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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.

Network55.128.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
55.128.0.0
Broadcast address
55.191.255.255
First usable
55.128.0.1
Last usable
55.191.255.254
Usable hosts
4,194,302 (4,194,304 less the network and broadcast addresses)
Subnet mask
255.192.0.0
Wildcard mask
0.63.255.255 (Cisco ACLs, OSPF)
Prefix length
/10
Type
Public public
Old class
A (default /8)
As numbers
Hex 37800000 · Integer 931135488 to 935329791
Reverse DNS zones
128.55.in-addr.arpa
129.55.in-addr.arpa
130.55.in-addr.arpa
131.55.in-addr.arpa
132.55.in-addr.arpa
133.55.in-addr.arpa
134.55.in-addr.arpa
135.55.in-addr.arpa
136.55.in-addr.arpa
137.55.in-addr.arpa
138.55.in-addr.arpa
139.55.in-addr.arpa
140.55.in-addr.arpa
141.55.in-addr.arpa
142.55.in-addr.arpa
143.55.in-addr.arpa
and 48 more
/10 is not on a 8-bit boundary, so it takes 64 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00110111.10000000.00000000.0000000055.128.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network00110111.10000000.00000000.0000000055.128.0.0
Broadcast00110111.10111111.11111111.1111111155.191.255.255
Split into smaller subnets/17
/11 (2)/12 (4)/13 (8)/14 (16)/15 (32)/16 (64)/17 (128)/18 (256)/19 (512)/20 (1,024)/21 (2,048)/22 (4,096)

55.128.0.0/10 makes 128 subnets of /17.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
155.128.0.0/1755.128.0.1 to 55.128.127.25455.128.127.25532,766
255.128.128.0/1755.128.128.1 to 55.128.255.25455.128.255.25532,766
355.129.0.0/1755.129.0.1 to 55.129.127.25455.129.127.25532,766
455.129.128.0/1755.129.128.1 to 55.129.255.25455.129.255.25532,766
555.130.0.0/1755.130.0.1 to 55.130.127.25455.130.127.25532,766
655.130.128.0/1755.130.128.1 to 55.130.255.25455.130.255.25532,766
755.131.0.0/1755.131.0.1 to 55.131.127.25455.131.127.25532,766
855.131.128.0/1755.131.128.1 to 55.131.255.25455.131.255.25532,766
955.132.0.0/1755.132.0.1 to 55.132.127.25455.132.127.25532,766
1055.132.128.0/1755.132.128.1 to 55.132.255.25455.132.255.25532,766
1155.133.0.0/1755.133.0.1 to 55.133.127.25455.133.127.25532,766
1255.133.128.0/1755.133.128.1 to 55.133.255.25455.133.255.25532,766
1355.134.0.0/1755.134.0.1 to 55.134.127.25455.134.127.25532,766
1455.134.128.0/1755.134.128.1 to 55.134.255.25455.134.255.25532,766
1555.135.0.0/1755.135.0.1 to 55.135.127.25455.135.127.25532,766
1655.135.128.0/1755.135.128.1 to 55.135.255.25455.135.255.25532,766
1755.136.0.0/1755.136.0.1 to 55.136.127.25455.136.127.25532,766
1855.136.128.0/1755.136.128.1 to 55.136.255.25455.136.255.25532,766
1955.137.0.0/1755.137.0.1 to 55.137.127.25455.137.127.25532,766
2055.137.128.0/1755.137.128.1 to 55.137.255.25455.137.255.25532,766
2155.138.0.0/1755.138.0.1 to 55.138.127.25455.138.127.25532,766
2255.138.128.0/1755.138.128.1 to 55.138.255.25455.138.255.25532,766
2355.139.0.0/1755.139.0.1 to 55.139.127.25455.139.127.25532,766
2455.139.128.0/1755.139.128.1 to 55.139.255.25455.139.255.25532,766
2555.140.0.0/1755.140.0.1 to 55.140.127.25455.140.127.25532,766
2655.140.128.0/1755.140.128.1 to 55.140.255.25455.140.255.25532,766
2755.141.0.0/1755.141.0.1 to 55.141.127.25455.141.127.25532,766
2855.141.128.0/1755.141.128.1 to 55.141.255.25455.141.255.25532,766
2955.142.0.0/1755.142.0.1 to 55.142.127.25455.142.127.25532,766
3055.142.128.0/1755.142.128.1 to 55.142.255.25455.142.255.25532,766
3155.143.0.0/1755.143.0.1 to 55.143.127.25455.143.127.25532,766
3255.143.128.0/1755.143.128.1 to 55.143.255.25455.143.255.25532,766
3355.144.0.0/1755.144.0.1 to 55.144.127.25455.144.127.25532,766
3455.144.128.0/1755.144.128.1 to 55.144.255.25455.144.255.25532,766
3555.145.0.0/1755.145.0.1 to 55.145.127.25455.145.127.25532,766
3655.145.128.0/1755.145.128.1 to 55.145.255.25455.145.255.25532,766
3755.146.0.0/1755.146.0.1 to 55.146.127.25455.146.127.25532,766
3855.146.128.0/1755.146.128.1 to 55.146.255.25455.146.255.25532,766
3955.147.0.0/1755.147.0.1 to 55.147.127.25455.147.127.25532,766
4055.147.128.0/1755.147.128.1 to 55.147.255.25455.147.255.25532,766
4155.148.0.0/1755.148.0.1 to 55.148.127.25455.148.127.25532,766
4255.148.128.0/1755.148.128.1 to 55.148.255.25455.148.255.25532,766
4355.149.0.0/1755.149.0.1 to 55.149.127.25455.149.127.25532,766
4455.149.128.0/1755.149.128.1 to 55.149.255.25455.149.255.25532,766
4555.150.0.0/1755.150.0.1 to 55.150.127.25455.150.127.25532,766
4655.150.128.0/1755.150.128.1 to 55.150.255.25455.150.255.25532,766
4755.151.0.0/1755.151.0.1 to 55.151.127.25455.151.127.25532,766
4855.151.128.0/1755.151.128.1 to 55.151.255.25455.151.255.25532,766
4955.152.0.0/1755.152.0.1 to 55.152.127.25455.152.127.25532,766
5055.152.128.0/1755.152.128.1 to 55.152.255.25455.152.255.25532,766
5155.153.0.0/1755.153.0.1 to 55.153.127.25455.153.127.25532,766
5255.153.128.0/1755.153.128.1 to 55.153.255.25455.153.255.25532,766
5355.154.0.0/1755.154.0.1 to 55.154.127.25455.154.127.25532,766
5455.154.128.0/1755.154.128.1 to 55.154.255.25455.154.255.25532,766
5555.155.0.0/1755.155.0.1 to 55.155.127.25455.155.127.25532,766
5655.155.128.0/1755.155.128.1 to 55.155.255.25455.155.255.25532,766
5755.156.0.0/1755.156.0.1 to 55.156.127.25455.156.127.25532,766
5855.156.128.0/1755.156.128.1 to 55.156.255.25455.156.255.25532,766
5955.157.0.0/1755.157.0.1 to 55.157.127.25455.157.127.25532,766
6055.157.128.0/1755.157.128.1 to 55.157.255.25455.157.255.25532,766
6155.158.0.0/1755.158.0.1 to 55.158.127.25455.158.127.25532,766
6255.158.128.0/1755.158.128.1 to 55.158.255.25455.158.255.25532,766
6355.159.0.0/1755.159.0.1 to 55.159.127.25455.159.127.25532,766
6455.159.128.0/1755.159.128.1 to 55.159.255.25455.159.255.25532,766
6555.160.0.0/1755.160.0.1 to 55.160.127.25455.160.127.25532,766
6655.160.128.0/1755.160.128.1 to 55.160.255.25455.160.255.25532,766
6755.161.0.0/1755.161.0.1 to 55.161.127.25455.161.127.25532,766
6855.161.128.0/1755.161.128.1 to 55.161.255.25455.161.255.25532,766
6955.162.0.0/1755.162.0.1 to 55.162.127.25455.162.127.25532,766
7055.162.128.0/1755.162.128.1 to 55.162.255.25455.162.255.25532,766
7155.163.0.0/1755.163.0.1 to 55.163.127.25455.163.127.25532,766
7255.163.128.0/1755.163.128.1 to 55.163.255.25455.163.255.25532,766
7355.164.0.0/1755.164.0.1 to 55.164.127.25455.164.127.25532,766
7455.164.128.0/1755.164.128.1 to 55.164.255.25455.164.255.25532,766
7555.165.0.0/1755.165.0.1 to 55.165.127.25455.165.127.25532,766
7655.165.128.0/1755.165.128.1 to 55.165.255.25455.165.255.25532,766
7755.166.0.0/1755.166.0.1 to 55.166.127.25455.166.127.25532,766
7855.166.128.0/1755.166.128.1 to 55.166.255.25455.166.255.25532,766
7955.167.0.0/1755.167.0.1 to 55.167.127.25455.167.127.25532,766
8055.167.128.0/1755.167.128.1 to 55.167.255.25455.167.255.25532,766
8155.168.0.0/1755.168.0.1 to 55.168.127.25455.168.127.25532,766
8255.168.128.0/1755.168.128.1 to 55.168.255.25455.168.255.25532,766
8355.169.0.0/1755.169.0.1 to 55.169.127.25455.169.127.25532,766
8455.169.128.0/1755.169.128.1 to 55.169.255.25455.169.255.25532,766
8555.170.0.0/1755.170.0.1 to 55.170.127.25455.170.127.25532,766
8655.170.128.0/1755.170.128.1 to 55.170.255.25455.170.255.25532,766
8755.171.0.0/1755.171.0.1 to 55.171.127.25455.171.127.25532,766
8855.171.128.0/1755.171.128.1 to 55.171.255.25455.171.255.25532,766
8955.172.0.0/1755.172.0.1 to 55.172.127.25455.172.127.25532,766
9055.172.128.0/1755.172.128.1 to 55.172.255.25455.172.255.25532,766
9155.173.0.0/1755.173.0.1 to 55.173.127.25455.173.127.25532,766
9255.173.128.0/1755.173.128.1 to 55.173.255.25455.173.255.25532,766
9355.174.0.0/1755.174.0.1 to 55.174.127.25455.174.127.25532,766
9455.174.128.0/1755.174.128.1 to 55.174.255.25455.174.255.25532,766
9555.175.0.0/1755.175.0.1 to 55.175.127.25455.175.127.25532,766
9655.175.128.0/1755.175.128.1 to 55.175.255.25455.175.255.25532,766
9755.176.0.0/1755.176.0.1 to 55.176.127.25455.176.127.25532,766
9855.176.128.0/1755.176.128.1 to 55.176.255.25455.176.255.25532,766
9955.177.0.0/1755.177.0.1 to 55.177.127.25455.177.127.25532,766
10055.177.128.0/1755.177.128.1 to 55.177.255.25455.177.255.25532,766
10155.178.0.0/1755.178.0.1 to 55.178.127.25455.178.127.25532,766
10255.178.128.0/1755.178.128.1 to 55.178.255.25455.178.255.25532,766
10355.179.0.0/1755.179.0.1 to 55.179.127.25455.179.127.25532,766
10455.179.128.0/1755.179.128.1 to 55.179.255.25455.179.255.25532,766
10555.180.0.0/1755.180.0.1 to 55.180.127.25455.180.127.25532,766
10655.180.128.0/1755.180.128.1 to 55.180.255.25455.180.255.25532,766
10755.181.0.0/1755.181.0.1 to 55.181.127.25455.181.127.25532,766
10855.181.128.0/1755.181.128.1 to 55.181.255.25455.181.255.25532,766
10955.182.0.0/1755.182.0.1 to 55.182.127.25455.182.127.25532,766
11055.182.128.0/1755.182.128.1 to 55.182.255.25455.182.255.25532,766
11155.183.0.0/1755.183.0.1 to 55.183.127.25455.183.127.25532,766
11255.183.128.0/1755.183.128.1 to 55.183.255.25455.183.255.25532,766
11355.184.0.0/1755.184.0.1 to 55.184.127.25455.184.127.25532,766
11455.184.128.0/1755.184.128.1 to 55.184.255.25455.184.255.25532,766
11555.185.0.0/1755.185.0.1 to 55.185.127.25455.185.127.25532,766
11655.185.128.0/1755.185.128.1 to 55.185.255.25455.185.255.25532,766
11755.186.0.0/1755.186.0.1 to 55.186.127.25455.186.127.25532,766
11855.186.128.0/1755.186.128.1 to 55.186.255.25455.186.255.25532,766
11955.187.0.0/1755.187.0.1 to 55.187.127.25455.187.127.25532,766
12055.187.128.0/1755.187.128.1 to 55.187.255.25455.187.255.25532,766
12155.188.0.0/1755.188.0.1 to 55.188.127.25455.188.127.25532,766
12255.188.128.0/1755.188.128.1 to 55.188.255.25455.188.255.25532,766
12355.189.0.0/1755.189.0.1 to 55.189.127.25455.189.127.25532,766
12455.189.128.0/1755.189.128.1 to 55.189.255.25455.189.255.25532,766
12555.190.0.0/1755.190.0.1 to 55.190.127.25455.190.127.25532,766
12655.190.128.0/1755.190.128.1 to 55.190.255.25455.190.255.25532,766
12755.191.0.0/1755.191.0.1 to 55.191.127.25455.191.127.25532,766
12855.191.128.0/1755.191.128.1 to 55.191.255.25455.191.255.25532,766

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.