128 of a /24Point-to-point link (RFC 3021)
/32255.255.255.2550.0.0.0111/256 of a /24One host

IPv6 prefix reference

IPv6 prefix lengths
PrefixAddresses/64 LANs/48 sitesNibbleTypical use
/342,535,295,865,117,307,932,921,825,928,971,026,432 (2^125)2,305,843,009,213,693,95235,184,372,088,832NoAll global unicast (2000::/3)
/165,192,296,858,534,827,628,530,496,329,220,096 (2^112)281,474,976,710,6564,294,967,296Yes
/20324,518,553,658,426,726,783,156,020,576,256 (2^108)17,592,186,044,416268,435,456YesLarge provider allocation (RIPE minimum for some)
/29633,825,300,114,114,700,748,351,602,688 (2^99)34,359,738,368524,288NoRIPE allocation to a provider (often)
/3279,228,162,514,264,337,593,543,950,336 (2^96)4,294,967,29665,536YesProvider allocation (RIPE default)
/364,951,760,157,141,521,099,596,496,896 (2^92)268,435,4564,096Yes
/40309,485,009,821,345,068,724,781,056 (2^88)16,777,216256Yes
/4419,342,813,113,834,066,795,298,816 (2^84)1,048,57616Yes
/481,208,925,819,614,629,174,706,176 (2^80)65,5361YesOne site or organisation (RIPE PI / assignment)
/5275,557,863,725,914,323,419,136 (2^76)4,096Yes
/564,722,366,482,869,645,213,696 (2^72)256YesSmall site or home (common provider assignment)
/60295,147,905,179,352,825,856 (2^68)16YesSome home broadband (16 LANs)
/6418,446,744,073,709,551,616 (2^64)1YesOne LAN or VLAN (needed for SLAAC)
/7272,057,594,037,927,936 (2^56)1/256 of a /64Yes
/80281,474,976,710,656 (2^48)1/65,536 of a /64Yes
/964,294,967,2961/4,294,967,296 of a /64YesEmbeds an IPv4 address (NAT64)
/11265,5361/281,474,976,710,656 of a /64Yes
/1202561/72,057,594,037,927,936 of a /64Yes
/124161/1,152,921,504,606,846,976 of a /64Yes
/12641/4,611,686,018,427,387,904 of a /64No
/12721/9,223,372,036,854,775,808 of a /64NoPoint-to-point link (RFC 6164)
/12811/18,446,744,073,709,551,616 of a /64YesOne host or loopback

Private and special ranges

IPv4

Special-purpose ranges
RangeNameWhat it is
255.255.255.255/32Limited broadcastEvery host on the local network
0.0.0.0/8This networkNot routed; 0.0.0.0 means "any address" in settings
10.0.0.0/8Private (RFC 1918)Office and home networks; not routed on the internet
100.64.0.0/10Shared address space (CGNAT)Used by providers behind carrier-grade NAT (RFC 6598)
127.0.0.0/8LoopbackThis computer
169.254.0.0/16Link-local (APIPA)Self-assigned when no DHCP server answers
172.16.0.0/12Private (RFC 1918)Office and home networks; not routed on the internet
192.0.0.0/24IETF protocol assignmentsSpecial uses such as DS-Lite
192.0.2.0/24Documentation (TEST-NET-1)For examples; never used on a network
192.88.99.0/246to4 relay (deprecated)Formerly anycast for 6to4
192.168.0.0/16Private (RFC 1918)Office and home networks; not routed on the internet
198.18.0.0/15BenchmarkingNetwork equipment testing (RFC 2544)
198.51.100.0/24Documentation (TEST-NET-2)For examples; never used on a network
203.0.113.0/24Documentation (TEST-NET-3)For examples; never used on a network
224.0.0.0/4MulticastOne-to-many traffic, such as IPTV and routing protocols
240.0.0.0/4ReservedFuture use; not usable on most systems

IPv6

Special-purpose ranges
RangeNameWhat it is
::/128UnspecifiedNo address; :: means "any address" in settings
::1/128LoopbackThis computer
::ffff:0:0/96IPv4-mappedAn IPv4 address written as IPv6
64:ff9b::/96NAT64IPv4 addresses reached through a NAT64 gateway
100::/64Discard onlyTraffic sent here is dropped (RFC 6666)
2001:db8::/32DocumentationFor examples; never used on a network
2001::/32TeredoIPv6 tunnelled over IPv4 UDP
2002::/166to4IPv6 tunnelled over IPv4 (largely retired)
3fff::/20DocumentationFor examples (RFC 9637)
fc00::/7Unique local (ULA)Private IPv6, like RFC 1918; usually fd00::/8
fe80::/10Link-localEvery IPv6 interface has one; not routed
ff00::/8MulticastOne-to-many traffic; replaces broadcast
2000::/3Global unicastPublic internet addresses

About this tool

A network is written as an address and a prefix length, such as 192.168.1.0/24: the first 24 bits name the network and the rest number the devices on it. The calculator works out where the network starts and ends, how many devices it holds, its subnet and wildcard masks, and the reverse DNS zone to ask your provider for.

It also splits a network into equal smaller ones (one per VLAN or site), turns a range of addresses into the fewest CIDR blocks for a firewall rule, and lists every IPv4 prefix length and the common IPv6 ones in reference tables.

Common questions

Why are two addresses lost in every IPv4 subnet?

The first address names the network and the last is the broadcast address, so a /24 has 256 addresses but 254 for devices. A /31 (a link between two routers) and a /32 (one host) are the exceptions.

What size of IPv6 network should a LAN use?

Always /64. Devices pick their own address within it (SLAAC), which needs the full 64 bits. A site usually gets a /48 or /56 from its provider, which holds 65,536 or 256 LANs.

What is a wildcard mask?

The subnet mask turned inside out: 255.255.255.0 becomes 0.0.0.255. Cisco access lists and OSPF use it to say which bits must match.

Which ranges can I use inside an office?

IPv4: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. IPv6: unique local addresses from fd00::/8, though most networks use the public prefix from their provider.