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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.

Network216.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
216.0.0.0
Broadcast address
216.127.255.255
First usable
216.0.0.1
Last usable
216.127.255.254
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
C (default /24)
As numbers
Hex D8000000 · Integer 3623878656 to 3632267263
Reverse DNS zones
0.216.in-addr.arpa
1.216.in-addr.arpa
2.216.in-addr.arpa
3.216.in-addr.arpa
4.216.in-addr.arpa
5.216.in-addr.arpa
6.216.in-addr.arpa
7.216.in-addr.arpa
8.216.in-addr.arpa
9.216.in-addr.arpa
10.216.in-addr.arpa
11.216.in-addr.arpa
12.216.in-addr.arpa
13.216.in-addr.arpa
14.216.in-addr.arpa
15.216.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
Address11011000.00000000.00000000.00000000216.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network11011000.00000000.00000000.00000000216.0.0.0
Broadcast11011000.01111111.11111111.11111111216.127.255.255
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)

216.0.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1216.0.0.0/16216.0.0.1 to 216.0.255.254216.0.255.25565,534
2216.1.0.0/16216.1.0.1 to 216.1.255.254216.1.255.25565,534
3216.2.0.0/16216.2.0.1 to 216.2.255.254216.2.255.25565,534
4216.3.0.0/16216.3.0.1 to 216.3.255.254216.3.255.25565,534
5216.4.0.0/16216.4.0.1 to 216.4.255.254216.4.255.25565,534
6216.5.0.0/16216.5.0.1 to 216.5.255.254216.5.255.25565,534
7216.6.0.0/16216.6.0.1 to 216.6.255.254216.6.255.25565,534
8216.7.0.0/16216.7.0.1 to 216.7.255.254216.7.255.25565,534
9216.8.0.0/16216.8.0.1 to 216.8.255.254216.8.255.25565,534
10216.9.0.0/16216.9.0.1 to 216.9.255.254216.9.255.25565,534
11216.10.0.0/16216.10.0.1 to 216.10.255.254216.10.255.25565,534
12216.11.0.0/16216.11.0.1 to 216.11.255.254216.11.255.25565,534
13216.12.0.0/16216.12.0.1 to 216.12.255.254216.12.255.25565,534
14216.13.0.0/16216.13.0.1 to 216.13.255.254216.13.255.25565,534
15216.14.0.0/16216.14.0.1 to 216.14.255.254216.14.255.25565,534
16216.15.0.0/16216.15.0.1 to 216.15.255.254216.15.255.25565,534
17216.16.0.0/16216.16.0.1 to 216.16.255.254216.16.255.25565,534
18216.17.0.0/16216.17.0.1 to 216.17.255.254216.17.255.25565,534
19216.18.0.0/16216.18.0.1 to 216.18.255.254216.18.255.25565,534
20216.19.0.0/16216.19.0.1 to 216.19.255.254216.19.255.25565,534
21216.20.0.0/16216.20.0.1 to 216.20.255.254216.20.255.25565,534
22216.21.0.0/16216.21.0.1 to 216.21.255.254216.21.255.25565,534
23216.22.0.0/16216.22.0.1 to 216.22.255.254216.22.255.25565,534
24216.23.0.0/16216.23.0.1 to 216.23.255.254216.23.255.25565,534
25216.24.0.0/16216.24.0.1 to 216.24.255.254216.24.255.25565,534
26216.25.0.0/16216.25.0.1 to 216.25.255.254216.25.255.25565,534
27216.26.0.0/16216.26.0.1 to 216.26.255.254216.26.255.25565,534
28216.27.0.0/16216.27.0.1 to 216.27.255.254216.27.255.25565,534
29216.28.0.0/16216.28.0.1 to 216.28.255.254216.28.255.25565,534
30216.29.0.0/16216.29.0.1 to 216.29.255.254216.29.255.25565,534
31216.30.0.0/16216.30.0.1 to 216.30.255.254216.30.255.25565,534
32216.31.0.0/16216.31.0.1 to 216.31.255.254216.31.255.25565,534
33216.32.0.0/16216.32.0.1 to 216.32.255.254216.32.255.25565,534
34216.33.0.0/16216.33.0.1 to 216.33.255.254216.33.255.25565,534
35216.34.0.0/16216.34.0.1 to 216.34.255.254216.34.255.25565,534
36216.35.0.0/16216.35.0.1 to 216.35.255.254216.35.255.25565,534
37216.36.0.0/16216.36.0.1 to 216.36.255.254216.36.255.25565,534
38216.37.0.0/16216.37.0.1 to 216.37.255.254216.37.255.25565,534
39216.38.0.0/16216.38.0.1 to 216.38.255.254216.38.255.25565,534
40216.39.0.0/16216.39.0.1 to 216.39.255.254216.39.255.25565,534
41216.40.0.0/16216.40.0.1 to 216.40.255.254216.40.255.25565,534
42216.41.0.0/16216.41.0.1 to 216.41.255.254216.41.255.25565,534
43216.42.0.0/16216.42.0.1 to 216.42.255.254216.42.255.25565,534
44216.43.0.0/16216.43.0.1 to 216.43.255.254216.43.255.25565,534
45216.44.0.0/16216.44.0.1 to 216.44.255.254216.44.255.25565,534
46216.45.0.0/16216.45.0.1 to 216.45.255.254216.45.255.25565,534
47216.46.0.0/16216.46.0.1 to 216.46.255.254216.46.255.25565,534
48216.47.0.0/16216.47.0.1 to 216.47.255.254216.47.255.25565,534
49216.48.0.0/16216.48.0.1 to 216.48.255.254216.48.255.25565,534
50216.49.0.0/16216.49.0.1 to 216.49.255.254216.49.255.25565,534
51216.50.0.0/16216.50.0.1 to 216.50.255.254216.50.255.25565,534
52216.51.0.0/16216.51.0.1 to 216.51.255.254216.51.255.25565,534
53216.52.0.0/16216.52.0.1 to 216.52.255.254216.52.255.25565,534
54216.53.0.0/16216.53.0.1 to 216.53.255.254216.53.255.25565,534
55216.54.0.0/16216.54.0.1 to 216.54.255.254216.54.255.25565,534
56216.55.0.0/16216.55.0.1 to 216.55.255.254216.55.255.25565,534
57216.56.0.0/16216.56.0.1 to 216.56.255.254216.56.255.25565,534
58216.57.0.0/16216.57.0.1 to 216.57.255.254216.57.255.25565,534
59216.58.0.0/16216.58.0.1 to 216.58.255.254216.58.255.25565,534
60216.59.0.0/16216.59.0.1 to 216.59.255.254216.59.255.25565,534
61216.60.0.0/16216.60.0.1 to 216.60.255.254216.60.255.25565,534
62216.61.0.0/16216.61.0.1 to 216.61.255.254216.61.255.25565,534
63216.62.0.0/16216.62.0.1 to 216.62.255.254216.62.255.25565,534
64216.63.0.0/16216.63.0.1 to 216.63.255.254216.63.255.25565,534
65216.64.0.0/16216.64.0.1 to 216.64.255.254216.64.255.25565,534
66216.65.0.0/16216.65.0.1 to 216.65.255.254216.65.255.25565,534
67216.66.0.0/16216.66.0.1 to 216.66.255.254216.66.255.25565,534
68216.67.0.0/16216.67.0.1 to 216.67.255.254216.67.255.25565,534
69216.68.0.0/16216.68.0.1 to 216.68.255.254216.68.255.25565,534
70216.69.0.0/16216.69.0.1 to 216.69.255.254216.69.255.25565,534
71216.70.0.0/16216.70.0.1 to 216.70.255.254216.70.255.25565,534
72216.71.0.0/16216.71.0.1 to 216.71.255.254216.71.255.25565,534
73216.72.0.0/16216.72.0.1 to 216.72.255.254216.72.255.25565,534
74216.73.0.0/16216.73.0.1 to 216.73.255.254216.73.255.25565,534
75216.74.0.0/16216.74.0.1 to 216.74.255.254216.74.255.25565,534
76216.75.0.0/16216.75.0.1 to 216.75.255.254216.75.255.25565,534
77216.76.0.0/16216.76.0.1 to 216.76.255.254216.76.255.25565,534
78216.77.0.0/16216.77.0.1 to 216.77.255.254216.77.255.25565,534
79216.78.0.0/16216.78.0.1 to 216.78.255.254216.78.255.25565,534
80216.79.0.0/16216.79.0.1 to 216.79.255.254216.79.255.25565,534
81216.80.0.0/16216.80.0.1 to 216.80.255.254216.80.255.25565,534
82216.81.0.0/16216.81.0.1 to 216.81.255.254216.81.255.25565,534
83216.82.0.0/16216.82.0.1 to 216.82.255.254216.82.255.25565,534
84216.83.0.0/16216.83.0.1 to 216.83.255.254216.83.255.25565,534
85216.84.0.0/16216.84.0.1 to 216.84.255.254216.84.255.25565,534
86216.85.0.0/16216.85.0.1 to 216.85.255.254216.85.255.25565,534
87216.86.0.0/16216.86.0.1 to 216.86.255.254216.86.255.25565,534
88216.87.0.0/16216.87.0.1 to 216.87.255.254216.87.255.25565,534
89216.88.0.0/16216.88.0.1 to 216.88.255.254216.88.255.25565,534
90216.89.0.0/16216.89.0.1 to 216.89.255.254216.89.255.25565,534
91216.90.0.0/16216.90.0.1 to 216.90.255.254216.90.255.25565,534
92216.91.0.0/16216.91.0.1 to 216.91.255.254216.91.255.25565,534
93216.92.0.0/16216.92.0.1 to 216.92.255.254216.92.255.25565,534
94216.93.0.0/16216.93.0.1 to 216.93.255.254216.93.255.25565,534
95216.94.0.0/16216.94.0.1 to 216.94.255.254216.94.255.25565,534
96216.95.0.0/16216.95.0.1 to 216.95.255.254216.95.255.25565,534
97216.96.0.0/16216.96.0.1 to 216.96.255.254216.96.255.25565,534
98216.97.0.0/16216.97.0.1 to 216.97.255.254216.97.255.25565,534
99216.98.0.0/16216.98.0.1 to 216.98.255.254216.98.255.25565,534
100216.99.0.0/16216.99.0.1 to 216.99.255.254216.99.255.25565,534
101216.100.0.0/16216.100.0.1 to 216.100.255.254216.100.255.25565,534
102216.101.0.0/16216.101.0.1 to 216.101.255.254216.101.255.25565,534
103216.102.0.0/16216.102.0.1 to 216.102.255.254216.102.255.25565,534
104216.103.0.0/16216.103.0.1 to 216.103.255.254216.103.255.25565,534
105216.104.0.0/16216.104.0.1 to 216.104.255.254216.104.255.25565,534
106216.105.0.0/16216.105.0.1 to 216.105.255.254216.105.255.25565,534
107216.106.0.0/16216.106.0.1 to 216.106.255.254216.106.255.25565,534
108216.107.0.0/16216.107.0.1 to 216.107.255.254216.107.255.25565,534
109216.108.0.0/16216.108.0.1 to 216.108.255.254216.108.255.25565,534
110216.109.0.0/16216.109.0.1 to 216.109.255.254216.109.255.25565,534
111216.110.0.0/16216.110.0.1 to 216.110.255.254216.110.255.25565,534
112216.111.0.0/16216.111.0.1 to 216.111.255.254216.111.255.25565,534
113216.112.0.0/16216.112.0.1 to 216.112.255.254216.112.255.25565,534
114216.113.0.0/16216.113.0.1 to 216.113.255.254216.113.255.25565,534
115216.114.0.0/16216.114.0.1 to 216.114.255.254216.114.255.25565,534
116216.115.0.0/16216.115.0.1 to 216.115.255.254216.115.255.25565,534
117216.116.0.0/16216.116.0.1 to 216.116.255.254216.116.255.25565,534
118216.117.0.0/16216.117.0.1 to 216.117.255.254216.117.255.25565,534
119216.118.0.0/16216.118.0.1 to 216.118.255.254216.118.255.25565,534
120216.119.0.0/16216.119.0.1 to 216.119.255.254216.119.255.25565,534
121216.120.0.0/16216.120.0.1 to 216.120.255.254216.120.255.25565,534
122216.121.0.0/16216.121.0.1 to 216.121.255.254216.121.255.25565,534
123216.122.0.0/16216.122.0.1 to 216.122.255.254216.122.255.25565,534
124216.123.0.0/16216.123.0.1 to 216.123.255.254216.123.255.25565,534
125216.124.0.0/16216.124.0.1 to 216.124.255.254216.124.255.25565,534
126216.125.0.0/16216.125.0.1 to 216.125.255.254216.125.255.25565,534
127216.126.0.0/16216.126.0.1 to 216.126.255.254216.126.255.25565,534
128216.127.0.0/16216.127.0.1 to 216.127.255.254216.127.255.25565,534

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.