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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.

Network91.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
91.0.0.0
Broadcast address
91.255.255.255
First usable
91.0.0.1
Last usable
91.255.255.254
Usable hosts
16,777,214 (16,777,216 less the network and broadcast addresses)
Subnet mask
255.0.0.0
Wildcard mask
0.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/8
Type
Public public
Old class
A (default /8)
As numbers
Hex 5B000000 · Integer 1526726656 to 1543503871
Reverse DNS zone
91.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01011011..00000000.00000000.0000000091.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network01011011..00000000.00000000.0000000091.0.0.0
Broadcast01011011..11111111.11111111.1111111191.255.255.255
Split into smaller subnets/14
/9 (2)/10 (4)/11 (8)/12 (16)/13 (32)/14 (64)/15 (128)/16 (256)/17 (512)/18 (1,024)/19 (2,048)/20 (4,096)

91.0.0.0/8 makes 64 subnets of /14.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
191.0.0.0/1491.0.0.1 to 91.3.255.25491.3.255.255262,142
291.4.0.0/1491.4.0.1 to 91.7.255.25491.7.255.255262,142
391.8.0.0/1491.8.0.1 to 91.11.255.25491.11.255.255262,142
491.12.0.0/1491.12.0.1 to 91.15.255.25491.15.255.255262,142
591.16.0.0/1491.16.0.1 to 91.19.255.25491.19.255.255262,142
691.20.0.0/1491.20.0.1 to 91.23.255.25491.23.255.255262,142
791.24.0.0/1491.24.0.1 to 91.27.255.25491.27.255.255262,142
891.28.0.0/1491.28.0.1 to 91.31.255.25491.31.255.255262,142
991.32.0.0/1491.32.0.1 to 91.35.255.25491.35.255.255262,142
1091.36.0.0/1491.36.0.1 to 91.39.255.25491.39.255.255262,142
1191.40.0.0/1491.40.0.1 to 91.43.255.25491.43.255.255262,142
1291.44.0.0/1491.44.0.1 to 91.47.255.25491.47.255.255262,142
1391.48.0.0/1491.48.0.1 to 91.51.255.25491.51.255.255262,142
1491.52.0.0/1491.52.0.1 to 91.55.255.25491.55.255.255262,142
1591.56.0.0/1491.56.0.1 to 91.59.255.25491.59.255.255262,142
1691.60.0.0/1491.60.0.1 to 91.63.255.25491.63.255.255262,142
1791.64.0.0/1491.64.0.1 to 91.67.255.25491.67.255.255262,142
1891.68.0.0/1491.68.0.1 to 91.71.255.25491.71.255.255262,142
1991.72.0.0/1491.72.0.1 to 91.75.255.25491.75.255.255262,142
2091.76.0.0/1491.76.0.1 to 91.79.255.25491.79.255.255262,142
2191.80.0.0/1491.80.0.1 to 91.83.255.25491.83.255.255262,142
2291.84.0.0/1491.84.0.1 to 91.87.255.25491.87.255.255262,142
2391.88.0.0/1491.88.0.1 to 91.91.255.25491.91.255.255262,142
2491.92.0.0/1491.92.0.1 to 91.95.255.25491.95.255.255262,142
2591.96.0.0/1491.96.0.1 to 91.99.255.25491.99.255.255262,142
2691.100.0.0/1491.100.0.1 to 91.103.255.25491.103.255.255262,142
2791.104.0.0/1491.104.0.1 to 91.107.255.25491.107.255.255262,142
2891.108.0.0/1491.108.0.1 to 91.111.255.25491.111.255.255262,142
2991.112.0.0/1491.112.0.1 to 91.115.255.25491.115.255.255262,142
3091.116.0.0/1491.116.0.1 to 91.119.255.25491.119.255.255262,142
3191.120.0.0/1491.120.0.1 to 91.123.255.25491.123.255.255262,142
3291.124.0.0/1491.124.0.1 to 91.127.255.25491.127.255.255262,142
3391.128.0.0/1491.128.0.1 to 91.131.255.25491.131.255.255262,142
3491.132.0.0/1491.132.0.1 to 91.135.255.25491.135.255.255262,142
3591.136.0.0/1491.136.0.1 to 91.139.255.25491.139.255.255262,142
3691.140.0.0/1491.140.0.1 to 91.143.255.25491.143.255.255262,142
3791.144.0.0/1491.144.0.1 to 91.147.255.25491.147.255.255262,142
3891.148.0.0/1491.148.0.1 to 91.151.255.25491.151.255.255262,142
3991.152.0.0/1491.152.0.1 to 91.155.255.25491.155.255.255262,142
4091.156.0.0/1491.156.0.1 to 91.159.255.25491.159.255.255262,142
4191.160.0.0/1491.160.0.1 to 91.163.255.25491.163.255.255262,142
4291.164.0.0/1491.164.0.1 to 91.167.255.25491.167.255.255262,142
4391.168.0.0/1491.168.0.1 to 91.171.255.25491.171.255.255262,142
4491.172.0.0/1491.172.0.1 to 91.175.255.25491.175.255.255262,142
4591.176.0.0/1491.176.0.1 to 91.179.255.25491.179.255.255262,142
4691.180.0.0/1491.180.0.1 to 91.183.255.25491.183.255.255262,142
4791.184.0.0/1491.184.0.1 to 91.187.255.25491.187.255.255262,142
4891.188.0.0/1491.188.0.1 to 91.191.255.25491.191.255.255262,142
4991.192.0.0/1491.192.0.1 to 91.195.255.25491.195.255.255262,142
5091.196.0.0/1491.196.0.1 to 91.199.255.25491.199.255.255262,142
5191.200.0.0/1491.200.0.1 to 91.203.255.25491.203.255.255262,142
5291.204.0.0/1491.204.0.1 to 91.207.255.25491.207.255.255262,142
5391.208.0.0/1491.208.0.1 to 91.211.255.25491.211.255.255262,142
5491.212.0.0/1491.212.0.1 to 91.215.255.25491.215.255.255262,142
5591.216.0.0/1491.216.0.1 to 91.219.255.25491.219.255.255262,142
5691.220.0.0/1491.220.0.1 to 91.223.255.25491.223.255.255262,142
5791.224.0.0/1491.224.0.1 to 91.227.255.25491.227.255.255262,142
5891.228.0.0/1491.228.0.1 to 91.231.255.25491.231.255.255262,142
5991.232.0.0/1491.232.0.1 to 91.235.255.25491.235.255.255262,142
6091.236.0.0/1491.236.0.1 to 91.239.255.25491.239.255.255262,142
6191.240.0.0/1491.240.0.1 to 91.243.255.25491.243.255.255262,142
6291.244.0.0/1491.244.0.1 to 91.247.255.25491.247.255.255262,142
6391.248.0.0/1491.248.0.1 to 91.251.255.25491.251.255.255262,142
6491.252.0.0/1491.252.0.1 to 91.255.255.25491.255.255.255262,142

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.