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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.

Network99.0.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
99.0.0.0
Broadcast address
99.1.255.255
First usable
99.0.0.1
Last usable
99.1.255.254
Usable hosts
131,070 (131,072 less the network and broadcast addresses)
Subnet mask
255.254.0.0
Wildcard mask
0.1.255.255 (Cisco ACLs, OSPF)
Prefix length
/15
Type
Public public
Old class
A (default /8)
As numbers
Hex 63000000 · Integer 1660944384 to 1661075455
Reverse DNS zones
0.99.in-addr.arpa
1.99.in-addr.arpa
/15 is not on a 8-bit boundary, so it takes 2 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01100011.00000000.00000000.0000000099.0.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network01100011.00000000.00000000.0000000099.0.0.0
Broadcast01100011.00000001.11111111.1111111199.1.255.255
Split into smaller subnets/22
/16 (2)/17 (4)/18 (8)/19 (16)/20 (32)/21 (64)/22 (128)/23 (256)/24 (512)/25 (1,024)/26 (2,048)/27 (4,096)

99.0.0.0/15 makes 128 subnets of /22.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
199.0.0.0/2299.0.0.1 to 99.0.3.25499.0.3.2551,022
299.0.4.0/2299.0.4.1 to 99.0.7.25499.0.7.2551,022
399.0.8.0/2299.0.8.1 to 99.0.11.25499.0.11.2551,022
499.0.12.0/2299.0.12.1 to 99.0.15.25499.0.15.2551,022
599.0.16.0/2299.0.16.1 to 99.0.19.25499.0.19.2551,022
699.0.20.0/2299.0.20.1 to 99.0.23.25499.0.23.2551,022
799.0.24.0/2299.0.24.1 to 99.0.27.25499.0.27.2551,022
899.0.28.0/2299.0.28.1 to 99.0.31.25499.0.31.2551,022
999.0.32.0/2299.0.32.1 to 99.0.35.25499.0.35.2551,022
1099.0.36.0/2299.0.36.1 to 99.0.39.25499.0.39.2551,022
1199.0.40.0/2299.0.40.1 to 99.0.43.25499.0.43.2551,022
1299.0.44.0/2299.0.44.1 to 99.0.47.25499.0.47.2551,022
1399.0.48.0/2299.0.48.1 to 99.0.51.25499.0.51.2551,022
1499.0.52.0/2299.0.52.1 to 99.0.55.25499.0.55.2551,022
1599.0.56.0/2299.0.56.1 to 99.0.59.25499.0.59.2551,022
1699.0.60.0/2299.0.60.1 to 99.0.63.25499.0.63.2551,022
1799.0.64.0/2299.0.64.1 to 99.0.67.25499.0.67.2551,022
1899.0.68.0/2299.0.68.1 to 99.0.71.25499.0.71.2551,022
1999.0.72.0/2299.0.72.1 to 99.0.75.25499.0.75.2551,022
2099.0.76.0/2299.0.76.1 to 99.0.79.25499.0.79.2551,022
2199.0.80.0/2299.0.80.1 to 99.0.83.25499.0.83.2551,022
2299.0.84.0/2299.0.84.1 to 99.0.87.25499.0.87.2551,022
2399.0.88.0/2299.0.88.1 to 99.0.91.25499.0.91.2551,022
2499.0.92.0/2299.0.92.1 to 99.0.95.25499.0.95.2551,022
2599.0.96.0/2299.0.96.1 to 99.0.99.25499.0.99.2551,022
2699.0.100.0/2299.0.100.1 to 99.0.103.25499.0.103.2551,022
2799.0.104.0/2299.0.104.1 to 99.0.107.25499.0.107.2551,022
2899.0.108.0/2299.0.108.1 to 99.0.111.25499.0.111.2551,022
2999.0.112.0/2299.0.112.1 to 99.0.115.25499.0.115.2551,022
3099.0.116.0/2299.0.116.1 to 99.0.119.25499.0.119.2551,022
3199.0.120.0/2299.0.120.1 to 99.0.123.25499.0.123.2551,022
3299.0.124.0/2299.0.124.1 to 99.0.127.25499.0.127.2551,022
3399.0.128.0/2299.0.128.1 to 99.0.131.25499.0.131.2551,022
3499.0.132.0/2299.0.132.1 to 99.0.135.25499.0.135.2551,022
3599.0.136.0/2299.0.136.1 to 99.0.139.25499.0.139.2551,022
3699.0.140.0/2299.0.140.1 to 99.0.143.25499.0.143.2551,022
3799.0.144.0/2299.0.144.1 to 99.0.147.25499.0.147.2551,022
3899.0.148.0/2299.0.148.1 to 99.0.151.25499.0.151.2551,022
3999.0.152.0/2299.0.152.1 to 99.0.155.25499.0.155.2551,022
4099.0.156.0/2299.0.156.1 to 99.0.159.25499.0.159.2551,022
4199.0.160.0/2299.0.160.1 to 99.0.163.25499.0.163.2551,022
4299.0.164.0/2299.0.164.1 to 99.0.167.25499.0.167.2551,022
4399.0.168.0/2299.0.168.1 to 99.0.171.25499.0.171.2551,022
4499.0.172.0/2299.0.172.1 to 99.0.175.25499.0.175.2551,022
4599.0.176.0/2299.0.176.1 to 99.0.179.25499.0.179.2551,022
4699.0.180.0/2299.0.180.1 to 99.0.183.25499.0.183.2551,022
4799.0.184.0/2299.0.184.1 to 99.0.187.25499.0.187.2551,022
4899.0.188.0/2299.0.188.1 to 99.0.191.25499.0.191.2551,022
4999.0.192.0/2299.0.192.1 to 99.0.195.25499.0.195.2551,022
5099.0.196.0/2299.0.196.1 to 99.0.199.25499.0.199.2551,022
5199.0.200.0/2299.0.200.1 to 99.0.203.25499.0.203.2551,022
5299.0.204.0/2299.0.204.1 to 99.0.207.25499.0.207.2551,022
5399.0.208.0/2299.0.208.1 to 99.0.211.25499.0.211.2551,022
5499.0.212.0/2299.0.212.1 to 99.0.215.25499.0.215.2551,022
5599.0.216.0/2299.0.216.1 to 99.0.219.25499.0.219.2551,022
5699.0.220.0/2299.0.220.1 to 99.0.223.25499.0.223.2551,022
5799.0.224.0/2299.0.224.1 to 99.0.227.25499.0.227.2551,022
5899.0.228.0/2299.0.228.1 to 99.0.231.25499.0.231.2551,022
5999.0.232.0/2299.0.232.1 to 99.0.235.25499.0.235.2551,022
6099.0.236.0/2299.0.236.1 to 99.0.239.25499.0.239.2551,022
6199.0.240.0/2299.0.240.1 to 99.0.243.25499.0.243.2551,022
6299.0.244.0/2299.0.244.1 to 99.0.247.25499.0.247.2551,022
6399.0.248.0/2299.0.248.1 to 99.0.251.25499.0.251.2551,022
6499.0.252.0/2299.0.252.1 to 99.0.255.25499.0.255.2551,022
6599.1.0.0/2299.1.0.1 to 99.1.3.25499.1.3.2551,022
6699.1.4.0/2299.1.4.1 to 99.1.7.25499.1.7.2551,022
6799.1.8.0/2299.1.8.1 to 99.1.11.25499.1.11.2551,022
6899.1.12.0/2299.1.12.1 to 99.1.15.25499.1.15.2551,022
6999.1.16.0/2299.1.16.1 to 99.1.19.25499.1.19.2551,022
7099.1.20.0/2299.1.20.1 to 99.1.23.25499.1.23.2551,022
7199.1.24.0/2299.1.24.1 to 99.1.27.25499.1.27.2551,022
7299.1.28.0/2299.1.28.1 to 99.1.31.25499.1.31.2551,022
7399.1.32.0/2299.1.32.1 to 99.1.35.25499.1.35.2551,022
7499.1.36.0/2299.1.36.1 to 99.1.39.25499.1.39.2551,022
7599.1.40.0/2299.1.40.1 to 99.1.43.25499.1.43.2551,022
7699.1.44.0/2299.1.44.1 to 99.1.47.25499.1.47.2551,022
7799.1.48.0/2299.1.48.1 to 99.1.51.25499.1.51.2551,022
7899.1.52.0/2299.1.52.1 to 99.1.55.25499.1.55.2551,022
7999.1.56.0/2299.1.56.1 to 99.1.59.25499.1.59.2551,022
8099.1.60.0/2299.1.60.1 to 99.1.63.25499.1.63.2551,022
8199.1.64.0/2299.1.64.1 to 99.1.67.25499.1.67.2551,022
8299.1.68.0/2299.1.68.1 to 99.1.71.25499.1.71.2551,022
8399.1.72.0/2299.1.72.1 to 99.1.75.25499.1.75.2551,022
8499.1.76.0/2299.1.76.1 to 99.1.79.25499.1.79.2551,022
8599.1.80.0/2299.1.80.1 to 99.1.83.25499.1.83.2551,022
8699.1.84.0/2299.1.84.1 to 99.1.87.25499.1.87.2551,022
8799.1.88.0/2299.1.88.1 to 99.1.91.25499.1.91.2551,022
8899.1.92.0/2299.1.92.1 to 99.1.95.25499.1.95.2551,022
8999.1.96.0/2299.1.96.1 to 99.1.99.25499.1.99.2551,022
9099.1.100.0/2299.1.100.1 to 99.1.103.25499.1.103.2551,022
9199.1.104.0/2299.1.104.1 to 99.1.107.25499.1.107.2551,022
9299.1.108.0/2299.1.108.1 to 99.1.111.25499.1.111.2551,022
9399.1.112.0/2299.1.112.1 to 99.1.115.25499.1.115.2551,022
9499.1.116.0/2299.1.116.1 to 99.1.119.25499.1.119.2551,022
9599.1.120.0/2299.1.120.1 to 99.1.123.25499.1.123.2551,022
9699.1.124.0/2299.1.124.1 to 99.1.127.25499.1.127.2551,022
9799.1.128.0/2299.1.128.1 to 99.1.131.25499.1.131.2551,022
9899.1.132.0/2299.1.132.1 to 99.1.135.25499.1.135.2551,022
9999.1.136.0/2299.1.136.1 to 99.1.139.25499.1.139.2551,022
10099.1.140.0/2299.1.140.1 to 99.1.143.25499.1.143.2551,022
10199.1.144.0/2299.1.144.1 to 99.1.147.25499.1.147.2551,022
10299.1.148.0/2299.1.148.1 to 99.1.151.25499.1.151.2551,022
10399.1.152.0/2299.1.152.1 to 99.1.155.25499.1.155.2551,022
10499.1.156.0/2299.1.156.1 to 99.1.159.25499.1.159.2551,022
10599.1.160.0/2299.1.160.1 to 99.1.163.25499.1.163.2551,022
10699.1.164.0/2299.1.164.1 to 99.1.167.25499.1.167.2551,022
10799.1.168.0/2299.1.168.1 to 99.1.171.25499.1.171.2551,022
10899.1.172.0/2299.1.172.1 to 99.1.175.25499.1.175.2551,022
10999.1.176.0/2299.1.176.1 to 99.1.179.25499.1.179.2551,022
11099.1.180.0/2299.1.180.1 to 99.1.183.25499.1.183.2551,022
11199.1.184.0/2299.1.184.1 to 99.1.187.25499.1.187.2551,022
11299.1.188.0/2299.1.188.1 to 99.1.191.25499.1.191.2551,022
11399.1.192.0/2299.1.192.1 to 99.1.195.25499.1.195.2551,022
11499.1.196.0/2299.1.196.1 to 99.1.199.25499.1.199.2551,022
11599.1.200.0/2299.1.200.1 to 99.1.203.25499.1.203.2551,022
11699.1.204.0/2299.1.204.1 to 99.1.207.25499.1.207.2551,022
11799.1.208.0/2299.1.208.1 to 99.1.211.25499.1.211.2551,022
11899.1.212.0/2299.1.212.1 to 99.1.215.25499.1.215.2551,022
11999.1.216.0/2299.1.216.1 to 99.1.219.25499.1.219.2551,022
12099.1.220.0/2299.1.220.1 to 99.1.223.25499.1.223.2551,022
12199.1.224.0/2299.1.224.1 to 99.1.227.25499.1.227.2551,022
12299.1.228.0/2299.1.228.1 to 99.1.231.25499.1.231.2551,022
12399.1.232.0/2299.1.232.1 to 99.1.235.25499.1.235.2551,022
12499.1.236.0/2299.1.236.1 to 99.1.239.25499.1.239.2551,022
12599.1.240.0/2299.1.240.1 to 99.1.243.25499.1.243.2551,022
12699.1.244.0/2299.1.244.1 to 99.1.247.25499.1.247.2551,022
12799.1.248.0/2299.1.248.1 to 99.1.251.25499.1.251.2551,022
12899.1.252.0/2299.1.252.1 to 99.1.255.25499.1.255.2551,022

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.