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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.

Network33.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
33.0.0.0
Broadcast address
33.127.255.255
First usable
33.0.0.1
Last usable
33.127.255.254
Usable hosts
8,388,606 (8,388,608 less the network and broadcast addresses)
Subnet mask
255.128.0.0
Wildcard mask
0.127.255.255 (Cisco ACLs, OSPF)
Prefix length
/9
Type
Public public
Old class
A (default /8)
As numbers
Hex 21000000 · Integer 553648128 to 562036735
Reverse DNS zones
0.33.in-addr.arpa
1.33.in-addr.arpa
2.33.in-addr.arpa
3.33.in-addr.arpa
4.33.in-addr.arpa
5.33.in-addr.arpa
6.33.in-addr.arpa
7.33.in-addr.arpa
8.33.in-addr.arpa
9.33.in-addr.arpa
10.33.in-addr.arpa
11.33.in-addr.arpa
12.33.in-addr.arpa
13.33.in-addr.arpa
14.33.in-addr.arpa
15.33.in-addr.arpa
and 112 more
/9 is not on a 8-bit boundary, so it takes 128 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00100001.00000000.00000000.0000000033.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network00100001.00000000.00000000.0000000033.0.0.0
Broadcast00100001.01111111.11111111.1111111133.127.255.255
Split into smaller subnets/16
/10 (2)/11 (4)/12 (8)/13 (16)/14 (32)/15 (64)/16 (128)/17 (256)/18 (512)/19 (1,024)/20 (2,048)/21 (4,096)

33.0.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
133.0.0.0/1633.0.0.1 to 33.0.255.25433.0.255.25565,534
233.1.0.0/1633.1.0.1 to 33.1.255.25433.1.255.25565,534
333.2.0.0/1633.2.0.1 to 33.2.255.25433.2.255.25565,534
433.3.0.0/1633.3.0.1 to 33.3.255.25433.3.255.25565,534
533.4.0.0/1633.4.0.1 to 33.4.255.25433.4.255.25565,534
633.5.0.0/1633.5.0.1 to 33.5.255.25433.5.255.25565,534
733.6.0.0/1633.6.0.1 to 33.6.255.25433.6.255.25565,534
833.7.0.0/1633.7.0.1 to 33.7.255.25433.7.255.25565,534
933.8.0.0/1633.8.0.1 to 33.8.255.25433.8.255.25565,534
1033.9.0.0/1633.9.0.1 to 33.9.255.25433.9.255.25565,534
1133.10.0.0/1633.10.0.1 to 33.10.255.25433.10.255.25565,534
1233.11.0.0/1633.11.0.1 to 33.11.255.25433.11.255.25565,534
1333.12.0.0/1633.12.0.1 to 33.12.255.25433.12.255.25565,534
1433.13.0.0/1633.13.0.1 to 33.13.255.25433.13.255.25565,534
1533.14.0.0/1633.14.0.1 to 33.14.255.25433.14.255.25565,534
1633.15.0.0/1633.15.0.1 to 33.15.255.25433.15.255.25565,534
1733.16.0.0/1633.16.0.1 to 33.16.255.25433.16.255.25565,534
1833.17.0.0/1633.17.0.1 to 33.17.255.25433.17.255.25565,534
1933.18.0.0/1633.18.0.1 to 33.18.255.25433.18.255.25565,534
2033.19.0.0/1633.19.0.1 to 33.19.255.25433.19.255.25565,534
2133.20.0.0/1633.20.0.1 to 33.20.255.25433.20.255.25565,534
2233.21.0.0/1633.21.0.1 to 33.21.255.25433.21.255.25565,534
2333.22.0.0/1633.22.0.1 to 33.22.255.25433.22.255.25565,534
2433.23.0.0/1633.23.0.1 to 33.23.255.25433.23.255.25565,534
2533.24.0.0/1633.24.0.1 to 33.24.255.25433.24.255.25565,534
2633.25.0.0/1633.25.0.1 to 33.25.255.25433.25.255.25565,534
2733.26.0.0/1633.26.0.1 to 33.26.255.25433.26.255.25565,534
2833.27.0.0/1633.27.0.1 to 33.27.255.25433.27.255.25565,534
2933.28.0.0/1633.28.0.1 to 33.28.255.25433.28.255.25565,534
3033.29.0.0/1633.29.0.1 to 33.29.255.25433.29.255.25565,534
3133.30.0.0/1633.30.0.1 to 33.30.255.25433.30.255.25565,534
3233.31.0.0/1633.31.0.1 to 33.31.255.25433.31.255.25565,534
3333.32.0.0/1633.32.0.1 to 33.32.255.25433.32.255.25565,534
3433.33.0.0/1633.33.0.1 to 33.33.255.25433.33.255.25565,534
3533.34.0.0/1633.34.0.1 to 33.34.255.25433.34.255.25565,534
3633.35.0.0/1633.35.0.1 to 33.35.255.25433.35.255.25565,534
3733.36.0.0/1633.36.0.1 to 33.36.255.25433.36.255.25565,534
3833.37.0.0/1633.37.0.1 to 33.37.255.25433.37.255.25565,534
3933.38.0.0/1633.38.0.1 to 33.38.255.25433.38.255.25565,534
4033.39.0.0/1633.39.0.1 to 33.39.255.25433.39.255.25565,534
4133.40.0.0/1633.40.0.1 to 33.40.255.25433.40.255.25565,534
4233.41.0.0/1633.41.0.1 to 33.41.255.25433.41.255.25565,534
4333.42.0.0/1633.42.0.1 to 33.42.255.25433.42.255.25565,534
4433.43.0.0/1633.43.0.1 to 33.43.255.25433.43.255.25565,534
4533.44.0.0/1633.44.0.1 to 33.44.255.25433.44.255.25565,534
4633.45.0.0/1633.45.0.1 to 33.45.255.25433.45.255.25565,534
4733.46.0.0/1633.46.0.1 to 33.46.255.25433.46.255.25565,534
4833.47.0.0/1633.47.0.1 to 33.47.255.25433.47.255.25565,534
4933.48.0.0/1633.48.0.1 to 33.48.255.25433.48.255.25565,534
5033.49.0.0/1633.49.0.1 to 33.49.255.25433.49.255.25565,534
5133.50.0.0/1633.50.0.1 to 33.50.255.25433.50.255.25565,534
5233.51.0.0/1633.51.0.1 to 33.51.255.25433.51.255.25565,534
5333.52.0.0/1633.52.0.1 to 33.52.255.25433.52.255.25565,534
5433.53.0.0/1633.53.0.1 to 33.53.255.25433.53.255.25565,534
5533.54.0.0/1633.54.0.1 to 33.54.255.25433.54.255.25565,534
5633.55.0.0/1633.55.0.1 to 33.55.255.25433.55.255.25565,534
5733.56.0.0/1633.56.0.1 to 33.56.255.25433.56.255.25565,534
5833.57.0.0/1633.57.0.1 to 33.57.255.25433.57.255.25565,534
5933.58.0.0/1633.58.0.1 to 33.58.255.25433.58.255.25565,534
6033.59.0.0/1633.59.0.1 to 33.59.255.25433.59.255.25565,534
6133.60.0.0/1633.60.0.1 to 33.60.255.25433.60.255.25565,534
6233.61.0.0/1633.61.0.1 to 33.61.255.25433.61.255.25565,534
6333.62.0.0/1633.62.0.1 to 33.62.255.25433.62.255.25565,534
6433.63.0.0/1633.63.0.1 to 33.63.255.25433.63.255.25565,534
6533.64.0.0/1633.64.0.1 to 33.64.255.25433.64.255.25565,534
6633.65.0.0/1633.65.0.1 to 33.65.255.25433.65.255.25565,534
6733.66.0.0/1633.66.0.1 to 33.66.255.25433.66.255.25565,534
6833.67.0.0/1633.67.0.1 to 33.67.255.25433.67.255.25565,534
6933.68.0.0/1633.68.0.1 to 33.68.255.25433.68.255.25565,534
7033.69.0.0/1633.69.0.1 to 33.69.255.25433.69.255.25565,534
7133.70.0.0/1633.70.0.1 to 33.70.255.25433.70.255.25565,534
7233.71.0.0/1633.71.0.1 to 33.71.255.25433.71.255.25565,534
7333.72.0.0/1633.72.0.1 to 33.72.255.25433.72.255.25565,534
7433.73.0.0/1633.73.0.1 to 33.73.255.25433.73.255.25565,534
7533.74.0.0/1633.74.0.1 to 33.74.255.25433.74.255.25565,534
7633.75.0.0/1633.75.0.1 to 33.75.255.25433.75.255.25565,534
7733.76.0.0/1633.76.0.1 to 33.76.255.25433.76.255.25565,534
7833.77.0.0/1633.77.0.1 to 33.77.255.25433.77.255.25565,534
7933.78.0.0/1633.78.0.1 to 33.78.255.25433.78.255.25565,534
8033.79.0.0/1633.79.0.1 to 33.79.255.25433.79.255.25565,534
8133.80.0.0/1633.80.0.1 to 33.80.255.25433.80.255.25565,534
8233.81.0.0/1633.81.0.1 to 33.81.255.25433.81.255.25565,534
8333.82.0.0/1633.82.0.1 to 33.82.255.25433.82.255.25565,534
8433.83.0.0/1633.83.0.1 to 33.83.255.25433.83.255.25565,534
8533.84.0.0/1633.84.0.1 to 33.84.255.25433.84.255.25565,534
8633.85.0.0/1633.85.0.1 to 33.85.255.25433.85.255.25565,534
8733.86.0.0/1633.86.0.1 to 33.86.255.25433.86.255.25565,534
8833.87.0.0/1633.87.0.1 to 33.87.255.25433.87.255.25565,534
8933.88.0.0/1633.88.0.1 to 33.88.255.25433.88.255.25565,534
9033.89.0.0/1633.89.0.1 to 33.89.255.25433.89.255.25565,534
9133.90.0.0/1633.90.0.1 to 33.90.255.25433.90.255.25565,534
9233.91.0.0/1633.91.0.1 to 33.91.255.25433.91.255.25565,534
9333.92.0.0/1633.92.0.1 to 33.92.255.25433.92.255.25565,534
9433.93.0.0/1633.93.0.1 to 33.93.255.25433.93.255.25565,534
9533.94.0.0/1633.94.0.1 to 33.94.255.25433.94.255.25565,534
9633.95.0.0/1633.95.0.1 to 33.95.255.25433.95.255.25565,534
9733.96.0.0/1633.96.0.1 to 33.96.255.25433.96.255.25565,534
9833.97.0.0/1633.97.0.1 to 33.97.255.25433.97.255.25565,534
9933.98.0.0/1633.98.0.1 to 33.98.255.25433.98.255.25565,534
10033.99.0.0/1633.99.0.1 to 33.99.255.25433.99.255.25565,534
10133.100.0.0/1633.100.0.1 to 33.100.255.25433.100.255.25565,534
10233.101.0.0/1633.101.0.1 to 33.101.255.25433.101.255.25565,534
10333.102.0.0/1633.102.0.1 to 33.102.255.25433.102.255.25565,534
10433.103.0.0/1633.103.0.1 to 33.103.255.25433.103.255.25565,534
10533.104.0.0/1633.104.0.1 to 33.104.255.25433.104.255.25565,534
10633.105.0.0/1633.105.0.1 to 33.105.255.25433.105.255.25565,534
10733.106.0.0/1633.106.0.1 to 33.106.255.25433.106.255.25565,534
10833.107.0.0/1633.107.0.1 to 33.107.255.25433.107.255.25565,534
10933.108.0.0/1633.108.0.1 to 33.108.255.25433.108.255.25565,534
11033.109.0.0/1633.109.0.1 to 33.109.255.25433.109.255.25565,534
11133.110.0.0/1633.110.0.1 to 33.110.255.25433.110.255.25565,534
11233.111.0.0/1633.111.0.1 to 33.111.255.25433.111.255.25565,534
11333.112.0.0/1633.112.0.1 to 33.112.255.25433.112.255.25565,534
11433.113.0.0/1633.113.0.1 to 33.113.255.25433.113.255.25565,534
11533.114.0.0/1633.114.0.1 to 33.114.255.25433.114.255.25565,534
11633.115.0.0/1633.115.0.1 to 33.115.255.25433.115.255.25565,534
11733.116.0.0/1633.116.0.1 to 33.116.255.25433.116.255.25565,534
11833.117.0.0/1633.117.0.1 to 33.117.255.25433.117.255.25565,534
11933.118.0.0/1633.118.0.1 to 33.118.255.25433.118.255.25565,534
12033.119.0.0/1633.119.0.1 to 33.119.255.25433.119.255.25565,534
12133.120.0.0/1633.120.0.1 to 33.120.255.25433.120.255.25565,534
12233.121.0.0/1633.121.0.1 to 33.121.255.25433.121.255.25565,534
12333.122.0.0/1633.122.0.1 to 33.122.255.25433.122.255.25565,534
12433.123.0.0/1633.123.0.1 to 33.123.255.25433.123.255.25565,534
12533.124.0.0/1633.124.0.1 to 33.124.255.25433.124.255.25565,534
12633.125.0.0/1633.125.0.1 to 33.125.255.25433.125.255.25565,534
12733.126.0.0/1633.126.0.1 to 33.126.255.25433.126.255.25565,534
12833.127.0.0/1633.127.0.1 to 33.127.255.25433.127.255.25565,534

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.