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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.

Network181.2.64.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
181.2.64.0
Broadcast address
181.2.95.255
First usable
181.2.64.1
Last usable
181.2.95.254
Usable hosts
8,190 (8,192 less the network and broadcast addresses)
Subnet mask
255.255.224.0
Wildcard mask
0.0.31.255 (Cisco ACLs, OSPF)
Prefix length
/19
Type
Public public
Old class
B (default /16)
As numbers
Hex B5024000 · Integer 3036823552 to 3036831743
Reverse DNS zones
64.2.181.in-addr.arpa
65.2.181.in-addr.arpa
66.2.181.in-addr.arpa
67.2.181.in-addr.arpa
68.2.181.in-addr.arpa
69.2.181.in-addr.arpa
70.2.181.in-addr.arpa
71.2.181.in-addr.arpa
72.2.181.in-addr.arpa
73.2.181.in-addr.arpa
74.2.181.in-addr.arpa
75.2.181.in-addr.arpa
76.2.181.in-addr.arpa
77.2.181.in-addr.arpa
78.2.181.in-addr.arpa
79.2.181.in-addr.arpa
and 16 more
/19 is not on a 8-bit boundary, so it takes 32 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10110101.00000010.01000000.00000000181.2.64.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network10110101.00000010.01000000.00000000181.2.64.0
Broadcast10110101.00000010.01011111.11111111181.2.95.255
Split into smaller subnets/26
/20 (2)/21 (4)/22 (8)/23 (16)/24 (32)/25 (64)/26 (128)/27 (256)/28 (512)/29 (1,024)/30 (2,048)/31 (4,096)

181.2.64.0/19 makes 128 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1181.2.64.0/26181.2.64.1 to 181.2.64.62181.2.64.6362
2181.2.64.64/26181.2.64.65 to 181.2.64.126181.2.64.12762
3181.2.64.128/26181.2.64.129 to 181.2.64.190181.2.64.19162
4181.2.64.192/26181.2.64.193 to 181.2.64.254181.2.64.25562
5181.2.65.0/26181.2.65.1 to 181.2.65.62181.2.65.6362
6181.2.65.64/26181.2.65.65 to 181.2.65.126181.2.65.12762
7181.2.65.128/26181.2.65.129 to 181.2.65.190181.2.65.19162
8181.2.65.192/26181.2.65.193 to 181.2.65.254181.2.65.25562
9181.2.66.0/26181.2.66.1 to 181.2.66.62181.2.66.6362
10181.2.66.64/26181.2.66.65 to 181.2.66.126181.2.66.12762
11181.2.66.128/26181.2.66.129 to 181.2.66.190181.2.66.19162
12181.2.66.192/26181.2.66.193 to 181.2.66.254181.2.66.25562
13181.2.67.0/26181.2.67.1 to 181.2.67.62181.2.67.6362
14181.2.67.64/26181.2.67.65 to 181.2.67.126181.2.67.12762
15181.2.67.128/26181.2.67.129 to 181.2.67.190181.2.67.19162
16181.2.67.192/26181.2.67.193 to 181.2.67.254181.2.67.25562
17181.2.68.0/26181.2.68.1 to 181.2.68.62181.2.68.6362
18181.2.68.64/26181.2.68.65 to 181.2.68.126181.2.68.12762
19181.2.68.128/26181.2.68.129 to 181.2.68.190181.2.68.19162
20181.2.68.192/26181.2.68.193 to 181.2.68.254181.2.68.25562
21181.2.69.0/26181.2.69.1 to 181.2.69.62181.2.69.6362
22181.2.69.64/26181.2.69.65 to 181.2.69.126181.2.69.12762
23181.2.69.128/26181.2.69.129 to 181.2.69.190181.2.69.19162
24181.2.69.192/26181.2.69.193 to 181.2.69.254181.2.69.25562
25181.2.70.0/26181.2.70.1 to 181.2.70.62181.2.70.6362
26181.2.70.64/26181.2.70.65 to 181.2.70.126181.2.70.12762
27181.2.70.128/26181.2.70.129 to 181.2.70.190181.2.70.19162
28181.2.70.192/26181.2.70.193 to 181.2.70.254181.2.70.25562
29181.2.71.0/26181.2.71.1 to 181.2.71.62181.2.71.6362
30181.2.71.64/26181.2.71.65 to 181.2.71.126181.2.71.12762
31181.2.71.128/26181.2.71.129 to 181.2.71.190181.2.71.19162
32181.2.71.192/26181.2.71.193 to 181.2.71.254181.2.71.25562
33181.2.72.0/26181.2.72.1 to 181.2.72.62181.2.72.6362
34181.2.72.64/26181.2.72.65 to 181.2.72.126181.2.72.12762
35181.2.72.128/26181.2.72.129 to 181.2.72.190181.2.72.19162
36181.2.72.192/26181.2.72.193 to 181.2.72.254181.2.72.25562
37181.2.73.0/26181.2.73.1 to 181.2.73.62181.2.73.6362
38181.2.73.64/26181.2.73.65 to 181.2.73.126181.2.73.12762
39181.2.73.128/26181.2.73.129 to 181.2.73.190181.2.73.19162
40181.2.73.192/26181.2.73.193 to 181.2.73.254181.2.73.25562
41181.2.74.0/26181.2.74.1 to 181.2.74.62181.2.74.6362
42181.2.74.64/26181.2.74.65 to 181.2.74.126181.2.74.12762
43181.2.74.128/26181.2.74.129 to 181.2.74.190181.2.74.19162
44181.2.74.192/26181.2.74.193 to 181.2.74.254181.2.74.25562
45181.2.75.0/26181.2.75.1 to 181.2.75.62181.2.75.6362
46181.2.75.64/26181.2.75.65 to 181.2.75.126181.2.75.12762
47181.2.75.128/26181.2.75.129 to 181.2.75.190181.2.75.19162
48181.2.75.192/26181.2.75.193 to 181.2.75.254181.2.75.25562
49181.2.76.0/26181.2.76.1 to 181.2.76.62181.2.76.6362
50181.2.76.64/26181.2.76.65 to 181.2.76.126181.2.76.12762
51181.2.76.128/26181.2.76.129 to 181.2.76.190181.2.76.19162
52181.2.76.192/26181.2.76.193 to 181.2.76.254181.2.76.25562
53181.2.77.0/26181.2.77.1 to 181.2.77.62181.2.77.6362
54181.2.77.64/26181.2.77.65 to 181.2.77.126181.2.77.12762
55181.2.77.128/26181.2.77.129 to 181.2.77.190181.2.77.19162
56181.2.77.192/26181.2.77.193 to 181.2.77.254181.2.77.25562
57181.2.78.0/26181.2.78.1 to 181.2.78.62181.2.78.6362
58181.2.78.64/26181.2.78.65 to 181.2.78.126181.2.78.12762
59181.2.78.128/26181.2.78.129 to 181.2.78.190181.2.78.19162
60181.2.78.192/26181.2.78.193 to 181.2.78.254181.2.78.25562
61181.2.79.0/26181.2.79.1 to 181.2.79.62181.2.79.6362
62181.2.79.64/26181.2.79.65 to 181.2.79.126181.2.79.12762
63181.2.79.128/26181.2.79.129 to 181.2.79.190181.2.79.19162
64181.2.79.192/26181.2.79.193 to 181.2.79.254181.2.79.25562
65181.2.80.0/26181.2.80.1 to 181.2.80.62181.2.80.6362
66181.2.80.64/26181.2.80.65 to 181.2.80.126181.2.80.12762
67181.2.80.128/26181.2.80.129 to 181.2.80.190181.2.80.19162
68181.2.80.192/26181.2.80.193 to 181.2.80.254181.2.80.25562
69181.2.81.0/26181.2.81.1 to 181.2.81.62181.2.81.6362
70181.2.81.64/26181.2.81.65 to 181.2.81.126181.2.81.12762
71181.2.81.128/26181.2.81.129 to 181.2.81.190181.2.81.19162
72181.2.81.192/26181.2.81.193 to 181.2.81.254181.2.81.25562
73181.2.82.0/26181.2.82.1 to 181.2.82.62181.2.82.6362
74181.2.82.64/26181.2.82.65 to 181.2.82.126181.2.82.12762
75181.2.82.128/26181.2.82.129 to 181.2.82.190181.2.82.19162
76181.2.82.192/26181.2.82.193 to 181.2.82.254181.2.82.25562
77181.2.83.0/26181.2.83.1 to 181.2.83.62181.2.83.6362
78181.2.83.64/26181.2.83.65 to 181.2.83.126181.2.83.12762
79181.2.83.128/26181.2.83.129 to 181.2.83.190181.2.83.19162
80181.2.83.192/26181.2.83.193 to 181.2.83.254181.2.83.25562
81181.2.84.0/26181.2.84.1 to 181.2.84.62181.2.84.6362
82181.2.84.64/26181.2.84.65 to 181.2.84.126181.2.84.12762
83181.2.84.128/26181.2.84.129 to 181.2.84.190181.2.84.19162
84181.2.84.192/26181.2.84.193 to 181.2.84.254181.2.84.25562
85181.2.85.0/26181.2.85.1 to 181.2.85.62181.2.85.6362
86181.2.85.64/26181.2.85.65 to 181.2.85.126181.2.85.12762
87181.2.85.128/26181.2.85.129 to 181.2.85.190181.2.85.19162
88181.2.85.192/26181.2.85.193 to 181.2.85.254181.2.85.25562
89181.2.86.0/26181.2.86.1 to 181.2.86.62181.2.86.6362
90181.2.86.64/26181.2.86.65 to 181.2.86.126181.2.86.12762
91181.2.86.128/26181.2.86.129 to 181.2.86.190181.2.86.19162
92181.2.86.192/26181.2.86.193 to 181.2.86.254181.2.86.25562
93181.2.87.0/26181.2.87.1 to 181.2.87.62181.2.87.6362
94181.2.87.64/26181.2.87.65 to 181.2.87.126181.2.87.12762
95181.2.87.128/26181.2.87.129 to 181.2.87.190181.2.87.19162
96181.2.87.192/26181.2.87.193 to 181.2.87.254181.2.87.25562
97181.2.88.0/26181.2.88.1 to 181.2.88.62181.2.88.6362
98181.2.88.64/26181.2.88.65 to 181.2.88.126181.2.88.12762
99181.2.88.128/26181.2.88.129 to 181.2.88.190181.2.88.19162
100181.2.88.192/26181.2.88.193 to 181.2.88.254181.2.88.25562
101181.2.89.0/26181.2.89.1 to 181.2.89.62181.2.89.6362
102181.2.89.64/26181.2.89.65 to 181.2.89.126181.2.89.12762
103181.2.89.128/26181.2.89.129 to 181.2.89.190181.2.89.19162
104181.2.89.192/26181.2.89.193 to 181.2.89.254181.2.89.25562
105181.2.90.0/26181.2.90.1 to 181.2.90.62181.2.90.6362
106181.2.90.64/26181.2.90.65 to 181.2.90.126181.2.90.12762
107181.2.90.128/26181.2.90.129 to 181.2.90.190181.2.90.19162
108181.2.90.192/26181.2.90.193 to 181.2.90.254181.2.90.25562
109181.2.91.0/26181.2.91.1 to 181.2.91.62181.2.91.6362
110181.2.91.64/26181.2.91.65 to 181.2.91.126181.2.91.12762
111181.2.91.128/26181.2.91.129 to 181.2.91.190181.2.91.19162
112181.2.91.192/26181.2.91.193 to 181.2.91.254181.2.91.25562
113181.2.92.0/26181.2.92.1 to 181.2.92.62181.2.92.6362
114181.2.92.64/26181.2.92.65 to 181.2.92.126181.2.92.12762
115181.2.92.128/26181.2.92.129 to 181.2.92.190181.2.92.19162
116181.2.92.192/26181.2.92.193 to 181.2.92.254181.2.92.25562
117181.2.93.0/26181.2.93.1 to 181.2.93.62181.2.93.6362
118181.2.93.64/26181.2.93.65 to 181.2.93.126181.2.93.12762
119181.2.93.128/26181.2.93.129 to 181.2.93.190181.2.93.19162
120181.2.93.192/26181.2.93.193 to 181.2.93.254181.2.93.25562
121181.2.94.0/26181.2.94.1 to 181.2.94.62181.2.94.6362
122181.2.94.64/26181.2.94.65 to 181.2.94.126181.2.94.12762
123181.2.94.128/26181.2.94.129 to 181.2.94.190181.2.94.19162
124181.2.94.192/26181.2.94.193 to 181.2.94.254181.2.94.25562
125181.2.95.0/26181.2.95.1 to 181.2.95.62181.2.95.6362
126181.2.95.64/26181.2.95.65 to 181.2.95.126181.2.95.12762
127181.2.95.128/26181.2.95.129 to 181.2.95.190181.2.95.19162
128181.2.95.192/26181.2.95.193 to 181.2.95.254181.2.95.25562

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.