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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.

Network247.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
247.0.0.0
Broadcast address
247.255.255.255
First usable
247.0.0.1
Last usable
247.255.255.254
Usable hosts
16,777,214 (16,777,216 less the network and broadcast addresses)
Subnet mask
255.0.0.0
Wildcard mask
0.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/8
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F7000000 · Integer 4143972352 to 4160749567
Reverse DNS zone
247.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11110111..00000000.00000000.00000000247.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network11110111..00000000.00000000.00000000247.0.0.0
Broadcast11110111..11111111.11111111.11111111247.255.255.255
Split into smaller subnets/15
/9 (2)/10 (4)/11 (8)/12 (16)/13 (32)/14 (64)/15 (128)/16 (256)/17 (512)/18 (1,024)/19 (2,048)/20 (4,096)

247.0.0.0/8 makes 128 subnets of /15.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1247.0.0.0/15247.0.0.1 to 247.1.255.254247.1.255.255131,070
2247.2.0.0/15247.2.0.1 to 247.3.255.254247.3.255.255131,070
3247.4.0.0/15247.4.0.1 to 247.5.255.254247.5.255.255131,070
4247.6.0.0/15247.6.0.1 to 247.7.255.254247.7.255.255131,070
5247.8.0.0/15247.8.0.1 to 247.9.255.254247.9.255.255131,070
6247.10.0.0/15247.10.0.1 to 247.11.255.254247.11.255.255131,070
7247.12.0.0/15247.12.0.1 to 247.13.255.254247.13.255.255131,070
8247.14.0.0/15247.14.0.1 to 247.15.255.254247.15.255.255131,070
9247.16.0.0/15247.16.0.1 to 247.17.255.254247.17.255.255131,070
10247.18.0.0/15247.18.0.1 to 247.19.255.254247.19.255.255131,070
11247.20.0.0/15247.20.0.1 to 247.21.255.254247.21.255.255131,070
12247.22.0.0/15247.22.0.1 to 247.23.255.254247.23.255.255131,070
13247.24.0.0/15247.24.0.1 to 247.25.255.254247.25.255.255131,070
14247.26.0.0/15247.26.0.1 to 247.27.255.254247.27.255.255131,070
15247.28.0.0/15247.28.0.1 to 247.29.255.254247.29.255.255131,070
16247.30.0.0/15247.30.0.1 to 247.31.255.254247.31.255.255131,070
17247.32.0.0/15247.32.0.1 to 247.33.255.254247.33.255.255131,070
18247.34.0.0/15247.34.0.1 to 247.35.255.254247.35.255.255131,070
19247.36.0.0/15247.36.0.1 to 247.37.255.254247.37.255.255131,070
20247.38.0.0/15247.38.0.1 to 247.39.255.254247.39.255.255131,070
21247.40.0.0/15247.40.0.1 to 247.41.255.254247.41.255.255131,070
22247.42.0.0/15247.42.0.1 to 247.43.255.254247.43.255.255131,070
23247.44.0.0/15247.44.0.1 to 247.45.255.254247.45.255.255131,070
24247.46.0.0/15247.46.0.1 to 247.47.255.254247.47.255.255131,070
25247.48.0.0/15247.48.0.1 to 247.49.255.254247.49.255.255131,070
26247.50.0.0/15247.50.0.1 to 247.51.255.254247.51.255.255131,070
27247.52.0.0/15247.52.0.1 to 247.53.255.254247.53.255.255131,070
28247.54.0.0/15247.54.0.1 to 247.55.255.254247.55.255.255131,070
29247.56.0.0/15247.56.0.1 to 247.57.255.254247.57.255.255131,070
30247.58.0.0/15247.58.0.1 to 247.59.255.254247.59.255.255131,070
31247.60.0.0/15247.60.0.1 to 247.61.255.254247.61.255.255131,070
32247.62.0.0/15247.62.0.1 to 247.63.255.254247.63.255.255131,070
33247.64.0.0/15247.64.0.1 to 247.65.255.254247.65.255.255131,070
34247.66.0.0/15247.66.0.1 to 247.67.255.254247.67.255.255131,070
35247.68.0.0/15247.68.0.1 to 247.69.255.254247.69.255.255131,070
36247.70.0.0/15247.70.0.1 to 247.71.255.254247.71.255.255131,070
37247.72.0.0/15247.72.0.1 to 247.73.255.254247.73.255.255131,070
38247.74.0.0/15247.74.0.1 to 247.75.255.254247.75.255.255131,070
39247.76.0.0/15247.76.0.1 to 247.77.255.254247.77.255.255131,070
40247.78.0.0/15247.78.0.1 to 247.79.255.254247.79.255.255131,070
41247.80.0.0/15247.80.0.1 to 247.81.255.254247.81.255.255131,070
42247.82.0.0/15247.82.0.1 to 247.83.255.254247.83.255.255131,070
43247.84.0.0/15247.84.0.1 to 247.85.255.254247.85.255.255131,070
44247.86.0.0/15247.86.0.1 to 247.87.255.254247.87.255.255131,070
45247.88.0.0/15247.88.0.1 to 247.89.255.254247.89.255.255131,070
46247.90.0.0/15247.90.0.1 to 247.91.255.254247.91.255.255131,070
47247.92.0.0/15247.92.0.1 to 247.93.255.254247.93.255.255131,070
48247.94.0.0/15247.94.0.1 to 247.95.255.254247.95.255.255131,070
49247.96.0.0/15247.96.0.1 to 247.97.255.254247.97.255.255131,070
50247.98.0.0/15247.98.0.1 to 247.99.255.254247.99.255.255131,070
51247.100.0.0/15247.100.0.1 to 247.101.255.254247.101.255.255131,070
52247.102.0.0/15247.102.0.1 to 247.103.255.254247.103.255.255131,070
53247.104.0.0/15247.104.0.1 to 247.105.255.254247.105.255.255131,070
54247.106.0.0/15247.106.0.1 to 247.107.255.254247.107.255.255131,070
55247.108.0.0/15247.108.0.1 to 247.109.255.254247.109.255.255131,070
56247.110.0.0/15247.110.0.1 to 247.111.255.254247.111.255.255131,070
57247.112.0.0/15247.112.0.1 to 247.113.255.254247.113.255.255131,070
58247.114.0.0/15247.114.0.1 to 247.115.255.254247.115.255.255131,070
59247.116.0.0/15247.116.0.1 to 247.117.255.254247.117.255.255131,070
60247.118.0.0/15247.118.0.1 to 247.119.255.254247.119.255.255131,070
61247.120.0.0/15247.120.0.1 to 247.121.255.254247.121.255.255131,070
62247.122.0.0/15247.122.0.1 to 247.123.255.254247.123.255.255131,070
63247.124.0.0/15247.124.0.1 to 247.125.255.254247.125.255.255131,070
64247.126.0.0/15247.126.0.1 to 247.127.255.254247.127.255.255131,070
65247.128.0.0/15247.128.0.1 to 247.129.255.254247.129.255.255131,070
66247.130.0.0/15247.130.0.1 to 247.131.255.254247.131.255.255131,070
67247.132.0.0/15247.132.0.1 to 247.133.255.254247.133.255.255131,070
68247.134.0.0/15247.134.0.1 to 247.135.255.254247.135.255.255131,070
69247.136.0.0/15247.136.0.1 to 247.137.255.254247.137.255.255131,070
70247.138.0.0/15247.138.0.1 to 247.139.255.254247.139.255.255131,070
71247.140.0.0/15247.140.0.1 to 247.141.255.254247.141.255.255131,070
72247.142.0.0/15247.142.0.1 to 247.143.255.254247.143.255.255131,070
73247.144.0.0/15247.144.0.1 to 247.145.255.254247.145.255.255131,070
74247.146.0.0/15247.146.0.1 to 247.147.255.254247.147.255.255131,070
75247.148.0.0/15247.148.0.1 to 247.149.255.254247.149.255.255131,070
76247.150.0.0/15247.150.0.1 to 247.151.255.254247.151.255.255131,070
77247.152.0.0/15247.152.0.1 to 247.153.255.254247.153.255.255131,070
78247.154.0.0/15247.154.0.1 to 247.155.255.254247.155.255.255131,070
79247.156.0.0/15247.156.0.1 to 247.157.255.254247.157.255.255131,070
80247.158.0.0/15247.158.0.1 to 247.159.255.254247.159.255.255131,070
81247.160.0.0/15247.160.0.1 to 247.161.255.254247.161.255.255131,070
82247.162.0.0/15247.162.0.1 to 247.163.255.254247.163.255.255131,070
83247.164.0.0/15247.164.0.1 to 247.165.255.254247.165.255.255131,070
84247.166.0.0/15247.166.0.1 to 247.167.255.254247.167.255.255131,070
85247.168.0.0/15247.168.0.1 to 247.169.255.254247.169.255.255131,070
86247.170.0.0/15247.170.0.1 to 247.171.255.254247.171.255.255131,070
87247.172.0.0/15247.172.0.1 to 247.173.255.254247.173.255.255131,070
88247.174.0.0/15247.174.0.1 to 247.175.255.254247.175.255.255131,070
89247.176.0.0/15247.176.0.1 to 247.177.255.254247.177.255.255131,070
90247.178.0.0/15247.178.0.1 to 247.179.255.254247.179.255.255131,070
91247.180.0.0/15247.180.0.1 to 247.181.255.254247.181.255.255131,070
92247.182.0.0/15247.182.0.1 to 247.183.255.254247.183.255.255131,070
93247.184.0.0/15247.184.0.1 to 247.185.255.254247.185.255.255131,070
94247.186.0.0/15247.186.0.1 to 247.187.255.254247.187.255.255131,070
95247.188.0.0/15247.188.0.1 to 247.189.255.254247.189.255.255131,070
96247.190.0.0/15247.190.0.1 to 247.191.255.254247.191.255.255131,070
97247.192.0.0/15247.192.0.1 to 247.193.255.254247.193.255.255131,070
98247.194.0.0/15247.194.0.1 to 247.195.255.254247.195.255.255131,070
99247.196.0.0/15247.196.0.1 to 247.197.255.254247.197.255.255131,070
100247.198.0.0/15247.198.0.1 to 247.199.255.254247.199.255.255131,070
101247.200.0.0/15247.200.0.1 to 247.201.255.254247.201.255.255131,070
102247.202.0.0/15247.202.0.1 to 247.203.255.254247.203.255.255131,070
103247.204.0.0/15247.204.0.1 to 247.205.255.254247.205.255.255131,070
104247.206.0.0/15247.206.0.1 to 247.207.255.254247.207.255.255131,070
105247.208.0.0/15247.208.0.1 to 247.209.255.254247.209.255.255131,070
106247.210.0.0/15247.210.0.1 to 247.211.255.254247.211.255.255131,070
107247.212.0.0/15247.212.0.1 to 247.213.255.254247.213.255.255131,070
108247.214.0.0/15247.214.0.1 to 247.215.255.254247.215.255.255131,070
109247.216.0.0/15247.216.0.1 to 247.217.255.254247.217.255.255131,070
110247.218.0.0/15247.218.0.1 to 247.219.255.254247.219.255.255131,070
111247.220.0.0/15247.220.0.1 to 247.221.255.254247.221.255.255131,070
112247.222.0.0/15247.222.0.1 to 247.223.255.254247.223.255.255131,070
113247.224.0.0/15247.224.0.1 to 247.225.255.254247.225.255.255131,070
114247.226.0.0/15247.226.0.1 to 247.227.255.254247.227.255.255131,070
115247.228.0.0/15247.228.0.1 to 247.229.255.254247.229.255.255131,070
116247.230.0.0/15247.230.0.1 to 247.231.255.254247.231.255.255131,070
117247.232.0.0/15247.232.0.1 to 247.233.255.254247.233.255.255131,070
118247.234.0.0/15247.234.0.1 to 247.235.255.254247.235.255.255131,070
119247.236.0.0/15247.236.0.1 to 247.237.255.254247.237.255.255131,070
120247.238.0.0/15247.238.0.1 to 247.239.255.254247.239.255.255131,070
121247.240.0.0/15247.240.0.1 to 247.241.255.254247.241.255.255131,070
122247.242.0.0/15247.242.0.1 to 247.243.255.254247.243.255.255131,070
123247.244.0.0/15247.244.0.1 to 247.245.255.254247.245.255.255131,070
124247.246.0.0/15247.246.0.1 to 247.247.255.254247.247.255.255131,070
125247.248.0.0/15247.248.0.1 to 247.249.255.254247.249.255.255131,070
126247.250.0.0/15247.250.0.1 to 247.251.255.254247.251.255.255131,070
127247.252.0.0/15247.252.0.1 to 247.253.255.254247.253.255.255131,070
128247.254.0.0/15247.254.0.1 to 247.255.255.254247.255.255.255131,070

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.