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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.

Network241.128.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
241.128.0.0
Broadcast address
241.255.255.255
First usable
241.128.0.1
Last usable
241.255.255.254
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
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F1800000 · Integer 4051697664 to 4060086271
Reverse DNS zones
128.241.in-addr.arpa
129.241.in-addr.arpa
130.241.in-addr.arpa
131.241.in-addr.arpa
132.241.in-addr.arpa
133.241.in-addr.arpa
134.241.in-addr.arpa
135.241.in-addr.arpa
136.241.in-addr.arpa
137.241.in-addr.arpa
138.241.in-addr.arpa
139.241.in-addr.arpa
140.241.in-addr.arpa
141.241.in-addr.arpa
142.241.in-addr.arpa
143.241.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
Address11110001.10000000.00000000.00000000241.128.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network11110001.10000000.00000000.00000000241.128.0.0
Broadcast11110001.11111111.11111111.11111111241.255.255.255
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)

241.128.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1241.128.0.0/16241.128.0.1 to 241.128.255.254241.128.255.25565,534
2241.129.0.0/16241.129.0.1 to 241.129.255.254241.129.255.25565,534
3241.130.0.0/16241.130.0.1 to 241.130.255.254241.130.255.25565,534
4241.131.0.0/16241.131.0.1 to 241.131.255.254241.131.255.25565,534
5241.132.0.0/16241.132.0.1 to 241.132.255.254241.132.255.25565,534
6241.133.0.0/16241.133.0.1 to 241.133.255.254241.133.255.25565,534
7241.134.0.0/16241.134.0.1 to 241.134.255.254241.134.255.25565,534
8241.135.0.0/16241.135.0.1 to 241.135.255.254241.135.255.25565,534
9241.136.0.0/16241.136.0.1 to 241.136.255.254241.136.255.25565,534
10241.137.0.0/16241.137.0.1 to 241.137.255.254241.137.255.25565,534
11241.138.0.0/16241.138.0.1 to 241.138.255.254241.138.255.25565,534
12241.139.0.0/16241.139.0.1 to 241.139.255.254241.139.255.25565,534
13241.140.0.0/16241.140.0.1 to 241.140.255.254241.140.255.25565,534
14241.141.0.0/16241.141.0.1 to 241.141.255.254241.141.255.25565,534
15241.142.0.0/16241.142.0.1 to 241.142.255.254241.142.255.25565,534
16241.143.0.0/16241.143.0.1 to 241.143.255.254241.143.255.25565,534
17241.144.0.0/16241.144.0.1 to 241.144.255.254241.144.255.25565,534
18241.145.0.0/16241.145.0.1 to 241.145.255.254241.145.255.25565,534
19241.146.0.0/16241.146.0.1 to 241.146.255.254241.146.255.25565,534
20241.147.0.0/16241.147.0.1 to 241.147.255.254241.147.255.25565,534
21241.148.0.0/16241.148.0.1 to 241.148.255.254241.148.255.25565,534
22241.149.0.0/16241.149.0.1 to 241.149.255.254241.149.255.25565,534
23241.150.0.0/16241.150.0.1 to 241.150.255.254241.150.255.25565,534
24241.151.0.0/16241.151.0.1 to 241.151.255.254241.151.255.25565,534
25241.152.0.0/16241.152.0.1 to 241.152.255.254241.152.255.25565,534
26241.153.0.0/16241.153.0.1 to 241.153.255.254241.153.255.25565,534
27241.154.0.0/16241.154.0.1 to 241.154.255.254241.154.255.25565,534
28241.155.0.0/16241.155.0.1 to 241.155.255.254241.155.255.25565,534
29241.156.0.0/16241.156.0.1 to 241.156.255.254241.156.255.25565,534
30241.157.0.0/16241.157.0.1 to 241.157.255.254241.157.255.25565,534
31241.158.0.0/16241.158.0.1 to 241.158.255.254241.158.255.25565,534
32241.159.0.0/16241.159.0.1 to 241.159.255.254241.159.255.25565,534
33241.160.0.0/16241.160.0.1 to 241.160.255.254241.160.255.25565,534
34241.161.0.0/16241.161.0.1 to 241.161.255.254241.161.255.25565,534
35241.162.0.0/16241.162.0.1 to 241.162.255.254241.162.255.25565,534
36241.163.0.0/16241.163.0.1 to 241.163.255.254241.163.255.25565,534
37241.164.0.0/16241.164.0.1 to 241.164.255.254241.164.255.25565,534
38241.165.0.0/16241.165.0.1 to 241.165.255.254241.165.255.25565,534
39241.166.0.0/16241.166.0.1 to 241.166.255.254241.166.255.25565,534
40241.167.0.0/16241.167.0.1 to 241.167.255.254241.167.255.25565,534
41241.168.0.0/16241.168.0.1 to 241.168.255.254241.168.255.25565,534
42241.169.0.0/16241.169.0.1 to 241.169.255.254241.169.255.25565,534
43241.170.0.0/16241.170.0.1 to 241.170.255.254241.170.255.25565,534
44241.171.0.0/16241.171.0.1 to 241.171.255.254241.171.255.25565,534
45241.172.0.0/16241.172.0.1 to 241.172.255.254241.172.255.25565,534
46241.173.0.0/16241.173.0.1 to 241.173.255.254241.173.255.25565,534
47241.174.0.0/16241.174.0.1 to 241.174.255.254241.174.255.25565,534
48241.175.0.0/16241.175.0.1 to 241.175.255.254241.175.255.25565,534
49241.176.0.0/16241.176.0.1 to 241.176.255.254241.176.255.25565,534
50241.177.0.0/16241.177.0.1 to 241.177.255.254241.177.255.25565,534
51241.178.0.0/16241.178.0.1 to 241.178.255.254241.178.255.25565,534
52241.179.0.0/16241.179.0.1 to 241.179.255.254241.179.255.25565,534
53241.180.0.0/16241.180.0.1 to 241.180.255.254241.180.255.25565,534
54241.181.0.0/16241.181.0.1 to 241.181.255.254241.181.255.25565,534
55241.182.0.0/16241.182.0.1 to 241.182.255.254241.182.255.25565,534
56241.183.0.0/16241.183.0.1 to 241.183.255.254241.183.255.25565,534
57241.184.0.0/16241.184.0.1 to 241.184.255.254241.184.255.25565,534
58241.185.0.0/16241.185.0.1 to 241.185.255.254241.185.255.25565,534
59241.186.0.0/16241.186.0.1 to 241.186.255.254241.186.255.25565,534
60241.187.0.0/16241.187.0.1 to 241.187.255.254241.187.255.25565,534
61241.188.0.0/16241.188.0.1 to 241.188.255.254241.188.255.25565,534
62241.189.0.0/16241.189.0.1 to 241.189.255.254241.189.255.25565,534
63241.190.0.0/16241.190.0.1 to 241.190.255.254241.190.255.25565,534
64241.191.0.0/16241.191.0.1 to 241.191.255.254241.191.255.25565,534
65241.192.0.0/16241.192.0.1 to 241.192.255.254241.192.255.25565,534
66241.193.0.0/16241.193.0.1 to 241.193.255.254241.193.255.25565,534
67241.194.0.0/16241.194.0.1 to 241.194.255.254241.194.255.25565,534
68241.195.0.0/16241.195.0.1 to 241.195.255.254241.195.255.25565,534
69241.196.0.0/16241.196.0.1 to 241.196.255.254241.196.255.25565,534
70241.197.0.0/16241.197.0.1 to 241.197.255.254241.197.255.25565,534
71241.198.0.0/16241.198.0.1 to 241.198.255.254241.198.255.25565,534
72241.199.0.0/16241.199.0.1 to 241.199.255.254241.199.255.25565,534
73241.200.0.0/16241.200.0.1 to 241.200.255.254241.200.255.25565,534
74241.201.0.0/16241.201.0.1 to 241.201.255.254241.201.255.25565,534
75241.202.0.0/16241.202.0.1 to 241.202.255.254241.202.255.25565,534
76241.203.0.0/16241.203.0.1 to 241.203.255.254241.203.255.25565,534
77241.204.0.0/16241.204.0.1 to 241.204.255.254241.204.255.25565,534
78241.205.0.0/16241.205.0.1 to 241.205.255.254241.205.255.25565,534
79241.206.0.0/16241.206.0.1 to 241.206.255.254241.206.255.25565,534
80241.207.0.0/16241.207.0.1 to 241.207.255.254241.207.255.25565,534
81241.208.0.0/16241.208.0.1 to 241.208.255.254241.208.255.25565,534
82241.209.0.0/16241.209.0.1 to 241.209.255.254241.209.255.25565,534
83241.210.0.0/16241.210.0.1 to 241.210.255.254241.210.255.25565,534
84241.211.0.0/16241.211.0.1 to 241.211.255.254241.211.255.25565,534
85241.212.0.0/16241.212.0.1 to 241.212.255.254241.212.255.25565,534
86241.213.0.0/16241.213.0.1 to 241.213.255.254241.213.255.25565,534
87241.214.0.0/16241.214.0.1 to 241.214.255.254241.214.255.25565,534
88241.215.0.0/16241.215.0.1 to 241.215.255.254241.215.255.25565,534
89241.216.0.0/16241.216.0.1 to 241.216.255.254241.216.255.25565,534
90241.217.0.0/16241.217.0.1 to 241.217.255.254241.217.255.25565,534
91241.218.0.0/16241.218.0.1 to 241.218.255.254241.218.255.25565,534
92241.219.0.0/16241.219.0.1 to 241.219.255.254241.219.255.25565,534
93241.220.0.0/16241.220.0.1 to 241.220.255.254241.220.255.25565,534
94241.221.0.0/16241.221.0.1 to 241.221.255.254241.221.255.25565,534
95241.222.0.0/16241.222.0.1 to 241.222.255.254241.222.255.25565,534
96241.223.0.0/16241.223.0.1 to 241.223.255.254241.223.255.25565,534
97241.224.0.0/16241.224.0.1 to 241.224.255.254241.224.255.25565,534
98241.225.0.0/16241.225.0.1 to 241.225.255.254241.225.255.25565,534
99241.226.0.0/16241.226.0.1 to 241.226.255.254241.226.255.25565,534
100241.227.0.0/16241.227.0.1 to 241.227.255.254241.227.255.25565,534
101241.228.0.0/16241.228.0.1 to 241.228.255.254241.228.255.25565,534
102241.229.0.0/16241.229.0.1 to 241.229.255.254241.229.255.25565,534
103241.230.0.0/16241.230.0.1 to 241.230.255.254241.230.255.25565,534
104241.231.0.0/16241.231.0.1 to 241.231.255.254241.231.255.25565,534
105241.232.0.0/16241.232.0.1 to 241.232.255.254241.232.255.25565,534
106241.233.0.0/16241.233.0.1 to 241.233.255.254241.233.255.25565,534
107241.234.0.0/16241.234.0.1 to 241.234.255.254241.234.255.25565,534
108241.235.0.0/16241.235.0.1 to 241.235.255.254241.235.255.25565,534
109241.236.0.0/16241.236.0.1 to 241.236.255.254241.236.255.25565,534
110241.237.0.0/16241.237.0.1 to 241.237.255.254241.237.255.25565,534
111241.238.0.0/16241.238.0.1 to 241.238.255.254241.238.255.25565,534
112241.239.0.0/16241.239.0.1 to 241.239.255.254241.239.255.25565,534
113241.240.0.0/16241.240.0.1 to 241.240.255.254241.240.255.25565,534
114241.241.0.0/16241.241.0.1 to 241.241.255.254241.241.255.25565,534
115241.242.0.0/16241.242.0.1 to 241.242.255.254241.242.255.25565,534
116241.243.0.0/16241.243.0.1 to 241.243.255.254241.243.255.25565,534
117241.244.0.0/16241.244.0.1 to 241.244.255.254241.244.255.25565,534
118241.245.0.0/16241.245.0.1 to 241.245.255.254241.245.255.25565,534
119241.246.0.0/16241.246.0.1 to 241.246.255.254241.246.255.25565,534
120241.247.0.0/16241.247.0.1 to 241.247.255.254241.247.255.25565,534
121241.248.0.0/16241.248.0.1 to 241.248.255.254241.248.255.25565,534
122241.249.0.0/16241.249.0.1 to 241.249.255.254241.249.255.25565,534
123241.250.0.0/16241.250.0.1 to 241.250.255.254241.250.255.25565,534
124241.251.0.0/16241.251.0.1 to 241.251.255.254241.251.255.25565,534
125241.252.0.0/16241.252.0.1 to 241.252.255.254241.252.255.25565,534
126241.253.0.0/16241.253.0.1 to 241.253.255.254241.253.255.25565,534
127241.254.0.0/16241.254.0.1 to 241.254.255.254241.254.255.25565,534
128241.255.0.0/16241.255.0.1 to 241.255.255.254241.255.255.25565,534

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.