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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.

Network255.0.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
255.0.0.0
Broadcast address
255.1.255.255
First usable
255.0.0.1
Last usable
255.1.255.254
Usable hosts
131,070 (131,072 less the network and broadcast addresses)
Subnet mask
255.254.0.0
Wildcard mask
0.1.255.255 (Cisco ACLs, OSPF)
Prefix length
/15
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex FF000000 · Integer 4278190080 to 4278321151
Reverse DNS zones
0.255.in-addr.arpa
1.255.in-addr.arpa
/15 is not on a 8-bit boundary, so it takes 2 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11111111.00000000.00000000.00000000255.0.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network11111111.00000000.00000000.00000000255.0.0.0
Broadcast11111111.00000001.11111111.11111111255.1.255.255
Split into smaller subnets/22
/16 (2)/17 (4)/18 (8)/19 (16)/20 (32)/21 (64)/22 (128)/23 (256)/24 (512)/25 (1,024)/26 (2,048)/27 (4,096)

255.0.0.0/15 makes 128 subnets of /22.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1255.0.0.0/22255.0.0.1 to 255.0.3.254255.0.3.2551,022
2255.0.4.0/22255.0.4.1 to 255.0.7.254255.0.7.2551,022
3255.0.8.0/22255.0.8.1 to 255.0.11.254255.0.11.2551,022
4255.0.12.0/22255.0.12.1 to 255.0.15.254255.0.15.2551,022
5255.0.16.0/22255.0.16.1 to 255.0.19.254255.0.19.2551,022
6255.0.20.0/22255.0.20.1 to 255.0.23.254255.0.23.2551,022
7255.0.24.0/22255.0.24.1 to 255.0.27.254255.0.27.2551,022
8255.0.28.0/22255.0.28.1 to 255.0.31.254255.0.31.2551,022
9255.0.32.0/22255.0.32.1 to 255.0.35.254255.0.35.2551,022
10255.0.36.0/22255.0.36.1 to 255.0.39.254255.0.39.2551,022
11255.0.40.0/22255.0.40.1 to 255.0.43.254255.0.43.2551,022
12255.0.44.0/22255.0.44.1 to 255.0.47.254255.0.47.2551,022
13255.0.48.0/22255.0.48.1 to 255.0.51.254255.0.51.2551,022
14255.0.52.0/22255.0.52.1 to 255.0.55.254255.0.55.2551,022
15255.0.56.0/22255.0.56.1 to 255.0.59.254255.0.59.2551,022
16255.0.60.0/22255.0.60.1 to 255.0.63.254255.0.63.2551,022
17255.0.64.0/22255.0.64.1 to 255.0.67.254255.0.67.2551,022
18255.0.68.0/22255.0.68.1 to 255.0.71.254255.0.71.2551,022
19255.0.72.0/22255.0.72.1 to 255.0.75.254255.0.75.2551,022
20255.0.76.0/22255.0.76.1 to 255.0.79.254255.0.79.2551,022
21255.0.80.0/22255.0.80.1 to 255.0.83.254255.0.83.2551,022
22255.0.84.0/22255.0.84.1 to 255.0.87.254255.0.87.2551,022
23255.0.88.0/22255.0.88.1 to 255.0.91.254255.0.91.2551,022
24255.0.92.0/22255.0.92.1 to 255.0.95.254255.0.95.2551,022
25255.0.96.0/22255.0.96.1 to 255.0.99.254255.0.99.2551,022
26255.0.100.0/22255.0.100.1 to 255.0.103.254255.0.103.2551,022
27255.0.104.0/22255.0.104.1 to 255.0.107.254255.0.107.2551,022
28255.0.108.0/22255.0.108.1 to 255.0.111.254255.0.111.2551,022
29255.0.112.0/22255.0.112.1 to 255.0.115.254255.0.115.2551,022
30255.0.116.0/22255.0.116.1 to 255.0.119.254255.0.119.2551,022
31255.0.120.0/22255.0.120.1 to 255.0.123.254255.0.123.2551,022
32255.0.124.0/22255.0.124.1 to 255.0.127.254255.0.127.2551,022
33255.0.128.0/22255.0.128.1 to 255.0.131.254255.0.131.2551,022
34255.0.132.0/22255.0.132.1 to 255.0.135.254255.0.135.2551,022
35255.0.136.0/22255.0.136.1 to 255.0.139.254255.0.139.2551,022
36255.0.140.0/22255.0.140.1 to 255.0.143.254255.0.143.2551,022
37255.0.144.0/22255.0.144.1 to 255.0.147.254255.0.147.2551,022
38255.0.148.0/22255.0.148.1 to 255.0.151.254255.0.151.2551,022
39255.0.152.0/22255.0.152.1 to 255.0.155.254255.0.155.2551,022
40255.0.156.0/22255.0.156.1 to 255.0.159.254255.0.159.2551,022
41255.0.160.0/22255.0.160.1 to 255.0.163.254255.0.163.2551,022
42255.0.164.0/22255.0.164.1 to 255.0.167.254255.0.167.2551,022
43255.0.168.0/22255.0.168.1 to 255.0.171.254255.0.171.2551,022
44255.0.172.0/22255.0.172.1 to 255.0.175.254255.0.175.2551,022
45255.0.176.0/22255.0.176.1 to 255.0.179.254255.0.179.2551,022
46255.0.180.0/22255.0.180.1 to 255.0.183.254255.0.183.2551,022
47255.0.184.0/22255.0.184.1 to 255.0.187.254255.0.187.2551,022
48255.0.188.0/22255.0.188.1 to 255.0.191.254255.0.191.2551,022
49255.0.192.0/22255.0.192.1 to 255.0.195.254255.0.195.2551,022
50255.0.196.0/22255.0.196.1 to 255.0.199.254255.0.199.2551,022
51255.0.200.0/22255.0.200.1 to 255.0.203.254255.0.203.2551,022
52255.0.204.0/22255.0.204.1 to 255.0.207.254255.0.207.2551,022
53255.0.208.0/22255.0.208.1 to 255.0.211.254255.0.211.2551,022
54255.0.212.0/22255.0.212.1 to 255.0.215.254255.0.215.2551,022
55255.0.216.0/22255.0.216.1 to 255.0.219.254255.0.219.2551,022
56255.0.220.0/22255.0.220.1 to 255.0.223.254255.0.223.2551,022
57255.0.224.0/22255.0.224.1 to 255.0.227.254255.0.227.2551,022
58255.0.228.0/22255.0.228.1 to 255.0.231.254255.0.231.2551,022
59255.0.232.0/22255.0.232.1 to 255.0.235.254255.0.235.2551,022
60255.0.236.0/22255.0.236.1 to 255.0.239.254255.0.239.2551,022
61255.0.240.0/22255.0.240.1 to 255.0.243.254255.0.243.2551,022
62255.0.244.0/22255.0.244.1 to 255.0.247.254255.0.247.2551,022
63255.0.248.0/22255.0.248.1 to 255.0.251.254255.0.251.2551,022
64255.0.252.0/22255.0.252.1 to 255.0.255.254255.0.255.2551,022
65255.1.0.0/22255.1.0.1 to 255.1.3.254255.1.3.2551,022
66255.1.4.0/22255.1.4.1 to 255.1.7.254255.1.7.2551,022
67255.1.8.0/22255.1.8.1 to 255.1.11.254255.1.11.2551,022
68255.1.12.0/22255.1.12.1 to 255.1.15.254255.1.15.2551,022
69255.1.16.0/22255.1.16.1 to 255.1.19.254255.1.19.2551,022
70255.1.20.0/22255.1.20.1 to 255.1.23.254255.1.23.2551,022
71255.1.24.0/22255.1.24.1 to 255.1.27.254255.1.27.2551,022
72255.1.28.0/22255.1.28.1 to 255.1.31.254255.1.31.2551,022
73255.1.32.0/22255.1.32.1 to 255.1.35.254255.1.35.2551,022
74255.1.36.0/22255.1.36.1 to 255.1.39.254255.1.39.2551,022
75255.1.40.0/22255.1.40.1 to 255.1.43.254255.1.43.2551,022
76255.1.44.0/22255.1.44.1 to 255.1.47.254255.1.47.2551,022
77255.1.48.0/22255.1.48.1 to 255.1.51.254255.1.51.2551,022
78255.1.52.0/22255.1.52.1 to 255.1.55.254255.1.55.2551,022
79255.1.56.0/22255.1.56.1 to 255.1.59.254255.1.59.2551,022
80255.1.60.0/22255.1.60.1 to 255.1.63.254255.1.63.2551,022
81255.1.64.0/22255.1.64.1 to 255.1.67.254255.1.67.2551,022
82255.1.68.0/22255.1.68.1 to 255.1.71.254255.1.71.2551,022
83255.1.72.0/22255.1.72.1 to 255.1.75.254255.1.75.2551,022
84255.1.76.0/22255.1.76.1 to 255.1.79.254255.1.79.2551,022
85255.1.80.0/22255.1.80.1 to 255.1.83.254255.1.83.2551,022
86255.1.84.0/22255.1.84.1 to 255.1.87.254255.1.87.2551,022
87255.1.88.0/22255.1.88.1 to 255.1.91.254255.1.91.2551,022
88255.1.92.0/22255.1.92.1 to 255.1.95.254255.1.95.2551,022
89255.1.96.0/22255.1.96.1 to 255.1.99.254255.1.99.2551,022
90255.1.100.0/22255.1.100.1 to 255.1.103.254255.1.103.2551,022
91255.1.104.0/22255.1.104.1 to 255.1.107.254255.1.107.2551,022
92255.1.108.0/22255.1.108.1 to 255.1.111.254255.1.111.2551,022
93255.1.112.0/22255.1.112.1 to 255.1.115.254255.1.115.2551,022
94255.1.116.0/22255.1.116.1 to 255.1.119.254255.1.119.2551,022
95255.1.120.0/22255.1.120.1 to 255.1.123.254255.1.123.2551,022
96255.1.124.0/22255.1.124.1 to 255.1.127.254255.1.127.2551,022
97255.1.128.0/22255.1.128.1 to 255.1.131.254255.1.131.2551,022
98255.1.132.0/22255.1.132.1 to 255.1.135.254255.1.135.2551,022
99255.1.136.0/22255.1.136.1 to 255.1.139.254255.1.139.2551,022
100255.1.140.0/22255.1.140.1 to 255.1.143.254255.1.143.2551,022
101255.1.144.0/22255.1.144.1 to 255.1.147.254255.1.147.2551,022
102255.1.148.0/22255.1.148.1 to 255.1.151.254255.1.151.2551,022
103255.1.152.0/22255.1.152.1 to 255.1.155.254255.1.155.2551,022
104255.1.156.0/22255.1.156.1 to 255.1.159.254255.1.159.2551,022
105255.1.160.0/22255.1.160.1 to 255.1.163.254255.1.163.2551,022
106255.1.164.0/22255.1.164.1 to 255.1.167.254255.1.167.2551,022
107255.1.168.0/22255.1.168.1 to 255.1.171.254255.1.171.2551,022
108255.1.172.0/22255.1.172.1 to 255.1.175.254255.1.175.2551,022
109255.1.176.0/22255.1.176.1 to 255.1.179.254255.1.179.2551,022
110255.1.180.0/22255.1.180.1 to 255.1.183.254255.1.183.2551,022
111255.1.184.0/22255.1.184.1 to 255.1.187.254255.1.187.2551,022
112255.1.188.0/22255.1.188.1 to 255.1.191.254255.1.191.2551,022
113255.1.192.0/22255.1.192.1 to 255.1.195.254255.1.195.2551,022
114255.1.196.0/22255.1.196.1 to 255.1.199.254255.1.199.2551,022
115255.1.200.0/22255.1.200.1 to 255.1.203.254255.1.203.2551,022
116255.1.204.0/22255.1.204.1 to 255.1.207.254255.1.207.2551,022
117255.1.208.0/22255.1.208.1 to 255.1.211.254255.1.211.2551,022
118255.1.212.0/22255.1.212.1 to 255.1.215.254255.1.215.2551,022
119255.1.216.0/22255.1.216.1 to 255.1.219.254255.1.219.2551,022
120255.1.220.0/22255.1.220.1 to 255.1.223.254255.1.223.2551,022
121255.1.224.0/22255.1.224.1 to 255.1.227.254255.1.227.2551,022
122255.1.228.0/22255.1.228.1 to 255.1.231.254255.1.231.2551,022
123255.1.232.0/22255.1.232.1 to 255.1.235.254255.1.235.2551,022
124255.1.236.0/22255.1.236.1 to 255.1.239.254255.1.239.2551,022
125255.1.240.0/22255.1.240.1 to 255.1.243.254255.1.243.2551,022
126255.1.244.0/22255.1.244.1 to 255.1.247.254255.1.247.2551,022
127255.1.248.0/22255.1.248.1 to 255.1.251.254255.1.251.2551,022
128255.1.252.0/22255.1.252.1 to 255.1.255.254255.1.255.2551,022

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.