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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.

Network38.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
38.0.0.0
Broadcast address
38.127.255.255
First usable
38.0.0.1
Last usable
38.127.255.254
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 26000000 · Integer 637534208 to 645922815
Reverse DNS zones
0.38.in-addr.arpa
1.38.in-addr.arpa
2.38.in-addr.arpa
3.38.in-addr.arpa
4.38.in-addr.arpa
5.38.in-addr.arpa
6.38.in-addr.arpa
7.38.in-addr.arpa
8.38.in-addr.arpa
9.38.in-addr.arpa
10.38.in-addr.arpa
11.38.in-addr.arpa
12.38.in-addr.arpa
13.38.in-addr.arpa
14.38.in-addr.arpa
15.38.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
Address00100110.00000000.00000000.0000000038.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network00100110.00000000.00000000.0000000038.0.0.0
Broadcast00100110.01111111.11111111.1111111138.127.255.255
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)

38.0.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
138.0.0.0/1638.0.0.1 to 38.0.255.25438.0.255.25565,534
238.1.0.0/1638.1.0.1 to 38.1.255.25438.1.255.25565,534
338.2.0.0/1638.2.0.1 to 38.2.255.25438.2.255.25565,534
438.3.0.0/1638.3.0.1 to 38.3.255.25438.3.255.25565,534
538.4.0.0/1638.4.0.1 to 38.4.255.25438.4.255.25565,534
638.5.0.0/1638.5.0.1 to 38.5.255.25438.5.255.25565,534
738.6.0.0/1638.6.0.1 to 38.6.255.25438.6.255.25565,534
838.7.0.0/1638.7.0.1 to 38.7.255.25438.7.255.25565,534
938.8.0.0/1638.8.0.1 to 38.8.255.25438.8.255.25565,534
1038.9.0.0/1638.9.0.1 to 38.9.255.25438.9.255.25565,534
1138.10.0.0/1638.10.0.1 to 38.10.255.25438.10.255.25565,534
1238.11.0.0/1638.11.0.1 to 38.11.255.25438.11.255.25565,534
1338.12.0.0/1638.12.0.1 to 38.12.255.25438.12.255.25565,534
1438.13.0.0/1638.13.0.1 to 38.13.255.25438.13.255.25565,534
1538.14.0.0/1638.14.0.1 to 38.14.255.25438.14.255.25565,534
1638.15.0.0/1638.15.0.1 to 38.15.255.25438.15.255.25565,534
1738.16.0.0/1638.16.0.1 to 38.16.255.25438.16.255.25565,534
1838.17.0.0/1638.17.0.1 to 38.17.255.25438.17.255.25565,534
1938.18.0.0/1638.18.0.1 to 38.18.255.25438.18.255.25565,534
2038.19.0.0/1638.19.0.1 to 38.19.255.25438.19.255.25565,534
2138.20.0.0/1638.20.0.1 to 38.20.255.25438.20.255.25565,534
2238.21.0.0/1638.21.0.1 to 38.21.255.25438.21.255.25565,534
2338.22.0.0/1638.22.0.1 to 38.22.255.25438.22.255.25565,534
2438.23.0.0/1638.23.0.1 to 38.23.255.25438.23.255.25565,534
2538.24.0.0/1638.24.0.1 to 38.24.255.25438.24.255.25565,534
2638.25.0.0/1638.25.0.1 to 38.25.255.25438.25.255.25565,534
2738.26.0.0/1638.26.0.1 to 38.26.255.25438.26.255.25565,534
2838.27.0.0/1638.27.0.1 to 38.27.255.25438.27.255.25565,534
2938.28.0.0/1638.28.0.1 to 38.28.255.25438.28.255.25565,534
3038.29.0.0/1638.29.0.1 to 38.29.255.25438.29.255.25565,534
3138.30.0.0/1638.30.0.1 to 38.30.255.25438.30.255.25565,534
3238.31.0.0/1638.31.0.1 to 38.31.255.25438.31.255.25565,534
3338.32.0.0/1638.32.0.1 to 38.32.255.25438.32.255.25565,534
3438.33.0.0/1638.33.0.1 to 38.33.255.25438.33.255.25565,534
3538.34.0.0/1638.34.0.1 to 38.34.255.25438.34.255.25565,534
3638.35.0.0/1638.35.0.1 to 38.35.255.25438.35.255.25565,534
3738.36.0.0/1638.36.0.1 to 38.36.255.25438.36.255.25565,534
3838.37.0.0/1638.37.0.1 to 38.37.255.25438.37.255.25565,534
3938.38.0.0/1638.38.0.1 to 38.38.255.25438.38.255.25565,534
4038.39.0.0/1638.39.0.1 to 38.39.255.25438.39.255.25565,534
4138.40.0.0/1638.40.0.1 to 38.40.255.25438.40.255.25565,534
4238.41.0.0/1638.41.0.1 to 38.41.255.25438.41.255.25565,534
4338.42.0.0/1638.42.0.1 to 38.42.255.25438.42.255.25565,534
4438.43.0.0/1638.43.0.1 to 38.43.255.25438.43.255.25565,534
4538.44.0.0/1638.44.0.1 to 38.44.255.25438.44.255.25565,534
4638.45.0.0/1638.45.0.1 to 38.45.255.25438.45.255.25565,534
4738.46.0.0/1638.46.0.1 to 38.46.255.25438.46.255.25565,534
4838.47.0.0/1638.47.0.1 to 38.47.255.25438.47.255.25565,534
4938.48.0.0/1638.48.0.1 to 38.48.255.25438.48.255.25565,534
5038.49.0.0/1638.49.0.1 to 38.49.255.25438.49.255.25565,534
5138.50.0.0/1638.50.0.1 to 38.50.255.25438.50.255.25565,534
5238.51.0.0/1638.51.0.1 to 38.51.255.25438.51.255.25565,534
5338.52.0.0/1638.52.0.1 to 38.52.255.25438.52.255.25565,534
5438.53.0.0/1638.53.0.1 to 38.53.255.25438.53.255.25565,534
5538.54.0.0/1638.54.0.1 to 38.54.255.25438.54.255.25565,534
5638.55.0.0/1638.55.0.1 to 38.55.255.25438.55.255.25565,534
5738.56.0.0/1638.56.0.1 to 38.56.255.25438.56.255.25565,534
5838.57.0.0/1638.57.0.1 to 38.57.255.25438.57.255.25565,534
5938.58.0.0/1638.58.0.1 to 38.58.255.25438.58.255.25565,534
6038.59.0.0/1638.59.0.1 to 38.59.255.25438.59.255.25565,534
6138.60.0.0/1638.60.0.1 to 38.60.255.25438.60.255.25565,534
6238.61.0.0/1638.61.0.1 to 38.61.255.25438.61.255.25565,534
6338.62.0.0/1638.62.0.1 to 38.62.255.25438.62.255.25565,534
6438.63.0.0/1638.63.0.1 to 38.63.255.25438.63.255.25565,534
6538.64.0.0/1638.64.0.1 to 38.64.255.25438.64.255.25565,534
6638.65.0.0/1638.65.0.1 to 38.65.255.25438.65.255.25565,534
6738.66.0.0/1638.66.0.1 to 38.66.255.25438.66.255.25565,534
6838.67.0.0/1638.67.0.1 to 38.67.255.25438.67.255.25565,534
6938.68.0.0/1638.68.0.1 to 38.68.255.25438.68.255.25565,534
7038.69.0.0/1638.69.0.1 to 38.69.255.25438.69.255.25565,534
7138.70.0.0/1638.70.0.1 to 38.70.255.25438.70.255.25565,534
7238.71.0.0/1638.71.0.1 to 38.71.255.25438.71.255.25565,534
7338.72.0.0/1638.72.0.1 to 38.72.255.25438.72.255.25565,534
7438.73.0.0/1638.73.0.1 to 38.73.255.25438.73.255.25565,534
7538.74.0.0/1638.74.0.1 to 38.74.255.25438.74.255.25565,534
7638.75.0.0/1638.75.0.1 to 38.75.255.25438.75.255.25565,534
7738.76.0.0/1638.76.0.1 to 38.76.255.25438.76.255.25565,534
7838.77.0.0/1638.77.0.1 to 38.77.255.25438.77.255.25565,534
7938.78.0.0/1638.78.0.1 to 38.78.255.25438.78.255.25565,534
8038.79.0.0/1638.79.0.1 to 38.79.255.25438.79.255.25565,534
8138.80.0.0/1638.80.0.1 to 38.80.255.25438.80.255.25565,534
8238.81.0.0/1638.81.0.1 to 38.81.255.25438.81.255.25565,534
8338.82.0.0/1638.82.0.1 to 38.82.255.25438.82.255.25565,534
8438.83.0.0/1638.83.0.1 to 38.83.255.25438.83.255.25565,534
8538.84.0.0/1638.84.0.1 to 38.84.255.25438.84.255.25565,534
8638.85.0.0/1638.85.0.1 to 38.85.255.25438.85.255.25565,534
8738.86.0.0/1638.86.0.1 to 38.86.255.25438.86.255.25565,534
8838.87.0.0/1638.87.0.1 to 38.87.255.25438.87.255.25565,534
8938.88.0.0/1638.88.0.1 to 38.88.255.25438.88.255.25565,534
9038.89.0.0/1638.89.0.1 to 38.89.255.25438.89.255.25565,534
9138.90.0.0/1638.90.0.1 to 38.90.255.25438.90.255.25565,534
9238.91.0.0/1638.91.0.1 to 38.91.255.25438.91.255.25565,534
9338.92.0.0/1638.92.0.1 to 38.92.255.25438.92.255.25565,534
9438.93.0.0/1638.93.0.1 to 38.93.255.25438.93.255.25565,534
9538.94.0.0/1638.94.0.1 to 38.94.255.25438.94.255.25565,534
9638.95.0.0/1638.95.0.1 to 38.95.255.25438.95.255.25565,534
9738.96.0.0/1638.96.0.1 to 38.96.255.25438.96.255.25565,534
9838.97.0.0/1638.97.0.1 to 38.97.255.25438.97.255.25565,534
9938.98.0.0/1638.98.0.1 to 38.98.255.25438.98.255.25565,534
10038.99.0.0/1638.99.0.1 to 38.99.255.25438.99.255.25565,534
10138.100.0.0/1638.100.0.1 to 38.100.255.25438.100.255.25565,534
10238.101.0.0/1638.101.0.1 to 38.101.255.25438.101.255.25565,534
10338.102.0.0/1638.102.0.1 to 38.102.255.25438.102.255.25565,534
10438.103.0.0/1638.103.0.1 to 38.103.255.25438.103.255.25565,534
10538.104.0.0/1638.104.0.1 to 38.104.255.25438.104.255.25565,534
10638.105.0.0/1638.105.0.1 to 38.105.255.25438.105.255.25565,534
10738.106.0.0/1638.106.0.1 to 38.106.255.25438.106.255.25565,534
10838.107.0.0/1638.107.0.1 to 38.107.255.25438.107.255.25565,534
10938.108.0.0/1638.108.0.1 to 38.108.255.25438.108.255.25565,534
11038.109.0.0/1638.109.0.1 to 38.109.255.25438.109.255.25565,534
11138.110.0.0/1638.110.0.1 to 38.110.255.25438.110.255.25565,534
11238.111.0.0/1638.111.0.1 to 38.111.255.25438.111.255.25565,534
11338.112.0.0/1638.112.0.1 to 38.112.255.25438.112.255.25565,534
11438.113.0.0/1638.113.0.1 to 38.113.255.25438.113.255.25565,534
11538.114.0.0/1638.114.0.1 to 38.114.255.25438.114.255.25565,534
11638.115.0.0/1638.115.0.1 to 38.115.255.25438.115.255.25565,534
11738.116.0.0/1638.116.0.1 to 38.116.255.25438.116.255.25565,534
11838.117.0.0/1638.117.0.1 to 38.117.255.25438.117.255.25565,534
11938.118.0.0/1638.118.0.1 to 38.118.255.25438.118.255.25565,534
12038.119.0.0/1638.119.0.1 to 38.119.255.25438.119.255.25565,534
12138.120.0.0/1638.120.0.1 to 38.120.255.25438.120.255.25565,534
12238.121.0.0/1638.121.0.1 to 38.121.255.25438.121.255.25565,534
12338.122.0.0/1638.122.0.1 to 38.122.255.25438.122.255.25565,534
12438.123.0.0/1638.123.0.1 to 38.123.255.25438.123.255.25565,534
12538.124.0.0/1638.124.0.1 to 38.124.255.25438.124.255.25565,534
12638.125.0.0/1638.125.0.1 to 38.125.255.25438.125.255.25565,534
12738.126.0.0/1638.126.0.1 to 38.126.255.25438.126.255.25565,534
12838.127.0.0/1638.127.0.1 to 38.127.255.25438.127.255.25565,534

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.