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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.

Network151.0.0.0/8
Usable hosts16,777,214
Subnet mask255.0.0.0
Addresses16,777,216
Network address
151.0.0.0
Broadcast address
151.255.255.255
First usable
151.0.0.1
Last usable
151.255.255.254
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
Public public
Old class
B (default /16)
As numbers
Hex 97000000 · Integer 2533359616 to 2550136831
Reverse DNS zone
151.in-addr.arpa
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10010111..00000000.00000000.00000000151.0.0.0
Subnet mask11111111..00000000.00000000.00000000255.0.0.0
Network10010111..00000000.00000000.00000000151.0.0.0
Broadcast10010111..11111111.11111111.11111111151.255.255.255
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)

151.0.0.0/8 makes 128 subnets of /15.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1151.0.0.0/15151.0.0.1 to 151.1.255.254151.1.255.255131,070
2151.2.0.0/15151.2.0.1 to 151.3.255.254151.3.255.255131,070
3151.4.0.0/15151.4.0.1 to 151.5.255.254151.5.255.255131,070
4151.6.0.0/15151.6.0.1 to 151.7.255.254151.7.255.255131,070
5151.8.0.0/15151.8.0.1 to 151.9.255.254151.9.255.255131,070
6151.10.0.0/15151.10.0.1 to 151.11.255.254151.11.255.255131,070
7151.12.0.0/15151.12.0.1 to 151.13.255.254151.13.255.255131,070
8151.14.0.0/15151.14.0.1 to 151.15.255.254151.15.255.255131,070
9151.16.0.0/15151.16.0.1 to 151.17.255.254151.17.255.255131,070
10151.18.0.0/15151.18.0.1 to 151.19.255.254151.19.255.255131,070
11151.20.0.0/15151.20.0.1 to 151.21.255.254151.21.255.255131,070
12151.22.0.0/15151.22.0.1 to 151.23.255.254151.23.255.255131,070
13151.24.0.0/15151.24.0.1 to 151.25.255.254151.25.255.255131,070
14151.26.0.0/15151.26.0.1 to 151.27.255.254151.27.255.255131,070
15151.28.0.0/15151.28.0.1 to 151.29.255.254151.29.255.255131,070
16151.30.0.0/15151.30.0.1 to 151.31.255.254151.31.255.255131,070
17151.32.0.0/15151.32.0.1 to 151.33.255.254151.33.255.255131,070
18151.34.0.0/15151.34.0.1 to 151.35.255.254151.35.255.255131,070
19151.36.0.0/15151.36.0.1 to 151.37.255.254151.37.255.255131,070
20151.38.0.0/15151.38.0.1 to 151.39.255.254151.39.255.255131,070
21151.40.0.0/15151.40.0.1 to 151.41.255.254151.41.255.255131,070
22151.42.0.0/15151.42.0.1 to 151.43.255.254151.43.255.255131,070
23151.44.0.0/15151.44.0.1 to 151.45.255.254151.45.255.255131,070
24151.46.0.0/15151.46.0.1 to 151.47.255.254151.47.255.255131,070
25151.48.0.0/15151.48.0.1 to 151.49.255.254151.49.255.255131,070
26151.50.0.0/15151.50.0.1 to 151.51.255.254151.51.255.255131,070
27151.52.0.0/15151.52.0.1 to 151.53.255.254151.53.255.255131,070
28151.54.0.0/15151.54.0.1 to 151.55.255.254151.55.255.255131,070
29151.56.0.0/15151.56.0.1 to 151.57.255.254151.57.255.255131,070
30151.58.0.0/15151.58.0.1 to 151.59.255.254151.59.255.255131,070
31151.60.0.0/15151.60.0.1 to 151.61.255.254151.61.255.255131,070
32151.62.0.0/15151.62.0.1 to 151.63.255.254151.63.255.255131,070
33151.64.0.0/15151.64.0.1 to 151.65.255.254151.65.255.255131,070
34151.66.0.0/15151.66.0.1 to 151.67.255.254151.67.255.255131,070
35151.68.0.0/15151.68.0.1 to 151.69.255.254151.69.255.255131,070
36151.70.0.0/15151.70.0.1 to 151.71.255.254151.71.255.255131,070
37151.72.0.0/15151.72.0.1 to 151.73.255.254151.73.255.255131,070
38151.74.0.0/15151.74.0.1 to 151.75.255.254151.75.255.255131,070
39151.76.0.0/15151.76.0.1 to 151.77.255.254151.77.255.255131,070
40151.78.0.0/15151.78.0.1 to 151.79.255.254151.79.255.255131,070
41151.80.0.0/15151.80.0.1 to 151.81.255.254151.81.255.255131,070
42151.82.0.0/15151.82.0.1 to 151.83.255.254151.83.255.255131,070
43151.84.0.0/15151.84.0.1 to 151.85.255.254151.85.255.255131,070
44151.86.0.0/15151.86.0.1 to 151.87.255.254151.87.255.255131,070
45151.88.0.0/15151.88.0.1 to 151.89.255.254151.89.255.255131,070
46151.90.0.0/15151.90.0.1 to 151.91.255.254151.91.255.255131,070
47151.92.0.0/15151.92.0.1 to 151.93.255.254151.93.255.255131,070
48151.94.0.0/15151.94.0.1 to 151.95.255.254151.95.255.255131,070
49151.96.0.0/15151.96.0.1 to 151.97.255.254151.97.255.255131,070
50151.98.0.0/15151.98.0.1 to 151.99.255.254151.99.255.255131,070
51151.100.0.0/15151.100.0.1 to 151.101.255.254151.101.255.255131,070
52151.102.0.0/15151.102.0.1 to 151.103.255.254151.103.255.255131,070
53151.104.0.0/15151.104.0.1 to 151.105.255.254151.105.255.255131,070
54151.106.0.0/15151.106.0.1 to 151.107.255.254151.107.255.255131,070
55151.108.0.0/15151.108.0.1 to 151.109.255.254151.109.255.255131,070
56151.110.0.0/15151.110.0.1 to 151.111.255.254151.111.255.255131,070
57151.112.0.0/15151.112.0.1 to 151.113.255.254151.113.255.255131,070
58151.114.0.0/15151.114.0.1 to 151.115.255.254151.115.255.255131,070
59151.116.0.0/15151.116.0.1 to 151.117.255.254151.117.255.255131,070
60151.118.0.0/15151.118.0.1 to 151.119.255.254151.119.255.255131,070
61151.120.0.0/15151.120.0.1 to 151.121.255.254151.121.255.255131,070
62151.122.0.0/15151.122.0.1 to 151.123.255.254151.123.255.255131,070
63151.124.0.0/15151.124.0.1 to 151.125.255.254151.125.255.255131,070
64151.126.0.0/15151.126.0.1 to 151.127.255.254151.127.255.255131,070
65151.128.0.0/15151.128.0.1 to 151.129.255.254151.129.255.255131,070
66151.130.0.0/15151.130.0.1 to 151.131.255.254151.131.255.255131,070
67151.132.0.0/15151.132.0.1 to 151.133.255.254151.133.255.255131,070
68151.134.0.0/15151.134.0.1 to 151.135.255.254151.135.255.255131,070
69151.136.0.0/15151.136.0.1 to 151.137.255.254151.137.255.255131,070
70151.138.0.0/15151.138.0.1 to 151.139.255.254151.139.255.255131,070
71151.140.0.0/15151.140.0.1 to 151.141.255.254151.141.255.255131,070
72151.142.0.0/15151.142.0.1 to 151.143.255.254151.143.255.255131,070
73151.144.0.0/15151.144.0.1 to 151.145.255.254151.145.255.255131,070
74151.146.0.0/15151.146.0.1 to 151.147.255.254151.147.255.255131,070
75151.148.0.0/15151.148.0.1 to 151.149.255.254151.149.255.255131,070
76151.150.0.0/15151.150.0.1 to 151.151.255.254151.151.255.255131,070
77151.152.0.0/15151.152.0.1 to 151.153.255.254151.153.255.255131,070
78151.154.0.0/15151.154.0.1 to 151.155.255.254151.155.255.255131,070
79151.156.0.0/15151.156.0.1 to 151.157.255.254151.157.255.255131,070
80151.158.0.0/15151.158.0.1 to 151.159.255.254151.159.255.255131,070
81151.160.0.0/15151.160.0.1 to 151.161.255.254151.161.255.255131,070
82151.162.0.0/15151.162.0.1 to 151.163.255.254151.163.255.255131,070
83151.164.0.0/15151.164.0.1 to 151.165.255.254151.165.255.255131,070
84151.166.0.0/15151.166.0.1 to 151.167.255.254151.167.255.255131,070
85151.168.0.0/15151.168.0.1 to 151.169.255.254151.169.255.255131,070
86151.170.0.0/15151.170.0.1 to 151.171.255.254151.171.255.255131,070
87151.172.0.0/15151.172.0.1 to 151.173.255.254151.173.255.255131,070
88151.174.0.0/15151.174.0.1 to 151.175.255.254151.175.255.255131,070
89151.176.0.0/15151.176.0.1 to 151.177.255.254151.177.255.255131,070
90151.178.0.0/15151.178.0.1 to 151.179.255.254151.179.255.255131,070
91151.180.0.0/15151.180.0.1 to 151.181.255.254151.181.255.255131,070
92151.182.0.0/15151.182.0.1 to 151.183.255.254151.183.255.255131,070
93151.184.0.0/15151.184.0.1 to 151.185.255.254151.185.255.255131,070
94151.186.0.0/15151.186.0.1 to 151.187.255.254151.187.255.255131,070
95151.188.0.0/15151.188.0.1 to 151.189.255.254151.189.255.255131,070
96151.190.0.0/15151.190.0.1 to 151.191.255.254151.191.255.255131,070
97151.192.0.0/15151.192.0.1 to 151.193.255.254151.193.255.255131,070
98151.194.0.0/15151.194.0.1 to 151.195.255.254151.195.255.255131,070
99151.196.0.0/15151.196.0.1 to 151.197.255.254151.197.255.255131,070
100151.198.0.0/15151.198.0.1 to 151.199.255.254151.199.255.255131,070
101151.200.0.0/15151.200.0.1 to 151.201.255.254151.201.255.255131,070
102151.202.0.0/15151.202.0.1 to 151.203.255.254151.203.255.255131,070
103151.204.0.0/15151.204.0.1 to 151.205.255.254151.205.255.255131,070
104151.206.0.0/15151.206.0.1 to 151.207.255.254151.207.255.255131,070
105151.208.0.0/15151.208.0.1 to 151.209.255.254151.209.255.255131,070
106151.210.0.0/15151.210.0.1 to 151.211.255.254151.211.255.255131,070
107151.212.0.0/15151.212.0.1 to 151.213.255.254151.213.255.255131,070
108151.214.0.0/15151.214.0.1 to 151.215.255.254151.215.255.255131,070
109151.216.0.0/15151.216.0.1 to 151.217.255.254151.217.255.255131,070
110151.218.0.0/15151.218.0.1 to 151.219.255.254151.219.255.255131,070
111151.220.0.0/15151.220.0.1 to 151.221.255.254151.221.255.255131,070
112151.222.0.0/15151.222.0.1 to 151.223.255.254151.223.255.255131,070
113151.224.0.0/15151.224.0.1 to 151.225.255.254151.225.255.255131,070
114151.226.0.0/15151.226.0.1 to 151.227.255.254151.227.255.255131,070
115151.228.0.0/15151.228.0.1 to 151.229.255.254151.229.255.255131,070
116151.230.0.0/15151.230.0.1 to 151.231.255.254151.231.255.255131,070
117151.232.0.0/15151.232.0.1 to 151.233.255.254151.233.255.255131,070
118151.234.0.0/15151.234.0.1 to 151.235.255.254151.235.255.255131,070
119151.236.0.0/15151.236.0.1 to 151.237.255.254151.237.255.255131,070
120151.238.0.0/15151.238.0.1 to 151.239.255.254151.239.255.255131,070
121151.240.0.0/15151.240.0.1 to 151.241.255.254151.241.255.255131,070
122151.242.0.0/15151.242.0.1 to 151.243.255.254151.243.255.255131,070
123151.244.0.0/15151.244.0.1 to 151.245.255.254151.245.255.255131,070
124151.246.0.0/15151.246.0.1 to 151.247.255.254151.247.255.255131,070
125151.248.0.0/15151.248.0.1 to 151.249.255.254151.249.255.255131,070
126151.250.0.0/15151.250.0.1 to 151.251.255.254151.251.255.255131,070
127151.252.0.0/15151.252.0.1 to 151.253.255.254151.253.255.255131,070
128151.254.0.0/15151.254.0.1 to 151.255.255.254151.255.255.255131,070

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.