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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.

Network191.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
191.0.0.0
Broadcast address
191.127.255.255
First usable
191.0.0.1
Last usable
191.127.255.254
Usable hosts
8,388,606 (8,388,608 less the network and broadcast addresses)
Subnet mask
255.128.0.0
Wildcard mask
0.127.255.255 (Cisco ACLs, OSPF)
Prefix length
/9
Type
Public public
Old class
B (default /16)
As numbers
Hex BF000000 · Integer 3204448256 to 3212836863
Reverse DNS zones
0.191.in-addr.arpa
1.191.in-addr.arpa
2.191.in-addr.arpa
3.191.in-addr.arpa
4.191.in-addr.arpa
5.191.in-addr.arpa
6.191.in-addr.arpa
7.191.in-addr.arpa
8.191.in-addr.arpa
9.191.in-addr.arpa
10.191.in-addr.arpa
11.191.in-addr.arpa
12.191.in-addr.arpa
13.191.in-addr.arpa
14.191.in-addr.arpa
15.191.in-addr.arpa
and 112 more
/9 is not on a 8-bit boundary, so it takes 128 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10111111.00000000.00000000.00000000191.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network10111111.00000000.00000000.00000000191.0.0.0
Broadcast10111111.01111111.11111111.11111111191.127.255.255
Split into smaller subnets/16
/10 (2)/11 (4)/12 (8)/13 (16)/14 (32)/15 (64)/16 (128)/17 (256)/18 (512)/19 (1,024)/20 (2,048)/21 (4,096)

191.0.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1191.0.0.0/16191.0.0.1 to 191.0.255.254191.0.255.25565,534
2191.1.0.0/16191.1.0.1 to 191.1.255.254191.1.255.25565,534
3191.2.0.0/16191.2.0.1 to 191.2.255.254191.2.255.25565,534
4191.3.0.0/16191.3.0.1 to 191.3.255.254191.3.255.25565,534
5191.4.0.0/16191.4.0.1 to 191.4.255.254191.4.255.25565,534
6191.5.0.0/16191.5.0.1 to 191.5.255.254191.5.255.25565,534
7191.6.0.0/16191.6.0.1 to 191.6.255.254191.6.255.25565,534
8191.7.0.0/16191.7.0.1 to 191.7.255.254191.7.255.25565,534
9191.8.0.0/16191.8.0.1 to 191.8.255.254191.8.255.25565,534
10191.9.0.0/16191.9.0.1 to 191.9.255.254191.9.255.25565,534
11191.10.0.0/16191.10.0.1 to 191.10.255.254191.10.255.25565,534
12191.11.0.0/16191.11.0.1 to 191.11.255.254191.11.255.25565,534
13191.12.0.0/16191.12.0.1 to 191.12.255.254191.12.255.25565,534
14191.13.0.0/16191.13.0.1 to 191.13.255.254191.13.255.25565,534
15191.14.0.0/16191.14.0.1 to 191.14.255.254191.14.255.25565,534
16191.15.0.0/16191.15.0.1 to 191.15.255.254191.15.255.25565,534
17191.16.0.0/16191.16.0.1 to 191.16.255.254191.16.255.25565,534
18191.17.0.0/16191.17.0.1 to 191.17.255.254191.17.255.25565,534
19191.18.0.0/16191.18.0.1 to 191.18.255.254191.18.255.25565,534
20191.19.0.0/16191.19.0.1 to 191.19.255.254191.19.255.25565,534
21191.20.0.0/16191.20.0.1 to 191.20.255.254191.20.255.25565,534
22191.21.0.0/16191.21.0.1 to 191.21.255.254191.21.255.25565,534
23191.22.0.0/16191.22.0.1 to 191.22.255.254191.22.255.25565,534
24191.23.0.0/16191.23.0.1 to 191.23.255.254191.23.255.25565,534
25191.24.0.0/16191.24.0.1 to 191.24.255.254191.24.255.25565,534
26191.25.0.0/16191.25.0.1 to 191.25.255.254191.25.255.25565,534
27191.26.0.0/16191.26.0.1 to 191.26.255.254191.26.255.25565,534
28191.27.0.0/16191.27.0.1 to 191.27.255.254191.27.255.25565,534
29191.28.0.0/16191.28.0.1 to 191.28.255.254191.28.255.25565,534
30191.29.0.0/16191.29.0.1 to 191.29.255.254191.29.255.25565,534
31191.30.0.0/16191.30.0.1 to 191.30.255.254191.30.255.25565,534
32191.31.0.0/16191.31.0.1 to 191.31.255.254191.31.255.25565,534
33191.32.0.0/16191.32.0.1 to 191.32.255.254191.32.255.25565,534
34191.33.0.0/16191.33.0.1 to 191.33.255.254191.33.255.25565,534
35191.34.0.0/16191.34.0.1 to 191.34.255.254191.34.255.25565,534
36191.35.0.0/16191.35.0.1 to 191.35.255.254191.35.255.25565,534
37191.36.0.0/16191.36.0.1 to 191.36.255.254191.36.255.25565,534
38191.37.0.0/16191.37.0.1 to 191.37.255.254191.37.255.25565,534
39191.38.0.0/16191.38.0.1 to 191.38.255.254191.38.255.25565,534
40191.39.0.0/16191.39.0.1 to 191.39.255.254191.39.255.25565,534
41191.40.0.0/16191.40.0.1 to 191.40.255.254191.40.255.25565,534
42191.41.0.0/16191.41.0.1 to 191.41.255.254191.41.255.25565,534
43191.42.0.0/16191.42.0.1 to 191.42.255.254191.42.255.25565,534
44191.43.0.0/16191.43.0.1 to 191.43.255.254191.43.255.25565,534
45191.44.0.0/16191.44.0.1 to 191.44.255.254191.44.255.25565,534
46191.45.0.0/16191.45.0.1 to 191.45.255.254191.45.255.25565,534
47191.46.0.0/16191.46.0.1 to 191.46.255.254191.46.255.25565,534
48191.47.0.0/16191.47.0.1 to 191.47.255.254191.47.255.25565,534
49191.48.0.0/16191.48.0.1 to 191.48.255.254191.48.255.25565,534
50191.49.0.0/16191.49.0.1 to 191.49.255.254191.49.255.25565,534
51191.50.0.0/16191.50.0.1 to 191.50.255.254191.50.255.25565,534
52191.51.0.0/16191.51.0.1 to 191.51.255.254191.51.255.25565,534
53191.52.0.0/16191.52.0.1 to 191.52.255.254191.52.255.25565,534
54191.53.0.0/16191.53.0.1 to 191.53.255.254191.53.255.25565,534
55191.54.0.0/16191.54.0.1 to 191.54.255.254191.54.255.25565,534
56191.55.0.0/16191.55.0.1 to 191.55.255.254191.55.255.25565,534
57191.56.0.0/16191.56.0.1 to 191.56.255.254191.56.255.25565,534
58191.57.0.0/16191.57.0.1 to 191.57.255.254191.57.255.25565,534
59191.58.0.0/16191.58.0.1 to 191.58.255.254191.58.255.25565,534
60191.59.0.0/16191.59.0.1 to 191.59.255.254191.59.255.25565,534
61191.60.0.0/16191.60.0.1 to 191.60.255.254191.60.255.25565,534
62191.61.0.0/16191.61.0.1 to 191.61.255.254191.61.255.25565,534
63191.62.0.0/16191.62.0.1 to 191.62.255.254191.62.255.25565,534
64191.63.0.0/16191.63.0.1 to 191.63.255.254191.63.255.25565,534
65191.64.0.0/16191.64.0.1 to 191.64.255.254191.64.255.25565,534
66191.65.0.0/16191.65.0.1 to 191.65.255.254191.65.255.25565,534
67191.66.0.0/16191.66.0.1 to 191.66.255.254191.66.255.25565,534
68191.67.0.0/16191.67.0.1 to 191.67.255.254191.67.255.25565,534
69191.68.0.0/16191.68.0.1 to 191.68.255.254191.68.255.25565,534
70191.69.0.0/16191.69.0.1 to 191.69.255.254191.69.255.25565,534
71191.70.0.0/16191.70.0.1 to 191.70.255.254191.70.255.25565,534
72191.71.0.0/16191.71.0.1 to 191.71.255.254191.71.255.25565,534
73191.72.0.0/16191.72.0.1 to 191.72.255.254191.72.255.25565,534
74191.73.0.0/16191.73.0.1 to 191.73.255.254191.73.255.25565,534
75191.74.0.0/16191.74.0.1 to 191.74.255.254191.74.255.25565,534
76191.75.0.0/16191.75.0.1 to 191.75.255.254191.75.255.25565,534
77191.76.0.0/16191.76.0.1 to 191.76.255.254191.76.255.25565,534
78191.77.0.0/16191.77.0.1 to 191.77.255.254191.77.255.25565,534
79191.78.0.0/16191.78.0.1 to 191.78.255.254191.78.255.25565,534
80191.79.0.0/16191.79.0.1 to 191.79.255.254191.79.255.25565,534
81191.80.0.0/16191.80.0.1 to 191.80.255.254191.80.255.25565,534
82191.81.0.0/16191.81.0.1 to 191.81.255.254191.81.255.25565,534
83191.82.0.0/16191.82.0.1 to 191.82.255.254191.82.255.25565,534
84191.83.0.0/16191.83.0.1 to 191.83.255.254191.83.255.25565,534
85191.84.0.0/16191.84.0.1 to 191.84.255.254191.84.255.25565,534
86191.85.0.0/16191.85.0.1 to 191.85.255.254191.85.255.25565,534
87191.86.0.0/16191.86.0.1 to 191.86.255.254191.86.255.25565,534
88191.87.0.0/16191.87.0.1 to 191.87.255.254191.87.255.25565,534
89191.88.0.0/16191.88.0.1 to 191.88.255.254191.88.255.25565,534
90191.89.0.0/16191.89.0.1 to 191.89.255.254191.89.255.25565,534
91191.90.0.0/16191.90.0.1 to 191.90.255.254191.90.255.25565,534
92191.91.0.0/16191.91.0.1 to 191.91.255.254191.91.255.25565,534
93191.92.0.0/16191.92.0.1 to 191.92.255.254191.92.255.25565,534
94191.93.0.0/16191.93.0.1 to 191.93.255.254191.93.255.25565,534
95191.94.0.0/16191.94.0.1 to 191.94.255.254191.94.255.25565,534
96191.95.0.0/16191.95.0.1 to 191.95.255.254191.95.255.25565,534
97191.96.0.0/16191.96.0.1 to 191.96.255.254191.96.255.25565,534
98191.97.0.0/16191.97.0.1 to 191.97.255.254191.97.255.25565,534
99191.98.0.0/16191.98.0.1 to 191.98.255.254191.98.255.25565,534
100191.99.0.0/16191.99.0.1 to 191.99.255.254191.99.255.25565,534
101191.100.0.0/16191.100.0.1 to 191.100.255.254191.100.255.25565,534
102191.101.0.0/16191.101.0.1 to 191.101.255.254191.101.255.25565,534
103191.102.0.0/16191.102.0.1 to 191.102.255.254191.102.255.25565,534
104191.103.0.0/16191.103.0.1 to 191.103.255.254191.103.255.25565,534
105191.104.0.0/16191.104.0.1 to 191.104.255.254191.104.255.25565,534
106191.105.0.0/16191.105.0.1 to 191.105.255.254191.105.255.25565,534
107191.106.0.0/16191.106.0.1 to 191.106.255.254191.106.255.25565,534
108191.107.0.0/16191.107.0.1 to 191.107.255.254191.107.255.25565,534
109191.108.0.0/16191.108.0.1 to 191.108.255.254191.108.255.25565,534
110191.109.0.0/16191.109.0.1 to 191.109.255.254191.109.255.25565,534
111191.110.0.0/16191.110.0.1 to 191.110.255.254191.110.255.25565,534
112191.111.0.0/16191.111.0.1 to 191.111.255.254191.111.255.25565,534
113191.112.0.0/16191.112.0.1 to 191.112.255.254191.112.255.25565,534
114191.113.0.0/16191.113.0.1 to 191.113.255.254191.113.255.25565,534
115191.114.0.0/16191.114.0.1 to 191.114.255.254191.114.255.25565,534
116191.115.0.0/16191.115.0.1 to 191.115.255.254191.115.255.25565,534
117191.116.0.0/16191.116.0.1 to 191.116.255.254191.116.255.25565,534
118191.117.0.0/16191.117.0.1 to 191.117.255.254191.117.255.25565,534
119191.118.0.0/16191.118.0.1 to 191.118.255.254191.118.255.25565,534
120191.119.0.0/16191.119.0.1 to 191.119.255.254191.119.255.25565,534
121191.120.0.0/16191.120.0.1 to 191.120.255.254191.120.255.25565,534
122191.121.0.0/16191.121.0.1 to 191.121.255.254191.121.255.25565,534
123191.122.0.0/16191.122.0.1 to 191.122.255.254191.122.255.25565,534
124191.123.0.0/16191.123.0.1 to 191.123.255.254191.123.255.25565,534
125191.124.0.0/16191.124.0.1 to 191.124.255.254191.124.255.25565,534
126191.125.0.0/16191.125.0.1 to 191.125.255.254191.125.255.25565,534
127191.126.0.0/16191.126.0.1 to 191.126.255.254191.126.255.25565,534
128191.127.0.0/16191.127.0.1 to 191.127.255.254191.127.255.25565,534

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.