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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.

Network45.0.0.0/9
Usable hosts8,388,606
Subnet mask255.128.0.0
Addresses8,388,608
Network address
45.0.0.0
Broadcast address
45.127.255.255
First usable
45.0.0.1
Last usable
45.127.255.254
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 2D000000 · Integer 754974720 to 763363327
Reverse DNS zones
0.45.in-addr.arpa
1.45.in-addr.arpa
2.45.in-addr.arpa
3.45.in-addr.arpa
4.45.in-addr.arpa
5.45.in-addr.arpa
6.45.in-addr.arpa
7.45.in-addr.arpa
8.45.in-addr.arpa
9.45.in-addr.arpa
10.45.in-addr.arpa
11.45.in-addr.arpa
12.45.in-addr.arpa
13.45.in-addr.arpa
14.45.in-addr.arpa
15.45.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
Address00101101.00000000.00000000.0000000045.0.0.0
Subnet mask11111111.10000000.00000000.00000000255.128.0.0
Network00101101.00000000.00000000.0000000045.0.0.0
Broadcast00101101.01111111.11111111.1111111145.127.255.255
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)

45.0.0.0/9 makes 128 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
145.0.0.0/1645.0.0.1 to 45.0.255.25445.0.255.25565,534
245.1.0.0/1645.1.0.1 to 45.1.255.25445.1.255.25565,534
345.2.0.0/1645.2.0.1 to 45.2.255.25445.2.255.25565,534
445.3.0.0/1645.3.0.1 to 45.3.255.25445.3.255.25565,534
545.4.0.0/1645.4.0.1 to 45.4.255.25445.4.255.25565,534
645.5.0.0/1645.5.0.1 to 45.5.255.25445.5.255.25565,534
745.6.0.0/1645.6.0.1 to 45.6.255.25445.6.255.25565,534
845.7.0.0/1645.7.0.1 to 45.7.255.25445.7.255.25565,534
945.8.0.0/1645.8.0.1 to 45.8.255.25445.8.255.25565,534
1045.9.0.0/1645.9.0.1 to 45.9.255.25445.9.255.25565,534
1145.10.0.0/1645.10.0.1 to 45.10.255.25445.10.255.25565,534
1245.11.0.0/1645.11.0.1 to 45.11.255.25445.11.255.25565,534
1345.12.0.0/1645.12.0.1 to 45.12.255.25445.12.255.25565,534
1445.13.0.0/1645.13.0.1 to 45.13.255.25445.13.255.25565,534
1545.14.0.0/1645.14.0.1 to 45.14.255.25445.14.255.25565,534
1645.15.0.0/1645.15.0.1 to 45.15.255.25445.15.255.25565,534
1745.16.0.0/1645.16.0.1 to 45.16.255.25445.16.255.25565,534
1845.17.0.0/1645.17.0.1 to 45.17.255.25445.17.255.25565,534
1945.18.0.0/1645.18.0.1 to 45.18.255.25445.18.255.25565,534
2045.19.0.0/1645.19.0.1 to 45.19.255.25445.19.255.25565,534
2145.20.0.0/1645.20.0.1 to 45.20.255.25445.20.255.25565,534
2245.21.0.0/1645.21.0.1 to 45.21.255.25445.21.255.25565,534
2345.22.0.0/1645.22.0.1 to 45.22.255.25445.22.255.25565,534
2445.23.0.0/1645.23.0.1 to 45.23.255.25445.23.255.25565,534
2545.24.0.0/1645.24.0.1 to 45.24.255.25445.24.255.25565,534
2645.25.0.0/1645.25.0.1 to 45.25.255.25445.25.255.25565,534
2745.26.0.0/1645.26.0.1 to 45.26.255.25445.26.255.25565,534
2845.27.0.0/1645.27.0.1 to 45.27.255.25445.27.255.25565,534
2945.28.0.0/1645.28.0.1 to 45.28.255.25445.28.255.25565,534
3045.29.0.0/1645.29.0.1 to 45.29.255.25445.29.255.25565,534
3145.30.0.0/1645.30.0.1 to 45.30.255.25445.30.255.25565,534
3245.31.0.0/1645.31.0.1 to 45.31.255.25445.31.255.25565,534
3345.32.0.0/1645.32.0.1 to 45.32.255.25445.32.255.25565,534
3445.33.0.0/1645.33.0.1 to 45.33.255.25445.33.255.25565,534
3545.34.0.0/1645.34.0.1 to 45.34.255.25445.34.255.25565,534
3645.35.0.0/1645.35.0.1 to 45.35.255.25445.35.255.25565,534
3745.36.0.0/1645.36.0.1 to 45.36.255.25445.36.255.25565,534
3845.37.0.0/1645.37.0.1 to 45.37.255.25445.37.255.25565,534
3945.38.0.0/1645.38.0.1 to 45.38.255.25445.38.255.25565,534
4045.39.0.0/1645.39.0.1 to 45.39.255.25445.39.255.25565,534
4145.40.0.0/1645.40.0.1 to 45.40.255.25445.40.255.25565,534
4245.41.0.0/1645.41.0.1 to 45.41.255.25445.41.255.25565,534
4345.42.0.0/1645.42.0.1 to 45.42.255.25445.42.255.25565,534
4445.43.0.0/1645.43.0.1 to 45.43.255.25445.43.255.25565,534
4545.44.0.0/1645.44.0.1 to 45.44.255.25445.44.255.25565,534
4645.45.0.0/1645.45.0.1 to 45.45.255.25445.45.255.25565,534
4745.46.0.0/1645.46.0.1 to 45.46.255.25445.46.255.25565,534
4845.47.0.0/1645.47.0.1 to 45.47.255.25445.47.255.25565,534
4945.48.0.0/1645.48.0.1 to 45.48.255.25445.48.255.25565,534
5045.49.0.0/1645.49.0.1 to 45.49.255.25445.49.255.25565,534
5145.50.0.0/1645.50.0.1 to 45.50.255.25445.50.255.25565,534
5245.51.0.0/1645.51.0.1 to 45.51.255.25445.51.255.25565,534
5345.52.0.0/1645.52.0.1 to 45.52.255.25445.52.255.25565,534
5445.53.0.0/1645.53.0.1 to 45.53.255.25445.53.255.25565,534
5545.54.0.0/1645.54.0.1 to 45.54.255.25445.54.255.25565,534
5645.55.0.0/1645.55.0.1 to 45.55.255.25445.55.255.25565,534
5745.56.0.0/1645.56.0.1 to 45.56.255.25445.56.255.25565,534
5845.57.0.0/1645.57.0.1 to 45.57.255.25445.57.255.25565,534
5945.58.0.0/1645.58.0.1 to 45.58.255.25445.58.255.25565,534
6045.59.0.0/1645.59.0.1 to 45.59.255.25445.59.255.25565,534
6145.60.0.0/1645.60.0.1 to 45.60.255.25445.60.255.25565,534
6245.61.0.0/1645.61.0.1 to 45.61.255.25445.61.255.25565,534
6345.62.0.0/1645.62.0.1 to 45.62.255.25445.62.255.25565,534
6445.63.0.0/1645.63.0.1 to 45.63.255.25445.63.255.25565,534
6545.64.0.0/1645.64.0.1 to 45.64.255.25445.64.255.25565,534
6645.65.0.0/1645.65.0.1 to 45.65.255.25445.65.255.25565,534
6745.66.0.0/1645.66.0.1 to 45.66.255.25445.66.255.25565,534
6845.67.0.0/1645.67.0.1 to 45.67.255.25445.67.255.25565,534
6945.68.0.0/1645.68.0.1 to 45.68.255.25445.68.255.25565,534
7045.69.0.0/1645.69.0.1 to 45.69.255.25445.69.255.25565,534
7145.70.0.0/1645.70.0.1 to 45.70.255.25445.70.255.25565,534
7245.71.0.0/1645.71.0.1 to 45.71.255.25445.71.255.25565,534
7345.72.0.0/1645.72.0.1 to 45.72.255.25445.72.255.25565,534
7445.73.0.0/1645.73.0.1 to 45.73.255.25445.73.255.25565,534
7545.74.0.0/1645.74.0.1 to 45.74.255.25445.74.255.25565,534
7645.75.0.0/1645.75.0.1 to 45.75.255.25445.75.255.25565,534
7745.76.0.0/1645.76.0.1 to 45.76.255.25445.76.255.25565,534
7845.77.0.0/1645.77.0.1 to 45.77.255.25445.77.255.25565,534
7945.78.0.0/1645.78.0.1 to 45.78.255.25445.78.255.25565,534
8045.79.0.0/1645.79.0.1 to 45.79.255.25445.79.255.25565,534
8145.80.0.0/1645.80.0.1 to 45.80.255.25445.80.255.25565,534
8245.81.0.0/1645.81.0.1 to 45.81.255.25445.81.255.25565,534
8345.82.0.0/1645.82.0.1 to 45.82.255.25445.82.255.25565,534
8445.83.0.0/1645.83.0.1 to 45.83.255.25445.83.255.25565,534
8545.84.0.0/1645.84.0.1 to 45.84.255.25445.84.255.25565,534
8645.85.0.0/1645.85.0.1 to 45.85.255.25445.85.255.25565,534
8745.86.0.0/1645.86.0.1 to 45.86.255.25445.86.255.25565,534
8845.87.0.0/1645.87.0.1 to 45.87.255.25445.87.255.25565,534
8945.88.0.0/1645.88.0.1 to 45.88.255.25445.88.255.25565,534
9045.89.0.0/1645.89.0.1 to 45.89.255.25445.89.255.25565,534
9145.90.0.0/1645.90.0.1 to 45.90.255.25445.90.255.25565,534
9245.91.0.0/1645.91.0.1 to 45.91.255.25445.91.255.25565,534
9345.92.0.0/1645.92.0.1 to 45.92.255.25445.92.255.25565,534
9445.93.0.0/1645.93.0.1 to 45.93.255.25445.93.255.25565,534
9545.94.0.0/1645.94.0.1 to 45.94.255.25445.94.255.25565,534
9645.95.0.0/1645.95.0.1 to 45.95.255.25445.95.255.25565,534
9745.96.0.0/1645.96.0.1 to 45.96.255.25445.96.255.25565,534
9845.97.0.0/1645.97.0.1 to 45.97.255.25445.97.255.25565,534
9945.98.0.0/1645.98.0.1 to 45.98.255.25445.98.255.25565,534
10045.99.0.0/1645.99.0.1 to 45.99.255.25445.99.255.25565,534
10145.100.0.0/1645.100.0.1 to 45.100.255.25445.100.255.25565,534
10245.101.0.0/1645.101.0.1 to 45.101.255.25445.101.255.25565,534
10345.102.0.0/1645.102.0.1 to 45.102.255.25445.102.255.25565,534
10445.103.0.0/1645.103.0.1 to 45.103.255.25445.103.255.25565,534
10545.104.0.0/1645.104.0.1 to 45.104.255.25445.104.255.25565,534
10645.105.0.0/1645.105.0.1 to 45.105.255.25445.105.255.25565,534
10745.106.0.0/1645.106.0.1 to 45.106.255.25445.106.255.25565,534
10845.107.0.0/1645.107.0.1 to 45.107.255.25445.107.255.25565,534
10945.108.0.0/1645.108.0.1 to 45.108.255.25445.108.255.25565,534
11045.109.0.0/1645.109.0.1 to 45.109.255.25445.109.255.25565,534
11145.110.0.0/1645.110.0.1 to 45.110.255.25445.110.255.25565,534
11245.111.0.0/1645.111.0.1 to 45.111.255.25445.111.255.25565,534
11345.112.0.0/1645.112.0.1 to 45.112.255.25445.112.255.25565,534
11445.113.0.0/1645.113.0.1 to 45.113.255.25445.113.255.25565,534
11545.114.0.0/1645.114.0.1 to 45.114.255.25445.114.255.25565,534
11645.115.0.0/1645.115.0.1 to 45.115.255.25445.115.255.25565,534
11745.116.0.0/1645.116.0.1 to 45.116.255.25445.116.255.25565,534
11845.117.0.0/1645.117.0.1 to 45.117.255.25445.117.255.25565,534
11945.118.0.0/1645.118.0.1 to 45.118.255.25445.118.255.25565,534
12045.119.0.0/1645.119.0.1 to 45.119.255.25445.119.255.25565,534
12145.120.0.0/1645.120.0.1 to 45.120.255.25445.120.255.25565,534
12245.121.0.0/1645.121.0.1 to 45.121.255.25445.121.255.25565,534
12345.122.0.0/1645.122.0.1 to 45.122.255.25445.122.255.25565,534
12445.123.0.0/1645.123.0.1 to 45.123.255.25445.123.255.25565,534
12545.124.0.0/1645.124.0.1 to 45.124.255.25445.124.255.25565,534
12645.125.0.0/1645.125.0.1 to 45.125.255.25445.125.255.25565,534
12745.126.0.0/1645.126.0.1 to 45.126.255.25445.126.255.25565,534
12845.127.0.0/1645.127.0.1 to 45.127.255.25445.127.255.25565,534

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.