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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.

Network145.4.0.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
145.4.0.0
Broadcast address
145.4.31.255
First usable
145.4.0.1
Last usable
145.4.31.254
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 91040000 · Integer 2432958464 to 2432966655
Reverse DNS zones
0.4.145.in-addr.arpa
1.4.145.in-addr.arpa
2.4.145.in-addr.arpa
3.4.145.in-addr.arpa
4.4.145.in-addr.arpa
5.4.145.in-addr.arpa
6.4.145.in-addr.arpa
7.4.145.in-addr.arpa
8.4.145.in-addr.arpa
9.4.145.in-addr.arpa
10.4.145.in-addr.arpa
11.4.145.in-addr.arpa
12.4.145.in-addr.arpa
13.4.145.in-addr.arpa
14.4.145.in-addr.arpa
15.4.145.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
Address10010001.00000100.00000000.00000000145.4.0.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network10010001.00000100.00000000.00000000145.4.0.0
Broadcast10010001.00000100.00011111.11111111145.4.31.255
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)

145.4.0.0/19 makes 128 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1145.4.0.0/26145.4.0.1 to 145.4.0.62145.4.0.6362
2145.4.0.64/26145.4.0.65 to 145.4.0.126145.4.0.12762
3145.4.0.128/26145.4.0.129 to 145.4.0.190145.4.0.19162
4145.4.0.192/26145.4.0.193 to 145.4.0.254145.4.0.25562
5145.4.1.0/26145.4.1.1 to 145.4.1.62145.4.1.6362
6145.4.1.64/26145.4.1.65 to 145.4.1.126145.4.1.12762
7145.4.1.128/26145.4.1.129 to 145.4.1.190145.4.1.19162
8145.4.1.192/26145.4.1.193 to 145.4.1.254145.4.1.25562
9145.4.2.0/26145.4.2.1 to 145.4.2.62145.4.2.6362
10145.4.2.64/26145.4.2.65 to 145.4.2.126145.4.2.12762
11145.4.2.128/26145.4.2.129 to 145.4.2.190145.4.2.19162
12145.4.2.192/26145.4.2.193 to 145.4.2.254145.4.2.25562
13145.4.3.0/26145.4.3.1 to 145.4.3.62145.4.3.6362
14145.4.3.64/26145.4.3.65 to 145.4.3.126145.4.3.12762
15145.4.3.128/26145.4.3.129 to 145.4.3.190145.4.3.19162
16145.4.3.192/26145.4.3.193 to 145.4.3.254145.4.3.25562
17145.4.4.0/26145.4.4.1 to 145.4.4.62145.4.4.6362
18145.4.4.64/26145.4.4.65 to 145.4.4.126145.4.4.12762
19145.4.4.128/26145.4.4.129 to 145.4.4.190145.4.4.19162
20145.4.4.192/26145.4.4.193 to 145.4.4.254145.4.4.25562
21145.4.5.0/26145.4.5.1 to 145.4.5.62145.4.5.6362
22145.4.5.64/26145.4.5.65 to 145.4.5.126145.4.5.12762
23145.4.5.128/26145.4.5.129 to 145.4.5.190145.4.5.19162
24145.4.5.192/26145.4.5.193 to 145.4.5.254145.4.5.25562
25145.4.6.0/26145.4.6.1 to 145.4.6.62145.4.6.6362
26145.4.6.64/26145.4.6.65 to 145.4.6.126145.4.6.12762
27145.4.6.128/26145.4.6.129 to 145.4.6.190145.4.6.19162
28145.4.6.192/26145.4.6.193 to 145.4.6.254145.4.6.25562
29145.4.7.0/26145.4.7.1 to 145.4.7.62145.4.7.6362
30145.4.7.64/26145.4.7.65 to 145.4.7.126145.4.7.12762
31145.4.7.128/26145.4.7.129 to 145.4.7.190145.4.7.19162
32145.4.7.192/26145.4.7.193 to 145.4.7.254145.4.7.25562
33145.4.8.0/26145.4.8.1 to 145.4.8.62145.4.8.6362
34145.4.8.64/26145.4.8.65 to 145.4.8.126145.4.8.12762
35145.4.8.128/26145.4.8.129 to 145.4.8.190145.4.8.19162
36145.4.8.192/26145.4.8.193 to 145.4.8.254145.4.8.25562
37145.4.9.0/26145.4.9.1 to 145.4.9.62145.4.9.6362
38145.4.9.64/26145.4.9.65 to 145.4.9.126145.4.9.12762
39145.4.9.128/26145.4.9.129 to 145.4.9.190145.4.9.19162
40145.4.9.192/26145.4.9.193 to 145.4.9.254145.4.9.25562
41145.4.10.0/26145.4.10.1 to 145.4.10.62145.4.10.6362
42145.4.10.64/26145.4.10.65 to 145.4.10.126145.4.10.12762
43145.4.10.128/26145.4.10.129 to 145.4.10.190145.4.10.19162
44145.4.10.192/26145.4.10.193 to 145.4.10.254145.4.10.25562
45145.4.11.0/26145.4.11.1 to 145.4.11.62145.4.11.6362
46145.4.11.64/26145.4.11.65 to 145.4.11.126145.4.11.12762
47145.4.11.128/26145.4.11.129 to 145.4.11.190145.4.11.19162
48145.4.11.192/26145.4.11.193 to 145.4.11.254145.4.11.25562
49145.4.12.0/26145.4.12.1 to 145.4.12.62145.4.12.6362
50145.4.12.64/26145.4.12.65 to 145.4.12.126145.4.12.12762
51145.4.12.128/26145.4.12.129 to 145.4.12.190145.4.12.19162
52145.4.12.192/26145.4.12.193 to 145.4.12.254145.4.12.25562
53145.4.13.0/26145.4.13.1 to 145.4.13.62145.4.13.6362
54145.4.13.64/26145.4.13.65 to 145.4.13.126145.4.13.12762
55145.4.13.128/26145.4.13.129 to 145.4.13.190145.4.13.19162
56145.4.13.192/26145.4.13.193 to 145.4.13.254145.4.13.25562
57145.4.14.0/26145.4.14.1 to 145.4.14.62145.4.14.6362
58145.4.14.64/26145.4.14.65 to 145.4.14.126145.4.14.12762
59145.4.14.128/26145.4.14.129 to 145.4.14.190145.4.14.19162
60145.4.14.192/26145.4.14.193 to 145.4.14.254145.4.14.25562
61145.4.15.0/26145.4.15.1 to 145.4.15.62145.4.15.6362
62145.4.15.64/26145.4.15.65 to 145.4.15.126145.4.15.12762
63145.4.15.128/26145.4.15.129 to 145.4.15.190145.4.15.19162
64145.4.15.192/26145.4.15.193 to 145.4.15.254145.4.15.25562
65145.4.16.0/26145.4.16.1 to 145.4.16.62145.4.16.6362
66145.4.16.64/26145.4.16.65 to 145.4.16.126145.4.16.12762
67145.4.16.128/26145.4.16.129 to 145.4.16.190145.4.16.19162
68145.4.16.192/26145.4.16.193 to 145.4.16.254145.4.16.25562
69145.4.17.0/26145.4.17.1 to 145.4.17.62145.4.17.6362
70145.4.17.64/26145.4.17.65 to 145.4.17.126145.4.17.12762
71145.4.17.128/26145.4.17.129 to 145.4.17.190145.4.17.19162
72145.4.17.192/26145.4.17.193 to 145.4.17.254145.4.17.25562
73145.4.18.0/26145.4.18.1 to 145.4.18.62145.4.18.6362
74145.4.18.64/26145.4.18.65 to 145.4.18.126145.4.18.12762
75145.4.18.128/26145.4.18.129 to 145.4.18.190145.4.18.19162
76145.4.18.192/26145.4.18.193 to 145.4.18.254145.4.18.25562
77145.4.19.0/26145.4.19.1 to 145.4.19.62145.4.19.6362
78145.4.19.64/26145.4.19.65 to 145.4.19.126145.4.19.12762
79145.4.19.128/26145.4.19.129 to 145.4.19.190145.4.19.19162
80145.4.19.192/26145.4.19.193 to 145.4.19.254145.4.19.25562
81145.4.20.0/26145.4.20.1 to 145.4.20.62145.4.20.6362
82145.4.20.64/26145.4.20.65 to 145.4.20.126145.4.20.12762
83145.4.20.128/26145.4.20.129 to 145.4.20.190145.4.20.19162
84145.4.20.192/26145.4.20.193 to 145.4.20.254145.4.20.25562
85145.4.21.0/26145.4.21.1 to 145.4.21.62145.4.21.6362
86145.4.21.64/26145.4.21.65 to 145.4.21.126145.4.21.12762
87145.4.21.128/26145.4.21.129 to 145.4.21.190145.4.21.19162
88145.4.21.192/26145.4.21.193 to 145.4.21.254145.4.21.25562
89145.4.22.0/26145.4.22.1 to 145.4.22.62145.4.22.6362
90145.4.22.64/26145.4.22.65 to 145.4.22.126145.4.22.12762
91145.4.22.128/26145.4.22.129 to 145.4.22.190145.4.22.19162
92145.4.22.192/26145.4.22.193 to 145.4.22.254145.4.22.25562
93145.4.23.0/26145.4.23.1 to 145.4.23.62145.4.23.6362
94145.4.23.64/26145.4.23.65 to 145.4.23.126145.4.23.12762
95145.4.23.128/26145.4.23.129 to 145.4.23.190145.4.23.19162
96145.4.23.192/26145.4.23.193 to 145.4.23.254145.4.23.25562
97145.4.24.0/26145.4.24.1 to 145.4.24.62145.4.24.6362
98145.4.24.64/26145.4.24.65 to 145.4.24.126145.4.24.12762
99145.4.24.128/26145.4.24.129 to 145.4.24.190145.4.24.19162
100145.4.24.192/26145.4.24.193 to 145.4.24.254145.4.24.25562
101145.4.25.0/26145.4.25.1 to 145.4.25.62145.4.25.6362
102145.4.25.64/26145.4.25.65 to 145.4.25.126145.4.25.12762
103145.4.25.128/26145.4.25.129 to 145.4.25.190145.4.25.19162
104145.4.25.192/26145.4.25.193 to 145.4.25.254145.4.25.25562
105145.4.26.0/26145.4.26.1 to 145.4.26.62145.4.26.6362
106145.4.26.64/26145.4.26.65 to 145.4.26.126145.4.26.12762
107145.4.26.128/26145.4.26.129 to 145.4.26.190145.4.26.19162
108145.4.26.192/26145.4.26.193 to 145.4.26.254145.4.26.25562
109145.4.27.0/26145.4.27.1 to 145.4.27.62145.4.27.6362
110145.4.27.64/26145.4.27.65 to 145.4.27.126145.4.27.12762
111145.4.27.128/26145.4.27.129 to 145.4.27.190145.4.27.19162
112145.4.27.192/26145.4.27.193 to 145.4.27.254145.4.27.25562
113145.4.28.0/26145.4.28.1 to 145.4.28.62145.4.28.6362
114145.4.28.64/26145.4.28.65 to 145.4.28.126145.4.28.12762
115145.4.28.128/26145.4.28.129 to 145.4.28.190145.4.28.19162
116145.4.28.192/26145.4.28.193 to 145.4.28.254145.4.28.25562
117145.4.29.0/26145.4.29.1 to 145.4.29.62145.4.29.6362
118145.4.29.64/26145.4.29.65 to 145.4.29.126145.4.29.12762
119145.4.29.128/26145.4.29.129 to 145.4.29.190145.4.29.19162
120145.4.29.192/26145.4.29.193 to 145.4.29.254145.4.29.25562
121145.4.30.0/26145.4.30.1 to 145.4.30.62145.4.30.6362
122145.4.30.64/26145.4.30.65 to 145.4.30.126145.4.30.12762
123145.4.30.128/26145.4.30.129 to 145.4.30.190145.4.30.19162
124145.4.30.192/26145.4.30.193 to 145.4.30.254145.4.30.25562
125145.4.31.0/26145.4.31.1 to 145.4.31.62145.4.31.6362
126145.4.31.64/26145.4.31.65 to 145.4.31.126145.4.31.12762
127145.4.31.128/26145.4.31.129 to 145.4.31.190145.4.31.19162
128145.4.31.192/26145.4.31.193 to 145.4.31.254145.4.31.25562

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.