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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.

Network231.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
231.0.0.0
Broadcast address
231.127.255.255
First usable
231.0.0.1
Last usable
231.127.255.254
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
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex E7000000 · Integer 3875536896 to 3883925503
Reverse DNS zones
0.231.in-addr.arpa
1.231.in-addr.arpa
2.231.in-addr.arpa
3.231.in-addr.arpa
4.231.in-addr.arpa
5.231.in-addr.arpa
6.231.in-addr.arpa
7.231.in-addr.arpa
8.231.in-addr.arpa
9.231.in-addr.arpa
10.231.in-addr.arpa
11.231.in-addr.arpa
12.231.in-addr.arpa
13.231.in-addr.arpa
14.231.in-addr.arpa
15.231.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
Address11100111.00000000.00000000.00000000231.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network11100111.00000000.00000000.00000000231.0.0.0
Broadcast11100111.01111111.11111111.11111111231.127.255.255
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)

231.0.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1231.0.0.0/16231.0.0.1 to 231.0.255.254231.0.255.25565,534
2231.1.0.0/16231.1.0.1 to 231.1.255.254231.1.255.25565,534
3231.2.0.0/16231.2.0.1 to 231.2.255.254231.2.255.25565,534
4231.3.0.0/16231.3.0.1 to 231.3.255.254231.3.255.25565,534
5231.4.0.0/16231.4.0.1 to 231.4.255.254231.4.255.25565,534
6231.5.0.0/16231.5.0.1 to 231.5.255.254231.5.255.25565,534
7231.6.0.0/16231.6.0.1 to 231.6.255.254231.6.255.25565,534
8231.7.0.0/16231.7.0.1 to 231.7.255.254231.7.255.25565,534
9231.8.0.0/16231.8.0.1 to 231.8.255.254231.8.255.25565,534
10231.9.0.0/16231.9.0.1 to 231.9.255.254231.9.255.25565,534
11231.10.0.0/16231.10.0.1 to 231.10.255.254231.10.255.25565,534
12231.11.0.0/16231.11.0.1 to 231.11.255.254231.11.255.25565,534
13231.12.0.0/16231.12.0.1 to 231.12.255.254231.12.255.25565,534
14231.13.0.0/16231.13.0.1 to 231.13.255.254231.13.255.25565,534
15231.14.0.0/16231.14.0.1 to 231.14.255.254231.14.255.25565,534
16231.15.0.0/16231.15.0.1 to 231.15.255.254231.15.255.25565,534
17231.16.0.0/16231.16.0.1 to 231.16.255.254231.16.255.25565,534
18231.17.0.0/16231.17.0.1 to 231.17.255.254231.17.255.25565,534
19231.18.0.0/16231.18.0.1 to 231.18.255.254231.18.255.25565,534
20231.19.0.0/16231.19.0.1 to 231.19.255.254231.19.255.25565,534
21231.20.0.0/16231.20.0.1 to 231.20.255.254231.20.255.25565,534
22231.21.0.0/16231.21.0.1 to 231.21.255.254231.21.255.25565,534
23231.22.0.0/16231.22.0.1 to 231.22.255.254231.22.255.25565,534
24231.23.0.0/16231.23.0.1 to 231.23.255.254231.23.255.25565,534
25231.24.0.0/16231.24.0.1 to 231.24.255.254231.24.255.25565,534
26231.25.0.0/16231.25.0.1 to 231.25.255.254231.25.255.25565,534
27231.26.0.0/16231.26.0.1 to 231.26.255.254231.26.255.25565,534
28231.27.0.0/16231.27.0.1 to 231.27.255.254231.27.255.25565,534
29231.28.0.0/16231.28.0.1 to 231.28.255.254231.28.255.25565,534
30231.29.0.0/16231.29.0.1 to 231.29.255.254231.29.255.25565,534
31231.30.0.0/16231.30.0.1 to 231.30.255.254231.30.255.25565,534
32231.31.0.0/16231.31.0.1 to 231.31.255.254231.31.255.25565,534
33231.32.0.0/16231.32.0.1 to 231.32.255.254231.32.255.25565,534
34231.33.0.0/16231.33.0.1 to 231.33.255.254231.33.255.25565,534
35231.34.0.0/16231.34.0.1 to 231.34.255.254231.34.255.25565,534
36231.35.0.0/16231.35.0.1 to 231.35.255.254231.35.255.25565,534
37231.36.0.0/16231.36.0.1 to 231.36.255.254231.36.255.25565,534
38231.37.0.0/16231.37.0.1 to 231.37.255.254231.37.255.25565,534
39231.38.0.0/16231.38.0.1 to 231.38.255.254231.38.255.25565,534
40231.39.0.0/16231.39.0.1 to 231.39.255.254231.39.255.25565,534
41231.40.0.0/16231.40.0.1 to 231.40.255.254231.40.255.25565,534
42231.41.0.0/16231.41.0.1 to 231.41.255.254231.41.255.25565,534
43231.42.0.0/16231.42.0.1 to 231.42.255.254231.42.255.25565,534
44231.43.0.0/16231.43.0.1 to 231.43.255.254231.43.255.25565,534
45231.44.0.0/16231.44.0.1 to 231.44.255.254231.44.255.25565,534
46231.45.0.0/16231.45.0.1 to 231.45.255.254231.45.255.25565,534
47231.46.0.0/16231.46.0.1 to 231.46.255.254231.46.255.25565,534
48231.47.0.0/16231.47.0.1 to 231.47.255.254231.47.255.25565,534
49231.48.0.0/16231.48.0.1 to 231.48.255.254231.48.255.25565,534
50231.49.0.0/16231.49.0.1 to 231.49.255.254231.49.255.25565,534
51231.50.0.0/16231.50.0.1 to 231.50.255.254231.50.255.25565,534
52231.51.0.0/16231.51.0.1 to 231.51.255.254231.51.255.25565,534
53231.52.0.0/16231.52.0.1 to 231.52.255.254231.52.255.25565,534
54231.53.0.0/16231.53.0.1 to 231.53.255.254231.53.255.25565,534
55231.54.0.0/16231.54.0.1 to 231.54.255.254231.54.255.25565,534
56231.55.0.0/16231.55.0.1 to 231.55.255.254231.55.255.25565,534
57231.56.0.0/16231.56.0.1 to 231.56.255.254231.56.255.25565,534
58231.57.0.0/16231.57.0.1 to 231.57.255.254231.57.255.25565,534
59231.58.0.0/16231.58.0.1 to 231.58.255.254231.58.255.25565,534
60231.59.0.0/16231.59.0.1 to 231.59.255.254231.59.255.25565,534
61231.60.0.0/16231.60.0.1 to 231.60.255.254231.60.255.25565,534
62231.61.0.0/16231.61.0.1 to 231.61.255.254231.61.255.25565,534
63231.62.0.0/16231.62.0.1 to 231.62.255.254231.62.255.25565,534
64231.63.0.0/16231.63.0.1 to 231.63.255.254231.63.255.25565,534
65231.64.0.0/16231.64.0.1 to 231.64.255.254231.64.255.25565,534
66231.65.0.0/16231.65.0.1 to 231.65.255.254231.65.255.25565,534
67231.66.0.0/16231.66.0.1 to 231.66.255.254231.66.255.25565,534
68231.67.0.0/16231.67.0.1 to 231.67.255.254231.67.255.25565,534
69231.68.0.0/16231.68.0.1 to 231.68.255.254231.68.255.25565,534
70231.69.0.0/16231.69.0.1 to 231.69.255.254231.69.255.25565,534
71231.70.0.0/16231.70.0.1 to 231.70.255.254231.70.255.25565,534
72231.71.0.0/16231.71.0.1 to 231.71.255.254231.71.255.25565,534
73231.72.0.0/16231.72.0.1 to 231.72.255.254231.72.255.25565,534
74231.73.0.0/16231.73.0.1 to 231.73.255.254231.73.255.25565,534
75231.74.0.0/16231.74.0.1 to 231.74.255.254231.74.255.25565,534
76231.75.0.0/16231.75.0.1 to 231.75.255.254231.75.255.25565,534
77231.76.0.0/16231.76.0.1 to 231.76.255.254231.76.255.25565,534
78231.77.0.0/16231.77.0.1 to 231.77.255.254231.77.255.25565,534
79231.78.0.0/16231.78.0.1 to 231.78.255.254231.78.255.25565,534
80231.79.0.0/16231.79.0.1 to 231.79.255.254231.79.255.25565,534
81231.80.0.0/16231.80.0.1 to 231.80.255.254231.80.255.25565,534
82231.81.0.0/16231.81.0.1 to 231.81.255.254231.81.255.25565,534
83231.82.0.0/16231.82.0.1 to 231.82.255.254231.82.255.25565,534
84231.83.0.0/16231.83.0.1 to 231.83.255.254231.83.255.25565,534
85231.84.0.0/16231.84.0.1 to 231.84.255.254231.84.255.25565,534
86231.85.0.0/16231.85.0.1 to 231.85.255.254231.85.255.25565,534
87231.86.0.0/16231.86.0.1 to 231.86.255.254231.86.255.25565,534
88231.87.0.0/16231.87.0.1 to 231.87.255.254231.87.255.25565,534
89231.88.0.0/16231.88.0.1 to 231.88.255.254231.88.255.25565,534
90231.89.0.0/16231.89.0.1 to 231.89.255.254231.89.255.25565,534
91231.90.0.0/16231.90.0.1 to 231.90.255.254231.90.255.25565,534
92231.91.0.0/16231.91.0.1 to 231.91.255.254231.91.255.25565,534
93231.92.0.0/16231.92.0.1 to 231.92.255.254231.92.255.25565,534
94231.93.0.0/16231.93.0.1 to 231.93.255.254231.93.255.25565,534
95231.94.0.0/16231.94.0.1 to 231.94.255.254231.94.255.25565,534
96231.95.0.0/16231.95.0.1 to 231.95.255.254231.95.255.25565,534
97231.96.0.0/16231.96.0.1 to 231.96.255.254231.96.255.25565,534
98231.97.0.0/16231.97.0.1 to 231.97.255.254231.97.255.25565,534
99231.98.0.0/16231.98.0.1 to 231.98.255.254231.98.255.25565,534
100231.99.0.0/16231.99.0.1 to 231.99.255.254231.99.255.25565,534
101231.100.0.0/16231.100.0.1 to 231.100.255.254231.100.255.25565,534
102231.101.0.0/16231.101.0.1 to 231.101.255.254231.101.255.25565,534
103231.102.0.0/16231.102.0.1 to 231.102.255.254231.102.255.25565,534
104231.103.0.0/16231.103.0.1 to 231.103.255.254231.103.255.25565,534
105231.104.0.0/16231.104.0.1 to 231.104.255.254231.104.255.25565,534
106231.105.0.0/16231.105.0.1 to 231.105.255.254231.105.255.25565,534
107231.106.0.0/16231.106.0.1 to 231.106.255.254231.106.255.25565,534
108231.107.0.0/16231.107.0.1 to 231.107.255.254231.107.255.25565,534
109231.108.0.0/16231.108.0.1 to 231.108.255.254231.108.255.25565,534
110231.109.0.0/16231.109.0.1 to 231.109.255.254231.109.255.25565,534
111231.110.0.0/16231.110.0.1 to 231.110.255.254231.110.255.25565,534
112231.111.0.0/16231.111.0.1 to 231.111.255.254231.111.255.25565,534
113231.112.0.0/16231.112.0.1 to 231.112.255.254231.112.255.25565,534
114231.113.0.0/16231.113.0.1 to 231.113.255.254231.113.255.25565,534
115231.114.0.0/16231.114.0.1 to 231.114.255.254231.114.255.25565,534
116231.115.0.0/16231.115.0.1 to 231.115.255.254231.115.255.25565,534
117231.116.0.0/16231.116.0.1 to 231.116.255.254231.116.255.25565,534
118231.117.0.0/16231.117.0.1 to 231.117.255.254231.117.255.25565,534
119231.118.0.0/16231.118.0.1 to 231.118.255.254231.118.255.25565,534
120231.119.0.0/16231.119.0.1 to 231.119.255.254231.119.255.25565,534
121231.120.0.0/16231.120.0.1 to 231.120.255.254231.120.255.25565,534
122231.121.0.0/16231.121.0.1 to 231.121.255.254231.121.255.25565,534
123231.122.0.0/16231.122.0.1 to 231.122.255.254231.122.255.25565,534
124231.123.0.0/16231.123.0.1 to 231.123.255.254231.123.255.25565,534
125231.124.0.0/16231.124.0.1 to 231.124.255.254231.124.255.25565,534
126231.125.0.0/16231.125.0.1 to 231.125.255.254231.125.255.25565,534
127231.126.0.0/16231.126.0.1 to 231.126.255.254231.126.255.25565,534
128231.127.0.0/16231.127.0.1 to 231.127.255.254231.127.255.25565,534

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.