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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.

Network56.0.0.0/5
Usable hosts134,217,726
Subnet mask248.0.0.0
Addresses134,217,728
Network address
56.0.0.0
Broadcast address
63.255.255.255
First usable
56.0.0.1
Last usable
63.255.255.254
Usable hosts
134,217,726 (134,217,728 less the network and broadcast addresses)
Subnet mask
248.0.0.0
Wildcard mask
7.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/5
Type
Public public
Old class
A (default /8)
As numbers
Hex 38000000 · Integer 939524096 to 1073741823
Reverse DNS zones
56.in-addr.arpa
57.in-addr.arpa
58.in-addr.arpa
59.in-addr.arpa
60.in-addr.arpa
61.in-addr.arpa
62.in-addr.arpa
63.in-addr.arpa
/5 is not on a 8-bit boundary, so it takes 8 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00111000.00000000.00000000.0000000056.0.0.0
Subnet mask11111000.00000000.00000000.00000000248.0.0.0
Network00111000.00000000.00000000.0000000056.0.0.0
Broadcast00111111.11111111.11111111.1111111163.255.255.255
Split into smaller subnets/12
/6 (2)/7 (4)/8 (8)/9 (16)/10 (32)/11 (64)/12 (128)/13 (256)/14 (512)/15 (1,024)/16 (2,048)/17 (4,096)

56.0.0.0/5 makes 128 subnets of /12.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
156.0.0.0/1256.0.0.1 to 56.15.255.25456.15.255.2551,048,574
256.16.0.0/1256.16.0.1 to 56.31.255.25456.31.255.2551,048,574
356.32.0.0/1256.32.0.1 to 56.47.255.25456.47.255.2551,048,574
456.48.0.0/1256.48.0.1 to 56.63.255.25456.63.255.2551,048,574
556.64.0.0/1256.64.0.1 to 56.79.255.25456.79.255.2551,048,574
656.80.0.0/1256.80.0.1 to 56.95.255.25456.95.255.2551,048,574
756.96.0.0/1256.96.0.1 to 56.111.255.25456.111.255.2551,048,574
856.112.0.0/1256.112.0.1 to 56.127.255.25456.127.255.2551,048,574
956.128.0.0/1256.128.0.1 to 56.143.255.25456.143.255.2551,048,574
1056.144.0.0/1256.144.0.1 to 56.159.255.25456.159.255.2551,048,574
1156.160.0.0/1256.160.0.1 to 56.175.255.25456.175.255.2551,048,574
1256.176.0.0/1256.176.0.1 to 56.191.255.25456.191.255.2551,048,574
1356.192.0.0/1256.192.0.1 to 56.207.255.25456.207.255.2551,048,574
1456.208.0.0/1256.208.0.1 to 56.223.255.25456.223.255.2551,048,574
1556.224.0.0/1256.224.0.1 to 56.239.255.25456.239.255.2551,048,574
1656.240.0.0/1256.240.0.1 to 56.255.255.25456.255.255.2551,048,574
1757.0.0.0/1257.0.0.1 to 57.15.255.25457.15.255.2551,048,574
1857.16.0.0/1257.16.0.1 to 57.31.255.25457.31.255.2551,048,574
1957.32.0.0/1257.32.0.1 to 57.47.255.25457.47.255.2551,048,574
2057.48.0.0/1257.48.0.1 to 57.63.255.25457.63.255.2551,048,574
2157.64.0.0/1257.64.0.1 to 57.79.255.25457.79.255.2551,048,574
2257.80.0.0/1257.80.0.1 to 57.95.255.25457.95.255.2551,048,574
2357.96.0.0/1257.96.0.1 to 57.111.255.25457.111.255.2551,048,574
2457.112.0.0/1257.112.0.1 to 57.127.255.25457.127.255.2551,048,574
2557.128.0.0/1257.128.0.1 to 57.143.255.25457.143.255.2551,048,574
2657.144.0.0/1257.144.0.1 to 57.159.255.25457.159.255.2551,048,574
2757.160.0.0/1257.160.0.1 to 57.175.255.25457.175.255.2551,048,574
2857.176.0.0/1257.176.0.1 to 57.191.255.25457.191.255.2551,048,574
2957.192.0.0/1257.192.0.1 to 57.207.255.25457.207.255.2551,048,574
3057.208.0.0/1257.208.0.1 to 57.223.255.25457.223.255.2551,048,574
3157.224.0.0/1257.224.0.1 to 57.239.255.25457.239.255.2551,048,574
3257.240.0.0/1257.240.0.1 to 57.255.255.25457.255.255.2551,048,574
3358.0.0.0/1258.0.0.1 to 58.15.255.25458.15.255.2551,048,574
3458.16.0.0/1258.16.0.1 to 58.31.255.25458.31.255.2551,048,574
3558.32.0.0/1258.32.0.1 to 58.47.255.25458.47.255.2551,048,574
3658.48.0.0/1258.48.0.1 to 58.63.255.25458.63.255.2551,048,574
3758.64.0.0/1258.64.0.1 to 58.79.255.25458.79.255.2551,048,574
3858.80.0.0/1258.80.0.1 to 58.95.255.25458.95.255.2551,048,574
3958.96.0.0/1258.96.0.1 to 58.111.255.25458.111.255.2551,048,574
4058.112.0.0/1258.112.0.1 to 58.127.255.25458.127.255.2551,048,574
4158.128.0.0/1258.128.0.1 to 58.143.255.25458.143.255.2551,048,574
4258.144.0.0/1258.144.0.1 to 58.159.255.25458.159.255.2551,048,574
4358.160.0.0/1258.160.0.1 to 58.175.255.25458.175.255.2551,048,574
4458.176.0.0/1258.176.0.1 to 58.191.255.25458.191.255.2551,048,574
4558.192.0.0/1258.192.0.1 to 58.207.255.25458.207.255.2551,048,574
4658.208.0.0/1258.208.0.1 to 58.223.255.25458.223.255.2551,048,574
4758.224.0.0/1258.224.0.1 to 58.239.255.25458.239.255.2551,048,574
4858.240.0.0/1258.240.0.1 to 58.255.255.25458.255.255.2551,048,574
4959.0.0.0/1259.0.0.1 to 59.15.255.25459.15.255.2551,048,574
5059.16.0.0/1259.16.0.1 to 59.31.255.25459.31.255.2551,048,574
5159.32.0.0/1259.32.0.1 to 59.47.255.25459.47.255.2551,048,574
5259.48.0.0/1259.48.0.1 to 59.63.255.25459.63.255.2551,048,574
5359.64.0.0/1259.64.0.1 to 59.79.255.25459.79.255.2551,048,574
5459.80.0.0/1259.80.0.1 to 59.95.255.25459.95.255.2551,048,574
5559.96.0.0/1259.96.0.1 to 59.111.255.25459.111.255.2551,048,574
5659.112.0.0/1259.112.0.1 to 59.127.255.25459.127.255.2551,048,574
5759.128.0.0/1259.128.0.1 to 59.143.255.25459.143.255.2551,048,574
5859.144.0.0/1259.144.0.1 to 59.159.255.25459.159.255.2551,048,574
5959.160.0.0/1259.160.0.1 to 59.175.255.25459.175.255.2551,048,574
6059.176.0.0/1259.176.0.1 to 59.191.255.25459.191.255.2551,048,574
6159.192.0.0/1259.192.0.1 to 59.207.255.25459.207.255.2551,048,574
6259.208.0.0/1259.208.0.1 to 59.223.255.25459.223.255.2551,048,574
6359.224.0.0/1259.224.0.1 to 59.239.255.25459.239.255.2551,048,574
6459.240.0.0/1259.240.0.1 to 59.255.255.25459.255.255.2551,048,574
6560.0.0.0/1260.0.0.1 to 60.15.255.25460.15.255.2551,048,574
6660.16.0.0/1260.16.0.1 to 60.31.255.25460.31.255.2551,048,574
6760.32.0.0/1260.32.0.1 to 60.47.255.25460.47.255.2551,048,574
6860.48.0.0/1260.48.0.1 to 60.63.255.25460.63.255.2551,048,574
6960.64.0.0/1260.64.0.1 to 60.79.255.25460.79.255.2551,048,574
7060.80.0.0/1260.80.0.1 to 60.95.255.25460.95.255.2551,048,574
7160.96.0.0/1260.96.0.1 to 60.111.255.25460.111.255.2551,048,574
7260.112.0.0/1260.112.0.1 to 60.127.255.25460.127.255.2551,048,574
7360.128.0.0/1260.128.0.1 to 60.143.255.25460.143.255.2551,048,574
7460.144.0.0/1260.144.0.1 to 60.159.255.25460.159.255.2551,048,574
7560.160.0.0/1260.160.0.1 to 60.175.255.25460.175.255.2551,048,574
7660.176.0.0/1260.176.0.1 to 60.191.255.25460.191.255.2551,048,574
7760.192.0.0/1260.192.0.1 to 60.207.255.25460.207.255.2551,048,574
7860.208.0.0/1260.208.0.1 to 60.223.255.25460.223.255.2551,048,574
7960.224.0.0/1260.224.0.1 to 60.239.255.25460.239.255.2551,048,574
8060.240.0.0/1260.240.0.1 to 60.255.255.25460.255.255.2551,048,574
8161.0.0.0/1261.0.0.1 to 61.15.255.25461.15.255.2551,048,574
8261.16.0.0/1261.16.0.1 to 61.31.255.25461.31.255.2551,048,574
8361.32.0.0/1261.32.0.1 to 61.47.255.25461.47.255.2551,048,574
8461.48.0.0/1261.48.0.1 to 61.63.255.25461.63.255.2551,048,574
8561.64.0.0/1261.64.0.1 to 61.79.255.25461.79.255.2551,048,574
8661.80.0.0/1261.80.0.1 to 61.95.255.25461.95.255.2551,048,574
8761.96.0.0/1261.96.0.1 to 61.111.255.25461.111.255.2551,048,574
8861.112.0.0/1261.112.0.1 to 61.127.255.25461.127.255.2551,048,574
8961.128.0.0/1261.128.0.1 to 61.143.255.25461.143.255.2551,048,574
9061.144.0.0/1261.144.0.1 to 61.159.255.25461.159.255.2551,048,574
9161.160.0.0/1261.160.0.1 to 61.175.255.25461.175.255.2551,048,574
9261.176.0.0/1261.176.0.1 to 61.191.255.25461.191.255.2551,048,574
9361.192.0.0/1261.192.0.1 to 61.207.255.25461.207.255.2551,048,574
9461.208.0.0/1261.208.0.1 to 61.223.255.25461.223.255.2551,048,574
9561.224.0.0/1261.224.0.1 to 61.239.255.25461.239.255.2551,048,574
9661.240.0.0/1261.240.0.1 to 61.255.255.25461.255.255.2551,048,574
9762.0.0.0/1262.0.0.1 to 62.15.255.25462.15.255.2551,048,574
9862.16.0.0/1262.16.0.1 to 62.31.255.25462.31.255.2551,048,574
9962.32.0.0/1262.32.0.1 to 62.47.255.25462.47.255.2551,048,574
10062.48.0.0/1262.48.0.1 to 62.63.255.25462.63.255.2551,048,574
10162.64.0.0/1262.64.0.1 to 62.79.255.25462.79.255.2551,048,574
10262.80.0.0/1262.80.0.1 to 62.95.255.25462.95.255.2551,048,574
10362.96.0.0/1262.96.0.1 to 62.111.255.25462.111.255.2551,048,574
10462.112.0.0/1262.112.0.1 to 62.127.255.25462.127.255.2551,048,574
10562.128.0.0/1262.128.0.1 to 62.143.255.25462.143.255.2551,048,574
10662.144.0.0/1262.144.0.1 to 62.159.255.25462.159.255.2551,048,574
10762.160.0.0/1262.160.0.1 to 62.175.255.25462.175.255.2551,048,574
10862.176.0.0/1262.176.0.1 to 62.191.255.25462.191.255.2551,048,574
10962.192.0.0/1262.192.0.1 to 62.207.255.25462.207.255.2551,048,574
11062.208.0.0/1262.208.0.1 to 62.223.255.25462.223.255.2551,048,574
11162.224.0.0/1262.224.0.1 to 62.239.255.25462.239.255.2551,048,574
11262.240.0.0/1262.240.0.1 to 62.255.255.25462.255.255.2551,048,574
11363.0.0.0/1263.0.0.1 to 63.15.255.25463.15.255.2551,048,574
11463.16.0.0/1263.16.0.1 to 63.31.255.25463.31.255.2551,048,574
11563.32.0.0/1263.32.0.1 to 63.47.255.25463.47.255.2551,048,574
11663.48.0.0/1263.48.0.1 to 63.63.255.25463.63.255.2551,048,574
11763.64.0.0/1263.64.0.1 to 63.79.255.25463.79.255.2551,048,574
11863.80.0.0/1263.80.0.1 to 63.95.255.25463.95.255.2551,048,574
11963.96.0.0/1263.96.0.1 to 63.111.255.25463.111.255.2551,048,574
12063.112.0.0/1263.112.0.1 to 63.127.255.25463.127.255.2551,048,574
12163.128.0.0/1263.128.0.1 to 63.143.255.25463.143.255.2551,048,574
12263.144.0.0/1263.144.0.1 to 63.159.255.25463.159.255.2551,048,574
12363.160.0.0/1263.160.0.1 to 63.175.255.25463.175.255.2551,048,574
12463.176.0.0/1263.176.0.1 to 63.191.255.25463.191.255.2551,048,574
12563.192.0.0/1263.192.0.1 to 63.207.255.25463.207.255.2551,048,574
12663.208.0.0/1263.208.0.1 to 63.223.255.25463.223.255.2551,048,574
12763.224.0.0/1263.224.0.1 to 63.239.255.25463.239.255.2551,048,574
12863.240.0.0/1263.240.0.1 to 63.255.255.25463.255.255.2551,048,574

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.