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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.

Network91.78.2.0/23
Usable hosts510
Subnet mask255.255.254.0
Addresses512
Network address
91.78.2.0
Broadcast address
91.78.3.255
First usable
91.78.2.1
Last usable
91.78.3.254
Usable hosts
510 (512 less the network and broadcast addresses)
Subnet mask
255.255.254.0
Wildcard mask
0.0.1.255 (Cisco ACLs, OSPF)
Prefix length
/23
Type
Public public
Old class
A (default /8)
As numbers
Hex 5B4E0200 · Integer 1531838976 to 1531839487
Reverse DNS zones
2.78.91.in-addr.arpa
3.78.91.in-addr.arpa
/23 is not on a 8-bit boundary, so it takes 2 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01011011.01001110.00000010.0000000091.78.2.0
Subnet mask11111111.11111111.11111110.00000000255.255.254.0
Network01011011.01001110.00000010.0000000091.78.2.0
Broadcast01011011.01001110.00000011.1111111191.78.3.255
Split into smaller subnets/30
/24 (2)/25 (4)/26 (8)/27 (16)/28 (32)/29 (64)/30 (128)/31 (256)/32 (512)

91.78.2.0/23 makes 128 subnets of /30.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
191.78.2.0/3091.78.2.1 to 91.78.2.291.78.2.32
291.78.2.4/3091.78.2.5 to 91.78.2.691.78.2.72
391.78.2.8/3091.78.2.9 to 91.78.2.1091.78.2.112
491.78.2.12/3091.78.2.13 to 91.78.2.1491.78.2.152
591.78.2.16/3091.78.2.17 to 91.78.2.1891.78.2.192
691.78.2.20/3091.78.2.21 to 91.78.2.2291.78.2.232
791.78.2.24/3091.78.2.25 to 91.78.2.2691.78.2.272
891.78.2.28/3091.78.2.29 to 91.78.2.3091.78.2.312
991.78.2.32/3091.78.2.33 to 91.78.2.3491.78.2.352
1091.78.2.36/3091.78.2.37 to 91.78.2.3891.78.2.392
1191.78.2.40/3091.78.2.41 to 91.78.2.4291.78.2.432
1291.78.2.44/3091.78.2.45 to 91.78.2.4691.78.2.472
1391.78.2.48/3091.78.2.49 to 91.78.2.5091.78.2.512
1491.78.2.52/3091.78.2.53 to 91.78.2.5491.78.2.552
1591.78.2.56/3091.78.2.57 to 91.78.2.5891.78.2.592
1691.78.2.60/3091.78.2.61 to 91.78.2.6291.78.2.632
1791.78.2.64/3091.78.2.65 to 91.78.2.6691.78.2.672
1891.78.2.68/3091.78.2.69 to 91.78.2.7091.78.2.712
1991.78.2.72/3091.78.2.73 to 91.78.2.7491.78.2.752
2091.78.2.76/3091.78.2.77 to 91.78.2.7891.78.2.792
2191.78.2.80/3091.78.2.81 to 91.78.2.8291.78.2.832
2291.78.2.84/3091.78.2.85 to 91.78.2.8691.78.2.872
2391.78.2.88/3091.78.2.89 to 91.78.2.9091.78.2.912
2491.78.2.92/3091.78.2.93 to 91.78.2.9491.78.2.952
2591.78.2.96/3091.78.2.97 to 91.78.2.9891.78.2.992
2691.78.2.100/3091.78.2.101 to 91.78.2.10291.78.2.1032
2791.78.2.104/3091.78.2.105 to 91.78.2.10691.78.2.1072
2891.78.2.108/3091.78.2.109 to 91.78.2.11091.78.2.1112
2991.78.2.112/3091.78.2.113 to 91.78.2.11491.78.2.1152
3091.78.2.116/3091.78.2.117 to 91.78.2.11891.78.2.1192
3191.78.2.120/3091.78.2.121 to 91.78.2.12291.78.2.1232
3291.78.2.124/3091.78.2.125 to 91.78.2.12691.78.2.1272
3391.78.2.128/3091.78.2.129 to 91.78.2.13091.78.2.1312
3491.78.2.132/3091.78.2.133 to 91.78.2.13491.78.2.1352
3591.78.2.136/3091.78.2.137 to 91.78.2.13891.78.2.1392
3691.78.2.140/3091.78.2.141 to 91.78.2.14291.78.2.1432
3791.78.2.144/3091.78.2.145 to 91.78.2.14691.78.2.1472
3891.78.2.148/3091.78.2.149 to 91.78.2.15091.78.2.1512
3991.78.2.152/3091.78.2.153 to 91.78.2.15491.78.2.1552
4091.78.2.156/3091.78.2.157 to 91.78.2.15891.78.2.1592
4191.78.2.160/3091.78.2.161 to 91.78.2.16291.78.2.1632
4291.78.2.164/3091.78.2.165 to 91.78.2.16691.78.2.1672
4391.78.2.168/3091.78.2.169 to 91.78.2.17091.78.2.1712
4491.78.2.172/3091.78.2.173 to 91.78.2.17491.78.2.1752
4591.78.2.176/3091.78.2.177 to 91.78.2.17891.78.2.1792
4691.78.2.180/3091.78.2.181 to 91.78.2.18291.78.2.1832
4791.78.2.184/3091.78.2.185 to 91.78.2.18691.78.2.1872
4891.78.2.188/3091.78.2.189 to 91.78.2.19091.78.2.1912
4991.78.2.192/3091.78.2.193 to 91.78.2.19491.78.2.1952
5091.78.2.196/3091.78.2.197 to 91.78.2.19891.78.2.1992
5191.78.2.200/3091.78.2.201 to 91.78.2.20291.78.2.2032
5291.78.2.204/3091.78.2.205 to 91.78.2.20691.78.2.2072
5391.78.2.208/3091.78.2.209 to 91.78.2.21091.78.2.2112
5491.78.2.212/3091.78.2.213 to 91.78.2.21491.78.2.2152
5591.78.2.216/3091.78.2.217 to 91.78.2.21891.78.2.2192
5691.78.2.220/3091.78.2.221 to 91.78.2.22291.78.2.2232
5791.78.2.224/3091.78.2.225 to 91.78.2.22691.78.2.2272
5891.78.2.228/3091.78.2.229 to 91.78.2.23091.78.2.2312
5991.78.2.232/3091.78.2.233 to 91.78.2.23491.78.2.2352
6091.78.2.236/3091.78.2.237 to 91.78.2.23891.78.2.2392
6191.78.2.240/3091.78.2.241 to 91.78.2.24291.78.2.2432
6291.78.2.244/3091.78.2.245 to 91.78.2.24691.78.2.2472
6391.78.2.248/3091.78.2.249 to 91.78.2.25091.78.2.2512
6491.78.2.252/3091.78.2.253 to 91.78.2.25491.78.2.2552
6591.78.3.0/3091.78.3.1 to 91.78.3.291.78.3.32
6691.78.3.4/3091.78.3.5 to 91.78.3.691.78.3.72
6791.78.3.8/3091.78.3.9 to 91.78.3.1091.78.3.112
6891.78.3.12/3091.78.3.13 to 91.78.3.1491.78.3.152
6991.78.3.16/3091.78.3.17 to 91.78.3.1891.78.3.192
7091.78.3.20/3091.78.3.21 to 91.78.3.2291.78.3.232
7191.78.3.24/3091.78.3.25 to 91.78.3.2691.78.3.272
7291.78.3.28/3091.78.3.29 to 91.78.3.3091.78.3.312
7391.78.3.32/3091.78.3.33 to 91.78.3.3491.78.3.352
7491.78.3.36/3091.78.3.37 to 91.78.3.3891.78.3.392
7591.78.3.40/3091.78.3.41 to 91.78.3.4291.78.3.432
7691.78.3.44/3091.78.3.45 to 91.78.3.4691.78.3.472
7791.78.3.48/3091.78.3.49 to 91.78.3.5091.78.3.512
7891.78.3.52/3091.78.3.53 to 91.78.3.5491.78.3.552
7991.78.3.56/3091.78.3.57 to 91.78.3.5891.78.3.592
8091.78.3.60/3091.78.3.61 to 91.78.3.6291.78.3.632
8191.78.3.64/3091.78.3.65 to 91.78.3.6691.78.3.672
8291.78.3.68/3091.78.3.69 to 91.78.3.7091.78.3.712
8391.78.3.72/3091.78.3.73 to 91.78.3.7491.78.3.752
8491.78.3.76/3091.78.3.77 to 91.78.3.7891.78.3.792
8591.78.3.80/3091.78.3.81 to 91.78.3.8291.78.3.832
8691.78.3.84/3091.78.3.85 to 91.78.3.8691.78.3.872
8791.78.3.88/3091.78.3.89 to 91.78.3.9091.78.3.912
8891.78.3.92/3091.78.3.93 to 91.78.3.9491.78.3.952
8991.78.3.96/3091.78.3.97 to 91.78.3.9891.78.3.992
9091.78.3.100/3091.78.3.101 to 91.78.3.10291.78.3.1032
9191.78.3.104/3091.78.3.105 to 91.78.3.10691.78.3.1072
9291.78.3.108/3091.78.3.109 to 91.78.3.11091.78.3.1112
9391.78.3.112/3091.78.3.113 to 91.78.3.11491.78.3.1152
9491.78.3.116/3091.78.3.117 to 91.78.3.11891.78.3.1192
9591.78.3.120/3091.78.3.121 to 91.78.3.12291.78.3.1232
9691.78.3.124/3091.78.3.125 to 91.78.3.12691.78.3.1272
9791.78.3.128/3091.78.3.129 to 91.78.3.13091.78.3.1312
9891.78.3.132/3091.78.3.133 to 91.78.3.13491.78.3.1352
9991.78.3.136/3091.78.3.137 to 91.78.3.13891.78.3.1392
10091.78.3.140/3091.78.3.141 to 91.78.3.14291.78.3.1432
10191.78.3.144/3091.78.3.145 to 91.78.3.14691.78.3.1472
10291.78.3.148/3091.78.3.149 to 91.78.3.15091.78.3.1512
10391.78.3.152/3091.78.3.153 to 91.78.3.15491.78.3.1552
10491.78.3.156/3091.78.3.157 to 91.78.3.15891.78.3.1592
10591.78.3.160/3091.78.3.161 to 91.78.3.16291.78.3.1632
10691.78.3.164/3091.78.3.165 to 91.78.3.16691.78.3.1672
10791.78.3.168/3091.78.3.169 to 91.78.3.17091.78.3.1712
10891.78.3.172/3091.78.3.173 to 91.78.3.17491.78.3.1752
10991.78.3.176/3091.78.3.177 to 91.78.3.17891.78.3.1792
11091.78.3.180/3091.78.3.181 to 91.78.3.18291.78.3.1832
11191.78.3.184/3091.78.3.185 to 91.78.3.18691.78.3.1872
11291.78.3.188/3091.78.3.189 to 91.78.3.19091.78.3.1912
11391.78.3.192/3091.78.3.193 to 91.78.3.19491.78.3.1952
11491.78.3.196/3091.78.3.197 to 91.78.3.19891.78.3.1992
11591.78.3.200/3091.78.3.201 to 91.78.3.20291.78.3.2032
11691.78.3.204/3091.78.3.205 to 91.78.3.20691.78.3.2072
11791.78.3.208/3091.78.3.209 to 91.78.3.21091.78.3.2112
11891.78.3.212/3091.78.3.213 to 91.78.3.21491.78.3.2152
11991.78.3.216/3091.78.3.217 to 91.78.3.21891.78.3.2192
12091.78.3.220/3091.78.3.221 to 91.78.3.22291.78.3.2232
12191.78.3.224/3091.78.3.225 to 91.78.3.22691.78.3.2272
12291.78.3.228/3091.78.3.229 to 91.78.3.23091.78.3.2312
12391.78.3.232/3091.78.3.233 to 91.78.3.23491.78.3.2352
12491.78.3.236/3091.78.3.237 to 91.78.3.23891.78.3.2392
12591.78.3.240/3091.78.3.241 to 91.78.3.24291.78.3.2432
12691.78.3.244/3091.78.3.245 to 91.78.3.24691.78.3.2472
12791.78.3.248/3091.78.3.249 to 91.78.3.25091.78.3.2512
12891.78.3.252/3091.78.3.253 to 91.78.3.25491.78.3.2552

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.