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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.

Network131.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
131.0.0.0
Broadcast address
131.127.255.255
First usable
131.0.0.1
Last usable
131.127.255.254
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 83000000 · Integer 2197815296 to 2206203903
Reverse DNS zones
0.131.in-addr.arpa
1.131.in-addr.arpa
2.131.in-addr.arpa
3.131.in-addr.arpa
4.131.in-addr.arpa
5.131.in-addr.arpa
6.131.in-addr.arpa
7.131.in-addr.arpa
8.131.in-addr.arpa
9.131.in-addr.arpa
10.131.in-addr.arpa
11.131.in-addr.arpa
12.131.in-addr.arpa
13.131.in-addr.arpa
14.131.in-addr.arpa
15.131.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
Address10000011.00000000.00000000.00000000131.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network10000011.00000000.00000000.00000000131.0.0.0
Broadcast10000011.01111111.11111111.11111111131.127.255.255
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)

131.0.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1131.0.0.0/16131.0.0.1 to 131.0.255.254131.0.255.25565,534
2131.1.0.0/16131.1.0.1 to 131.1.255.254131.1.255.25565,534
3131.2.0.0/16131.2.0.1 to 131.2.255.254131.2.255.25565,534
4131.3.0.0/16131.3.0.1 to 131.3.255.254131.3.255.25565,534
5131.4.0.0/16131.4.0.1 to 131.4.255.254131.4.255.25565,534
6131.5.0.0/16131.5.0.1 to 131.5.255.254131.5.255.25565,534
7131.6.0.0/16131.6.0.1 to 131.6.255.254131.6.255.25565,534
8131.7.0.0/16131.7.0.1 to 131.7.255.254131.7.255.25565,534
9131.8.0.0/16131.8.0.1 to 131.8.255.254131.8.255.25565,534
10131.9.0.0/16131.9.0.1 to 131.9.255.254131.9.255.25565,534
11131.10.0.0/16131.10.0.1 to 131.10.255.254131.10.255.25565,534
12131.11.0.0/16131.11.0.1 to 131.11.255.254131.11.255.25565,534
13131.12.0.0/16131.12.0.1 to 131.12.255.254131.12.255.25565,534
14131.13.0.0/16131.13.0.1 to 131.13.255.254131.13.255.25565,534
15131.14.0.0/16131.14.0.1 to 131.14.255.254131.14.255.25565,534
16131.15.0.0/16131.15.0.1 to 131.15.255.254131.15.255.25565,534
17131.16.0.0/16131.16.0.1 to 131.16.255.254131.16.255.25565,534
18131.17.0.0/16131.17.0.1 to 131.17.255.254131.17.255.25565,534
19131.18.0.0/16131.18.0.1 to 131.18.255.254131.18.255.25565,534
20131.19.0.0/16131.19.0.1 to 131.19.255.254131.19.255.25565,534
21131.20.0.0/16131.20.0.1 to 131.20.255.254131.20.255.25565,534
22131.21.0.0/16131.21.0.1 to 131.21.255.254131.21.255.25565,534
23131.22.0.0/16131.22.0.1 to 131.22.255.254131.22.255.25565,534
24131.23.0.0/16131.23.0.1 to 131.23.255.254131.23.255.25565,534
25131.24.0.0/16131.24.0.1 to 131.24.255.254131.24.255.25565,534
26131.25.0.0/16131.25.0.1 to 131.25.255.254131.25.255.25565,534
27131.26.0.0/16131.26.0.1 to 131.26.255.254131.26.255.25565,534
28131.27.0.0/16131.27.0.1 to 131.27.255.254131.27.255.25565,534
29131.28.0.0/16131.28.0.1 to 131.28.255.254131.28.255.25565,534
30131.29.0.0/16131.29.0.1 to 131.29.255.254131.29.255.25565,534
31131.30.0.0/16131.30.0.1 to 131.30.255.254131.30.255.25565,534
32131.31.0.0/16131.31.0.1 to 131.31.255.254131.31.255.25565,534
33131.32.0.0/16131.32.0.1 to 131.32.255.254131.32.255.25565,534
34131.33.0.0/16131.33.0.1 to 131.33.255.254131.33.255.25565,534
35131.34.0.0/16131.34.0.1 to 131.34.255.254131.34.255.25565,534
36131.35.0.0/16131.35.0.1 to 131.35.255.254131.35.255.25565,534
37131.36.0.0/16131.36.0.1 to 131.36.255.254131.36.255.25565,534
38131.37.0.0/16131.37.0.1 to 131.37.255.254131.37.255.25565,534
39131.38.0.0/16131.38.0.1 to 131.38.255.254131.38.255.25565,534
40131.39.0.0/16131.39.0.1 to 131.39.255.254131.39.255.25565,534
41131.40.0.0/16131.40.0.1 to 131.40.255.254131.40.255.25565,534
42131.41.0.0/16131.41.0.1 to 131.41.255.254131.41.255.25565,534
43131.42.0.0/16131.42.0.1 to 131.42.255.254131.42.255.25565,534
44131.43.0.0/16131.43.0.1 to 131.43.255.254131.43.255.25565,534
45131.44.0.0/16131.44.0.1 to 131.44.255.254131.44.255.25565,534
46131.45.0.0/16131.45.0.1 to 131.45.255.254131.45.255.25565,534
47131.46.0.0/16131.46.0.1 to 131.46.255.254131.46.255.25565,534
48131.47.0.0/16131.47.0.1 to 131.47.255.254131.47.255.25565,534
49131.48.0.0/16131.48.0.1 to 131.48.255.254131.48.255.25565,534
50131.49.0.0/16131.49.0.1 to 131.49.255.254131.49.255.25565,534
51131.50.0.0/16131.50.0.1 to 131.50.255.254131.50.255.25565,534
52131.51.0.0/16131.51.0.1 to 131.51.255.254131.51.255.25565,534
53131.52.0.0/16131.52.0.1 to 131.52.255.254131.52.255.25565,534
54131.53.0.0/16131.53.0.1 to 131.53.255.254131.53.255.25565,534
55131.54.0.0/16131.54.0.1 to 131.54.255.254131.54.255.25565,534
56131.55.0.0/16131.55.0.1 to 131.55.255.254131.55.255.25565,534
57131.56.0.0/16131.56.0.1 to 131.56.255.254131.56.255.25565,534
58131.57.0.0/16131.57.0.1 to 131.57.255.254131.57.255.25565,534
59131.58.0.0/16131.58.0.1 to 131.58.255.254131.58.255.25565,534
60131.59.0.0/16131.59.0.1 to 131.59.255.254131.59.255.25565,534
61131.60.0.0/16131.60.0.1 to 131.60.255.254131.60.255.25565,534
62131.61.0.0/16131.61.0.1 to 131.61.255.254131.61.255.25565,534
63131.62.0.0/16131.62.0.1 to 131.62.255.254131.62.255.25565,534
64131.63.0.0/16131.63.0.1 to 131.63.255.254131.63.255.25565,534
65131.64.0.0/16131.64.0.1 to 131.64.255.254131.64.255.25565,534
66131.65.0.0/16131.65.0.1 to 131.65.255.254131.65.255.25565,534
67131.66.0.0/16131.66.0.1 to 131.66.255.254131.66.255.25565,534
68131.67.0.0/16131.67.0.1 to 131.67.255.254131.67.255.25565,534
69131.68.0.0/16131.68.0.1 to 131.68.255.254131.68.255.25565,534
70131.69.0.0/16131.69.0.1 to 131.69.255.254131.69.255.25565,534
71131.70.0.0/16131.70.0.1 to 131.70.255.254131.70.255.25565,534
72131.71.0.0/16131.71.0.1 to 131.71.255.254131.71.255.25565,534
73131.72.0.0/16131.72.0.1 to 131.72.255.254131.72.255.25565,534
74131.73.0.0/16131.73.0.1 to 131.73.255.254131.73.255.25565,534
75131.74.0.0/16131.74.0.1 to 131.74.255.254131.74.255.25565,534
76131.75.0.0/16131.75.0.1 to 131.75.255.254131.75.255.25565,534
77131.76.0.0/16131.76.0.1 to 131.76.255.254131.76.255.25565,534
78131.77.0.0/16131.77.0.1 to 131.77.255.254131.77.255.25565,534
79131.78.0.0/16131.78.0.1 to 131.78.255.254131.78.255.25565,534
80131.79.0.0/16131.79.0.1 to 131.79.255.254131.79.255.25565,534
81131.80.0.0/16131.80.0.1 to 131.80.255.254131.80.255.25565,534
82131.81.0.0/16131.81.0.1 to 131.81.255.254131.81.255.25565,534
83131.82.0.0/16131.82.0.1 to 131.82.255.254131.82.255.25565,534
84131.83.0.0/16131.83.0.1 to 131.83.255.254131.83.255.25565,534
85131.84.0.0/16131.84.0.1 to 131.84.255.254131.84.255.25565,534
86131.85.0.0/16131.85.0.1 to 131.85.255.254131.85.255.25565,534
87131.86.0.0/16131.86.0.1 to 131.86.255.254131.86.255.25565,534
88131.87.0.0/16131.87.0.1 to 131.87.255.254131.87.255.25565,534
89131.88.0.0/16131.88.0.1 to 131.88.255.254131.88.255.25565,534
90131.89.0.0/16131.89.0.1 to 131.89.255.254131.89.255.25565,534
91131.90.0.0/16131.90.0.1 to 131.90.255.254131.90.255.25565,534
92131.91.0.0/16131.91.0.1 to 131.91.255.254131.91.255.25565,534
93131.92.0.0/16131.92.0.1 to 131.92.255.254131.92.255.25565,534
94131.93.0.0/16131.93.0.1 to 131.93.255.254131.93.255.25565,534
95131.94.0.0/16131.94.0.1 to 131.94.255.254131.94.255.25565,534
96131.95.0.0/16131.95.0.1 to 131.95.255.254131.95.255.25565,534
97131.96.0.0/16131.96.0.1 to 131.96.255.254131.96.255.25565,534
98131.97.0.0/16131.97.0.1 to 131.97.255.254131.97.255.25565,534
99131.98.0.0/16131.98.0.1 to 131.98.255.254131.98.255.25565,534
100131.99.0.0/16131.99.0.1 to 131.99.255.254131.99.255.25565,534
101131.100.0.0/16131.100.0.1 to 131.100.255.254131.100.255.25565,534
102131.101.0.0/16131.101.0.1 to 131.101.255.254131.101.255.25565,534
103131.102.0.0/16131.102.0.1 to 131.102.255.254131.102.255.25565,534
104131.103.0.0/16131.103.0.1 to 131.103.255.254131.103.255.25565,534
105131.104.0.0/16131.104.0.1 to 131.104.255.254131.104.255.25565,534
106131.105.0.0/16131.105.0.1 to 131.105.255.254131.105.255.25565,534
107131.106.0.0/16131.106.0.1 to 131.106.255.254131.106.255.25565,534
108131.107.0.0/16131.107.0.1 to 131.107.255.254131.107.255.25565,534
109131.108.0.0/16131.108.0.1 to 131.108.255.254131.108.255.25565,534
110131.109.0.0/16131.109.0.1 to 131.109.255.254131.109.255.25565,534
111131.110.0.0/16131.110.0.1 to 131.110.255.254131.110.255.25565,534
112131.111.0.0/16131.111.0.1 to 131.111.255.254131.111.255.25565,534
113131.112.0.0/16131.112.0.1 to 131.112.255.254131.112.255.25565,534
114131.113.0.0/16131.113.0.1 to 131.113.255.254131.113.255.25565,534
115131.114.0.0/16131.114.0.1 to 131.114.255.254131.114.255.25565,534
116131.115.0.0/16131.115.0.1 to 131.115.255.254131.115.255.25565,534
117131.116.0.0/16131.116.0.1 to 131.116.255.254131.116.255.25565,534
118131.117.0.0/16131.117.0.1 to 131.117.255.254131.117.255.25565,534
119131.118.0.0/16131.118.0.1 to 131.118.255.254131.118.255.25565,534
120131.119.0.0/16131.119.0.1 to 131.119.255.254131.119.255.25565,534
121131.120.0.0/16131.120.0.1 to 131.120.255.254131.120.255.25565,534
122131.121.0.0/16131.121.0.1 to 131.121.255.254131.121.255.25565,534
123131.122.0.0/16131.122.0.1 to 131.122.255.254131.122.255.25565,534
124131.123.0.0/16131.123.0.1 to 131.123.255.254131.123.255.25565,534
125131.124.0.0/16131.124.0.1 to 131.124.255.254131.124.255.25565,534
126131.125.0.0/16131.125.0.1 to 131.125.255.254131.125.255.25565,534
127131.126.0.0/16131.126.0.1 to 131.126.255.254131.126.255.25565,534
128131.127.0.0/16131.127.0.1 to 131.127.255.254131.127.255.25565,534

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.