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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.

Network243.0.32.0/19
Usable hosts8,190
Subnet mask255.255.224.0
Addresses8,192
Network address
243.0.32.0
Broadcast address
243.0.63.255
First usable
243.0.32.1
Last usable
243.0.63.254
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
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F3002000 · Integer 4076871680 to 4076879871
Reverse DNS zones
32.0.243.in-addr.arpa
33.0.243.in-addr.arpa
34.0.243.in-addr.arpa
35.0.243.in-addr.arpa
36.0.243.in-addr.arpa
37.0.243.in-addr.arpa
38.0.243.in-addr.arpa
39.0.243.in-addr.arpa
40.0.243.in-addr.arpa
41.0.243.in-addr.arpa
42.0.243.in-addr.arpa
43.0.243.in-addr.arpa
44.0.243.in-addr.arpa
45.0.243.in-addr.arpa
46.0.243.in-addr.arpa
47.0.243.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
Address11110011.00000000.00100000.00000000243.0.32.0
Subnet mask11111111.11111111.11100000.00000000255.255.224.0
Network11110011.00000000.00100000.00000000243.0.32.0
Broadcast11110011.00000000.00111111.11111111243.0.63.255
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)

243.0.32.0/19 makes 128 subnets of /26.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1243.0.32.0/26243.0.32.1 to 243.0.32.62243.0.32.6362
2243.0.32.64/26243.0.32.65 to 243.0.32.126243.0.32.12762
3243.0.32.128/26243.0.32.129 to 243.0.32.190243.0.32.19162
4243.0.32.192/26243.0.32.193 to 243.0.32.254243.0.32.25562
5243.0.33.0/26243.0.33.1 to 243.0.33.62243.0.33.6362
6243.0.33.64/26243.0.33.65 to 243.0.33.126243.0.33.12762
7243.0.33.128/26243.0.33.129 to 243.0.33.190243.0.33.19162
8243.0.33.192/26243.0.33.193 to 243.0.33.254243.0.33.25562
9243.0.34.0/26243.0.34.1 to 243.0.34.62243.0.34.6362
10243.0.34.64/26243.0.34.65 to 243.0.34.126243.0.34.12762
11243.0.34.128/26243.0.34.129 to 243.0.34.190243.0.34.19162
12243.0.34.192/26243.0.34.193 to 243.0.34.254243.0.34.25562
13243.0.35.0/26243.0.35.1 to 243.0.35.62243.0.35.6362
14243.0.35.64/26243.0.35.65 to 243.0.35.126243.0.35.12762
15243.0.35.128/26243.0.35.129 to 243.0.35.190243.0.35.19162
16243.0.35.192/26243.0.35.193 to 243.0.35.254243.0.35.25562
17243.0.36.0/26243.0.36.1 to 243.0.36.62243.0.36.6362
18243.0.36.64/26243.0.36.65 to 243.0.36.126243.0.36.12762
19243.0.36.128/26243.0.36.129 to 243.0.36.190243.0.36.19162
20243.0.36.192/26243.0.36.193 to 243.0.36.254243.0.36.25562
21243.0.37.0/26243.0.37.1 to 243.0.37.62243.0.37.6362
22243.0.37.64/26243.0.37.65 to 243.0.37.126243.0.37.12762
23243.0.37.128/26243.0.37.129 to 243.0.37.190243.0.37.19162
24243.0.37.192/26243.0.37.193 to 243.0.37.254243.0.37.25562
25243.0.38.0/26243.0.38.1 to 243.0.38.62243.0.38.6362
26243.0.38.64/26243.0.38.65 to 243.0.38.126243.0.38.12762
27243.0.38.128/26243.0.38.129 to 243.0.38.190243.0.38.19162
28243.0.38.192/26243.0.38.193 to 243.0.38.254243.0.38.25562
29243.0.39.0/26243.0.39.1 to 243.0.39.62243.0.39.6362
30243.0.39.64/26243.0.39.65 to 243.0.39.126243.0.39.12762
31243.0.39.128/26243.0.39.129 to 243.0.39.190243.0.39.19162
32243.0.39.192/26243.0.39.193 to 243.0.39.254243.0.39.25562
33243.0.40.0/26243.0.40.1 to 243.0.40.62243.0.40.6362
34243.0.40.64/26243.0.40.65 to 243.0.40.126243.0.40.12762
35243.0.40.128/26243.0.40.129 to 243.0.40.190243.0.40.19162
36243.0.40.192/26243.0.40.193 to 243.0.40.254243.0.40.25562
37243.0.41.0/26243.0.41.1 to 243.0.41.62243.0.41.6362
38243.0.41.64/26243.0.41.65 to 243.0.41.126243.0.41.12762
39243.0.41.128/26243.0.41.129 to 243.0.41.190243.0.41.19162
40243.0.41.192/26243.0.41.193 to 243.0.41.254243.0.41.25562
41243.0.42.0/26243.0.42.1 to 243.0.42.62243.0.42.6362
42243.0.42.64/26243.0.42.65 to 243.0.42.126243.0.42.12762
43243.0.42.128/26243.0.42.129 to 243.0.42.190243.0.42.19162
44243.0.42.192/26243.0.42.193 to 243.0.42.254243.0.42.25562
45243.0.43.0/26243.0.43.1 to 243.0.43.62243.0.43.6362
46243.0.43.64/26243.0.43.65 to 243.0.43.126243.0.43.12762
47243.0.43.128/26243.0.43.129 to 243.0.43.190243.0.43.19162
48243.0.43.192/26243.0.43.193 to 243.0.43.254243.0.43.25562
49243.0.44.0/26243.0.44.1 to 243.0.44.62243.0.44.6362
50243.0.44.64/26243.0.44.65 to 243.0.44.126243.0.44.12762
51243.0.44.128/26243.0.44.129 to 243.0.44.190243.0.44.19162
52243.0.44.192/26243.0.44.193 to 243.0.44.254243.0.44.25562
53243.0.45.0/26243.0.45.1 to 243.0.45.62243.0.45.6362
54243.0.45.64/26243.0.45.65 to 243.0.45.126243.0.45.12762
55243.0.45.128/26243.0.45.129 to 243.0.45.190243.0.45.19162
56243.0.45.192/26243.0.45.193 to 243.0.45.254243.0.45.25562
57243.0.46.0/26243.0.46.1 to 243.0.46.62243.0.46.6362
58243.0.46.64/26243.0.46.65 to 243.0.46.126243.0.46.12762
59243.0.46.128/26243.0.46.129 to 243.0.46.190243.0.46.19162
60243.0.46.192/26243.0.46.193 to 243.0.46.254243.0.46.25562
61243.0.47.0/26243.0.47.1 to 243.0.47.62243.0.47.6362
62243.0.47.64/26243.0.47.65 to 243.0.47.126243.0.47.12762
63243.0.47.128/26243.0.47.129 to 243.0.47.190243.0.47.19162
64243.0.47.192/26243.0.47.193 to 243.0.47.254243.0.47.25562
65243.0.48.0/26243.0.48.1 to 243.0.48.62243.0.48.6362
66243.0.48.64/26243.0.48.65 to 243.0.48.126243.0.48.12762
67243.0.48.128/26243.0.48.129 to 243.0.48.190243.0.48.19162
68243.0.48.192/26243.0.48.193 to 243.0.48.254243.0.48.25562
69243.0.49.0/26243.0.49.1 to 243.0.49.62243.0.49.6362
70243.0.49.64/26243.0.49.65 to 243.0.49.126243.0.49.12762
71243.0.49.128/26243.0.49.129 to 243.0.49.190243.0.49.19162
72243.0.49.192/26243.0.49.193 to 243.0.49.254243.0.49.25562
73243.0.50.0/26243.0.50.1 to 243.0.50.62243.0.50.6362
74243.0.50.64/26243.0.50.65 to 243.0.50.126243.0.50.12762
75243.0.50.128/26243.0.50.129 to 243.0.50.190243.0.50.19162
76243.0.50.192/26243.0.50.193 to 243.0.50.254243.0.50.25562
77243.0.51.0/26243.0.51.1 to 243.0.51.62243.0.51.6362
78243.0.51.64/26243.0.51.65 to 243.0.51.126243.0.51.12762
79243.0.51.128/26243.0.51.129 to 243.0.51.190243.0.51.19162
80243.0.51.192/26243.0.51.193 to 243.0.51.254243.0.51.25562
81243.0.52.0/26243.0.52.1 to 243.0.52.62243.0.52.6362
82243.0.52.64/26243.0.52.65 to 243.0.52.126243.0.52.12762
83243.0.52.128/26243.0.52.129 to 243.0.52.190243.0.52.19162
84243.0.52.192/26243.0.52.193 to 243.0.52.254243.0.52.25562
85243.0.53.0/26243.0.53.1 to 243.0.53.62243.0.53.6362
86243.0.53.64/26243.0.53.65 to 243.0.53.126243.0.53.12762
87243.0.53.128/26243.0.53.129 to 243.0.53.190243.0.53.19162
88243.0.53.192/26243.0.53.193 to 243.0.53.254243.0.53.25562
89243.0.54.0/26243.0.54.1 to 243.0.54.62243.0.54.6362
90243.0.54.64/26243.0.54.65 to 243.0.54.126243.0.54.12762
91243.0.54.128/26243.0.54.129 to 243.0.54.190243.0.54.19162
92243.0.54.192/26243.0.54.193 to 243.0.54.254243.0.54.25562
93243.0.55.0/26243.0.55.1 to 243.0.55.62243.0.55.6362
94243.0.55.64/26243.0.55.65 to 243.0.55.126243.0.55.12762
95243.0.55.128/26243.0.55.129 to 243.0.55.190243.0.55.19162
96243.0.55.192/26243.0.55.193 to 243.0.55.254243.0.55.25562
97243.0.56.0/26243.0.56.1 to 243.0.56.62243.0.56.6362
98243.0.56.64/26243.0.56.65 to 243.0.56.126243.0.56.12762
99243.0.56.128/26243.0.56.129 to 243.0.56.190243.0.56.19162
100243.0.56.192/26243.0.56.193 to 243.0.56.254243.0.56.25562
101243.0.57.0/26243.0.57.1 to 243.0.57.62243.0.57.6362
102243.0.57.64/26243.0.57.65 to 243.0.57.126243.0.57.12762
103243.0.57.128/26243.0.57.129 to 243.0.57.190243.0.57.19162
104243.0.57.192/26243.0.57.193 to 243.0.57.254243.0.57.25562
105243.0.58.0/26243.0.58.1 to 243.0.58.62243.0.58.6362
106243.0.58.64/26243.0.58.65 to 243.0.58.126243.0.58.12762
107243.0.58.128/26243.0.58.129 to 243.0.58.190243.0.58.19162
108243.0.58.192/26243.0.58.193 to 243.0.58.254243.0.58.25562
109243.0.59.0/26243.0.59.1 to 243.0.59.62243.0.59.6362
110243.0.59.64/26243.0.59.65 to 243.0.59.126243.0.59.12762
111243.0.59.128/26243.0.59.129 to 243.0.59.190243.0.59.19162
112243.0.59.192/26243.0.59.193 to 243.0.59.254243.0.59.25562
113243.0.60.0/26243.0.60.1 to 243.0.60.62243.0.60.6362
114243.0.60.64/26243.0.60.65 to 243.0.60.126243.0.60.12762
115243.0.60.128/26243.0.60.129 to 243.0.60.190243.0.60.19162
116243.0.60.192/26243.0.60.193 to 243.0.60.254243.0.60.25562
117243.0.61.0/26243.0.61.1 to 243.0.61.62243.0.61.6362
118243.0.61.64/26243.0.61.65 to 243.0.61.126243.0.61.12762
119243.0.61.128/26243.0.61.129 to 243.0.61.190243.0.61.19162
120243.0.61.192/26243.0.61.193 to 243.0.61.254243.0.61.25562
121243.0.62.0/26243.0.62.1 to 243.0.62.62243.0.62.6362
122243.0.62.64/26243.0.62.65 to 243.0.62.126243.0.62.12762
123243.0.62.128/26243.0.62.129 to 243.0.62.190243.0.62.19162
124243.0.62.192/26243.0.62.193 to 243.0.62.254243.0.62.25562
125243.0.63.0/26243.0.63.1 to 243.0.63.62243.0.63.6362
126243.0.63.64/26243.0.63.65 to 243.0.63.126243.0.63.12762
127243.0.63.128/26243.0.63.129 to 243.0.63.190243.0.63.19162
128243.0.63.192/26243.0.63.193 to 243.0.63.254243.0.63.25562

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.