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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.

Network8.128.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
8.128.0.0
Broadcast address
8.191.255.255
First usable
8.128.0.1
Last usable
8.191.255.254
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 08800000 · Integer 142606336 to 146800639
Reverse DNS zones
128.8.in-addr.arpa
129.8.in-addr.arpa
130.8.in-addr.arpa
131.8.in-addr.arpa
132.8.in-addr.arpa
133.8.in-addr.arpa
134.8.in-addr.arpa
135.8.in-addr.arpa
136.8.in-addr.arpa
137.8.in-addr.arpa
138.8.in-addr.arpa
139.8.in-addr.arpa
140.8.in-addr.arpa
141.8.in-addr.arpa
142.8.in-addr.arpa
143.8.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
Address00001000.10000000.00000000.000000008.128.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network00001000.10000000.00000000.000000008.128.0.0
Broadcast00001000.10111111.11111111.111111118.191.255.255
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)

8.128.0.0/10 makes 128 subnets of /17.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
18.128.0.0/178.128.0.1 to 8.128.127.2548.128.127.25532,766
28.128.128.0/178.128.128.1 to 8.128.255.2548.128.255.25532,766
38.129.0.0/178.129.0.1 to 8.129.127.2548.129.127.25532,766
48.129.128.0/178.129.128.1 to 8.129.255.2548.129.255.25532,766
58.130.0.0/178.130.0.1 to 8.130.127.2548.130.127.25532,766
68.130.128.0/178.130.128.1 to 8.130.255.2548.130.255.25532,766
78.131.0.0/178.131.0.1 to 8.131.127.2548.131.127.25532,766
88.131.128.0/178.131.128.1 to 8.131.255.2548.131.255.25532,766
98.132.0.0/178.132.0.1 to 8.132.127.2548.132.127.25532,766
108.132.128.0/178.132.128.1 to 8.132.255.2548.132.255.25532,766
118.133.0.0/178.133.0.1 to 8.133.127.2548.133.127.25532,766
128.133.128.0/178.133.128.1 to 8.133.255.2548.133.255.25532,766
138.134.0.0/178.134.0.1 to 8.134.127.2548.134.127.25532,766
148.134.128.0/178.134.128.1 to 8.134.255.2548.134.255.25532,766
158.135.0.0/178.135.0.1 to 8.135.127.2548.135.127.25532,766
168.135.128.0/178.135.128.1 to 8.135.255.2548.135.255.25532,766
178.136.0.0/178.136.0.1 to 8.136.127.2548.136.127.25532,766
188.136.128.0/178.136.128.1 to 8.136.255.2548.136.255.25532,766
198.137.0.0/178.137.0.1 to 8.137.127.2548.137.127.25532,766
208.137.128.0/178.137.128.1 to 8.137.255.2548.137.255.25532,766
218.138.0.0/178.138.0.1 to 8.138.127.2548.138.127.25532,766
228.138.128.0/178.138.128.1 to 8.138.255.2548.138.255.25532,766
238.139.0.0/178.139.0.1 to 8.139.127.2548.139.127.25532,766
248.139.128.0/178.139.128.1 to 8.139.255.2548.139.255.25532,766
258.140.0.0/178.140.0.1 to 8.140.127.2548.140.127.25532,766
268.140.128.0/178.140.128.1 to 8.140.255.2548.140.255.25532,766
278.141.0.0/178.141.0.1 to 8.141.127.2548.141.127.25532,766
288.141.128.0/178.141.128.1 to 8.141.255.2548.141.255.25532,766
298.142.0.0/178.142.0.1 to 8.142.127.2548.142.127.25532,766
308.142.128.0/178.142.128.1 to 8.142.255.2548.142.255.25532,766
318.143.0.0/178.143.0.1 to 8.143.127.2548.143.127.25532,766
328.143.128.0/178.143.128.1 to 8.143.255.2548.143.255.25532,766
338.144.0.0/178.144.0.1 to 8.144.127.2548.144.127.25532,766
348.144.128.0/178.144.128.1 to 8.144.255.2548.144.255.25532,766
358.145.0.0/178.145.0.1 to 8.145.127.2548.145.127.25532,766
368.145.128.0/178.145.128.1 to 8.145.255.2548.145.255.25532,766
378.146.0.0/178.146.0.1 to 8.146.127.2548.146.127.25532,766
388.146.128.0/178.146.128.1 to 8.146.255.2548.146.255.25532,766
398.147.0.0/178.147.0.1 to 8.147.127.2548.147.127.25532,766
408.147.128.0/178.147.128.1 to 8.147.255.2548.147.255.25532,766
418.148.0.0/178.148.0.1 to 8.148.127.2548.148.127.25532,766
428.148.128.0/178.148.128.1 to 8.148.255.2548.148.255.25532,766
438.149.0.0/178.149.0.1 to 8.149.127.2548.149.127.25532,766
448.149.128.0/178.149.128.1 to 8.149.255.2548.149.255.25532,766
458.150.0.0/178.150.0.1 to 8.150.127.2548.150.127.25532,766
468.150.128.0/178.150.128.1 to 8.150.255.2548.150.255.25532,766
478.151.0.0/178.151.0.1 to 8.151.127.2548.151.127.25532,766
488.151.128.0/178.151.128.1 to 8.151.255.2548.151.255.25532,766
498.152.0.0/178.152.0.1 to 8.152.127.2548.152.127.25532,766
508.152.128.0/178.152.128.1 to 8.152.255.2548.152.255.25532,766
518.153.0.0/178.153.0.1 to 8.153.127.2548.153.127.25532,766
528.153.128.0/178.153.128.1 to 8.153.255.2548.153.255.25532,766
538.154.0.0/178.154.0.1 to 8.154.127.2548.154.127.25532,766
548.154.128.0/178.154.128.1 to 8.154.255.2548.154.255.25532,766
558.155.0.0/178.155.0.1 to 8.155.127.2548.155.127.25532,766
568.155.128.0/178.155.128.1 to 8.155.255.2548.155.255.25532,766
578.156.0.0/178.156.0.1 to 8.156.127.2548.156.127.25532,766
588.156.128.0/178.156.128.1 to 8.156.255.2548.156.255.25532,766
598.157.0.0/178.157.0.1 to 8.157.127.2548.157.127.25532,766
608.157.128.0/178.157.128.1 to 8.157.255.2548.157.255.25532,766
618.158.0.0/178.158.0.1 to 8.158.127.2548.158.127.25532,766
628.158.128.0/178.158.128.1 to 8.158.255.2548.158.255.25532,766
638.159.0.0/178.159.0.1 to 8.159.127.2548.159.127.25532,766
648.159.128.0/178.159.128.1 to 8.159.255.2548.159.255.25532,766
658.160.0.0/178.160.0.1 to 8.160.127.2548.160.127.25532,766
668.160.128.0/178.160.128.1 to 8.160.255.2548.160.255.25532,766
678.161.0.0/178.161.0.1 to 8.161.127.2548.161.127.25532,766
688.161.128.0/178.161.128.1 to 8.161.255.2548.161.255.25532,766
698.162.0.0/178.162.0.1 to 8.162.127.2548.162.127.25532,766
708.162.128.0/178.162.128.1 to 8.162.255.2548.162.255.25532,766
718.163.0.0/178.163.0.1 to 8.163.127.2548.163.127.25532,766
728.163.128.0/178.163.128.1 to 8.163.255.2548.163.255.25532,766
738.164.0.0/178.164.0.1 to 8.164.127.2548.164.127.25532,766
748.164.128.0/178.164.128.1 to 8.164.255.2548.164.255.25532,766
758.165.0.0/178.165.0.1 to 8.165.127.2548.165.127.25532,766
768.165.128.0/178.165.128.1 to 8.165.255.2548.165.255.25532,766
778.166.0.0/178.166.0.1 to 8.166.127.2548.166.127.25532,766
788.166.128.0/178.166.128.1 to 8.166.255.2548.166.255.25532,766
798.167.0.0/178.167.0.1 to 8.167.127.2548.167.127.25532,766
808.167.128.0/178.167.128.1 to 8.167.255.2548.167.255.25532,766
818.168.0.0/178.168.0.1 to 8.168.127.2548.168.127.25532,766
828.168.128.0/178.168.128.1 to 8.168.255.2548.168.255.25532,766
838.169.0.0/178.169.0.1 to 8.169.127.2548.169.127.25532,766
848.169.128.0/178.169.128.1 to 8.169.255.2548.169.255.25532,766
858.170.0.0/178.170.0.1 to 8.170.127.2548.170.127.25532,766
868.170.128.0/178.170.128.1 to 8.170.255.2548.170.255.25532,766
878.171.0.0/178.171.0.1 to 8.171.127.2548.171.127.25532,766
888.171.128.0/178.171.128.1 to 8.171.255.2548.171.255.25532,766
898.172.0.0/178.172.0.1 to 8.172.127.2548.172.127.25532,766
908.172.128.0/178.172.128.1 to 8.172.255.2548.172.255.25532,766
918.173.0.0/178.173.0.1 to 8.173.127.2548.173.127.25532,766
928.173.128.0/178.173.128.1 to 8.173.255.2548.173.255.25532,766
938.174.0.0/178.174.0.1 to 8.174.127.2548.174.127.25532,766
948.174.128.0/178.174.128.1 to 8.174.255.2548.174.255.25532,766
958.175.0.0/178.175.0.1 to 8.175.127.2548.175.127.25532,766
968.175.128.0/178.175.128.1 to 8.175.255.2548.175.255.25532,766
978.176.0.0/178.176.0.1 to 8.176.127.2548.176.127.25532,766
988.176.128.0/178.176.128.1 to 8.176.255.2548.176.255.25532,766
998.177.0.0/178.177.0.1 to 8.177.127.2548.177.127.25532,766
1008.177.128.0/178.177.128.1 to 8.177.255.2548.177.255.25532,766
1018.178.0.0/178.178.0.1 to 8.178.127.2548.178.127.25532,766
1028.178.128.0/178.178.128.1 to 8.178.255.2548.178.255.25532,766
1038.179.0.0/178.179.0.1 to 8.179.127.2548.179.127.25532,766
1048.179.128.0/178.179.128.1 to 8.179.255.2548.179.255.25532,766
1058.180.0.0/178.180.0.1 to 8.180.127.2548.180.127.25532,766
1068.180.128.0/178.180.128.1 to 8.180.255.2548.180.255.25532,766
1078.181.0.0/178.181.0.1 to 8.181.127.2548.181.127.25532,766
1088.181.128.0/178.181.128.1 to 8.181.255.2548.181.255.25532,766
1098.182.0.0/178.182.0.1 to 8.182.127.2548.182.127.25532,766
1108.182.128.0/178.182.128.1 to 8.182.255.2548.182.255.25532,766
1118.183.0.0/178.183.0.1 to 8.183.127.2548.183.127.25532,766
1128.183.128.0/178.183.128.1 to 8.183.255.2548.183.255.25532,766
1138.184.0.0/178.184.0.1 to 8.184.127.2548.184.127.25532,766
1148.184.128.0/178.184.128.1 to 8.184.255.2548.184.255.25532,766
1158.185.0.0/178.185.0.1 to 8.185.127.2548.185.127.25532,766
1168.185.128.0/178.185.128.1 to 8.185.255.2548.185.255.25532,766
1178.186.0.0/178.186.0.1 to 8.186.127.2548.186.127.25532,766
1188.186.128.0/178.186.128.1 to 8.186.255.2548.186.255.25532,766
1198.187.0.0/178.187.0.1 to 8.187.127.2548.187.127.25532,766
1208.187.128.0/178.187.128.1 to 8.187.255.2548.187.255.25532,766
1218.188.0.0/178.188.0.1 to 8.188.127.2548.188.127.25532,766
1228.188.128.0/178.188.128.1 to 8.188.255.2548.188.255.25532,766
1238.189.0.0/178.189.0.1 to 8.189.127.2548.189.127.25532,766
1248.189.128.0/178.189.128.1 to 8.189.255.2548.189.255.25532,766
1258.190.0.0/178.190.0.1 to 8.190.127.2548.190.127.25532,766
1268.190.128.0/178.190.128.1 to 8.190.255.2548.190.255.25532,766
1278.191.0.0/178.191.0.1 to 8.191.127.2548.191.127.25532,766
1288.191.128.0/178.191.128.1 to 8.191.255.2548.191.255.25532,766

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.