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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.

Network231.1.32.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
231.1.32.0
Broadcast address
231.1.63.255
First usable
231.1.32.1
Last usable
231.1.63.254
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
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex E7012000 · Integer 3875610624 to 3875618815
Reverse DNS zones
32.1.231.in-addr.arpa
33.1.231.in-addr.arpa
34.1.231.in-addr.arpa
35.1.231.in-addr.arpa
36.1.231.in-addr.arpa
37.1.231.in-addr.arpa
38.1.231.in-addr.arpa
39.1.231.in-addr.arpa
40.1.231.in-addr.arpa
41.1.231.in-addr.arpa
42.1.231.in-addr.arpa
43.1.231.in-addr.arpa
44.1.231.in-addr.arpa
45.1.231.in-addr.arpa
46.1.231.in-addr.arpa
47.1.231.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
Address11100111.00000001.00100000.00000000231.1.32.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network11100111.00000001.00100000.00000000231.1.32.0
Broadcast11100111.00000001.00111111.11111111231.1.63.255
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)

231.1.32.0/19 makes 128 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1231.1.32.0/26231.1.32.1 to 231.1.32.62231.1.32.6362
2231.1.32.64/26231.1.32.65 to 231.1.32.126231.1.32.12762
3231.1.32.128/26231.1.32.129 to 231.1.32.190231.1.32.19162
4231.1.32.192/26231.1.32.193 to 231.1.32.254231.1.32.25562
5231.1.33.0/26231.1.33.1 to 231.1.33.62231.1.33.6362
6231.1.33.64/26231.1.33.65 to 231.1.33.126231.1.33.12762
7231.1.33.128/26231.1.33.129 to 231.1.33.190231.1.33.19162
8231.1.33.192/26231.1.33.193 to 231.1.33.254231.1.33.25562
9231.1.34.0/26231.1.34.1 to 231.1.34.62231.1.34.6362
10231.1.34.64/26231.1.34.65 to 231.1.34.126231.1.34.12762
11231.1.34.128/26231.1.34.129 to 231.1.34.190231.1.34.19162
12231.1.34.192/26231.1.34.193 to 231.1.34.254231.1.34.25562
13231.1.35.0/26231.1.35.1 to 231.1.35.62231.1.35.6362
14231.1.35.64/26231.1.35.65 to 231.1.35.126231.1.35.12762
15231.1.35.128/26231.1.35.129 to 231.1.35.190231.1.35.19162
16231.1.35.192/26231.1.35.193 to 231.1.35.254231.1.35.25562
17231.1.36.0/26231.1.36.1 to 231.1.36.62231.1.36.6362
18231.1.36.64/26231.1.36.65 to 231.1.36.126231.1.36.12762
19231.1.36.128/26231.1.36.129 to 231.1.36.190231.1.36.19162
20231.1.36.192/26231.1.36.193 to 231.1.36.254231.1.36.25562
21231.1.37.0/26231.1.37.1 to 231.1.37.62231.1.37.6362
22231.1.37.64/26231.1.37.65 to 231.1.37.126231.1.37.12762
23231.1.37.128/26231.1.37.129 to 231.1.37.190231.1.37.19162
24231.1.37.192/26231.1.37.193 to 231.1.37.254231.1.37.25562
25231.1.38.0/26231.1.38.1 to 231.1.38.62231.1.38.6362
26231.1.38.64/26231.1.38.65 to 231.1.38.126231.1.38.12762
27231.1.38.128/26231.1.38.129 to 231.1.38.190231.1.38.19162
28231.1.38.192/26231.1.38.193 to 231.1.38.254231.1.38.25562
29231.1.39.0/26231.1.39.1 to 231.1.39.62231.1.39.6362
30231.1.39.64/26231.1.39.65 to 231.1.39.126231.1.39.12762
31231.1.39.128/26231.1.39.129 to 231.1.39.190231.1.39.19162
32231.1.39.192/26231.1.39.193 to 231.1.39.254231.1.39.25562
33231.1.40.0/26231.1.40.1 to 231.1.40.62231.1.40.6362
34231.1.40.64/26231.1.40.65 to 231.1.40.126231.1.40.12762
35231.1.40.128/26231.1.40.129 to 231.1.40.190231.1.40.19162
36231.1.40.192/26231.1.40.193 to 231.1.40.254231.1.40.25562
37231.1.41.0/26231.1.41.1 to 231.1.41.62231.1.41.6362
38231.1.41.64/26231.1.41.65 to 231.1.41.126231.1.41.12762
39231.1.41.128/26231.1.41.129 to 231.1.41.190231.1.41.19162
40231.1.41.192/26231.1.41.193 to 231.1.41.254231.1.41.25562
41231.1.42.0/26231.1.42.1 to 231.1.42.62231.1.42.6362
42231.1.42.64/26231.1.42.65 to 231.1.42.126231.1.42.12762
43231.1.42.128/26231.1.42.129 to 231.1.42.190231.1.42.19162
44231.1.42.192/26231.1.42.193 to 231.1.42.254231.1.42.25562
45231.1.43.0/26231.1.43.1 to 231.1.43.62231.1.43.6362
46231.1.43.64/26231.1.43.65 to 231.1.43.126231.1.43.12762
47231.1.43.128/26231.1.43.129 to 231.1.43.190231.1.43.19162
48231.1.43.192/26231.1.43.193 to 231.1.43.254231.1.43.25562
49231.1.44.0/26231.1.44.1 to 231.1.44.62231.1.44.6362
50231.1.44.64/26231.1.44.65 to 231.1.44.126231.1.44.12762
51231.1.44.128/26231.1.44.129 to 231.1.44.190231.1.44.19162
52231.1.44.192/26231.1.44.193 to 231.1.44.254231.1.44.25562
53231.1.45.0/26231.1.45.1 to 231.1.45.62231.1.45.6362
54231.1.45.64/26231.1.45.65 to 231.1.45.126231.1.45.12762
55231.1.45.128/26231.1.45.129 to 231.1.45.190231.1.45.19162
56231.1.45.192/26231.1.45.193 to 231.1.45.254231.1.45.25562
57231.1.46.0/26231.1.46.1 to 231.1.46.62231.1.46.6362
58231.1.46.64/26231.1.46.65 to 231.1.46.126231.1.46.12762
59231.1.46.128/26231.1.46.129 to 231.1.46.190231.1.46.19162
60231.1.46.192/26231.1.46.193 to 231.1.46.254231.1.46.25562
61231.1.47.0/26231.1.47.1 to 231.1.47.62231.1.47.6362
62231.1.47.64/26231.1.47.65 to 231.1.47.126231.1.47.12762
63231.1.47.128/26231.1.47.129 to 231.1.47.190231.1.47.19162
64231.1.47.192/26231.1.47.193 to 231.1.47.254231.1.47.25562
65231.1.48.0/26231.1.48.1 to 231.1.48.62231.1.48.6362
66231.1.48.64/26231.1.48.65 to 231.1.48.126231.1.48.12762
67231.1.48.128/26231.1.48.129 to 231.1.48.190231.1.48.19162
68231.1.48.192/26231.1.48.193 to 231.1.48.254231.1.48.25562
69231.1.49.0/26231.1.49.1 to 231.1.49.62231.1.49.6362
70231.1.49.64/26231.1.49.65 to 231.1.49.126231.1.49.12762
71231.1.49.128/26231.1.49.129 to 231.1.49.190231.1.49.19162
72231.1.49.192/26231.1.49.193 to 231.1.49.254231.1.49.25562
73231.1.50.0/26231.1.50.1 to 231.1.50.62231.1.50.6362
74231.1.50.64/26231.1.50.65 to 231.1.50.126231.1.50.12762
75231.1.50.128/26231.1.50.129 to 231.1.50.190231.1.50.19162
76231.1.50.192/26231.1.50.193 to 231.1.50.254231.1.50.25562
77231.1.51.0/26231.1.51.1 to 231.1.51.62231.1.51.6362
78231.1.51.64/26231.1.51.65 to 231.1.51.126231.1.51.12762
79231.1.51.128/26231.1.51.129 to 231.1.51.190231.1.51.19162
80231.1.51.192/26231.1.51.193 to 231.1.51.254231.1.51.25562
81231.1.52.0/26231.1.52.1 to 231.1.52.62231.1.52.6362
82231.1.52.64/26231.1.52.65 to 231.1.52.126231.1.52.12762
83231.1.52.128/26231.1.52.129 to 231.1.52.190231.1.52.19162
84231.1.52.192/26231.1.52.193 to 231.1.52.254231.1.52.25562
85231.1.53.0/26231.1.53.1 to 231.1.53.62231.1.53.6362
86231.1.53.64/26231.1.53.65 to 231.1.53.126231.1.53.12762
87231.1.53.128/26231.1.53.129 to 231.1.53.190231.1.53.19162
88231.1.53.192/26231.1.53.193 to 231.1.53.254231.1.53.25562
89231.1.54.0/26231.1.54.1 to 231.1.54.62231.1.54.6362
90231.1.54.64/26231.1.54.65 to 231.1.54.126231.1.54.12762
91231.1.54.128/26231.1.54.129 to 231.1.54.190231.1.54.19162
92231.1.54.192/26231.1.54.193 to 231.1.54.254231.1.54.25562
93231.1.55.0/26231.1.55.1 to 231.1.55.62231.1.55.6362
94231.1.55.64/26231.1.55.65 to 231.1.55.126231.1.55.12762
95231.1.55.128/26231.1.55.129 to 231.1.55.190231.1.55.19162
96231.1.55.192/26231.1.55.193 to 231.1.55.254231.1.55.25562
97231.1.56.0/26231.1.56.1 to 231.1.56.62231.1.56.6362
98231.1.56.64/26231.1.56.65 to 231.1.56.126231.1.56.12762
99231.1.56.128/26231.1.56.129 to 231.1.56.190231.1.56.19162
100231.1.56.192/26231.1.56.193 to 231.1.56.254231.1.56.25562
101231.1.57.0/26231.1.57.1 to 231.1.57.62231.1.57.6362
102231.1.57.64/26231.1.57.65 to 231.1.57.126231.1.57.12762
103231.1.57.128/26231.1.57.129 to 231.1.57.190231.1.57.19162
104231.1.57.192/26231.1.57.193 to 231.1.57.254231.1.57.25562
105231.1.58.0/26231.1.58.1 to 231.1.58.62231.1.58.6362
106231.1.58.64/26231.1.58.65 to 231.1.58.126231.1.58.12762
107231.1.58.128/26231.1.58.129 to 231.1.58.190231.1.58.19162
108231.1.58.192/26231.1.58.193 to 231.1.58.254231.1.58.25562
109231.1.59.0/26231.1.59.1 to 231.1.59.62231.1.59.6362
110231.1.59.64/26231.1.59.65 to 231.1.59.126231.1.59.12762
111231.1.59.128/26231.1.59.129 to 231.1.59.190231.1.59.19162
112231.1.59.192/26231.1.59.193 to 231.1.59.254231.1.59.25562
113231.1.60.0/26231.1.60.1 to 231.1.60.62231.1.60.6362
114231.1.60.64/26231.1.60.65 to 231.1.60.126231.1.60.12762
115231.1.60.128/26231.1.60.129 to 231.1.60.190231.1.60.19162
116231.1.60.192/26231.1.60.193 to 231.1.60.254231.1.60.25562
117231.1.61.0/26231.1.61.1 to 231.1.61.62231.1.61.6362
118231.1.61.64/26231.1.61.65 to 231.1.61.126231.1.61.12762
119231.1.61.128/26231.1.61.129 to 231.1.61.190231.1.61.19162
120231.1.61.192/26231.1.61.193 to 231.1.61.254231.1.61.25562
121231.1.62.0/26231.1.62.1 to 231.1.62.62231.1.62.6362
122231.1.62.64/26231.1.62.65 to 231.1.62.126231.1.62.12762
123231.1.62.128/26231.1.62.129 to 231.1.62.190231.1.62.19162
124231.1.62.192/26231.1.62.193 to 231.1.62.254231.1.62.25562
125231.1.63.0/26231.1.63.1 to 231.1.63.62231.1.63.6362
126231.1.63.64/26231.1.63.65 to 231.1.63.126231.1.63.12762
127231.1.63.128/26231.1.63.129 to 231.1.63.190231.1.63.19162
128231.1.63.192/26231.1.63.193 to 231.1.63.254231.1.63.25562

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.