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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.

Network66.64.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
66.64.0.0
Broadcast address
66.127.255.255
First usable
66.64.0.1
Last usable
66.127.255.254
Usable hosts
4,194,302 (4,194,304 less the network and broadcast addresses)
Subnet mask
255.192.0.0
Wildcard mask
0.63.255.255 (Cisco ACLs, OSPF)
Prefix length
/10
Type
Public public
Old class
A (default /8)
As numbers
Hex 42400000 · Integer 1111490560 to 1115684863
Reverse DNS zones
64.66.in-addr.arpa
65.66.in-addr.arpa
66.66.in-addr.arpa
67.66.in-addr.arpa
68.66.in-addr.arpa
69.66.in-addr.arpa
70.66.in-addr.arpa
71.66.in-addr.arpa
72.66.in-addr.arpa
73.66.in-addr.arpa
74.66.in-addr.arpa
75.66.in-addr.arpa
76.66.in-addr.arpa
77.66.in-addr.arpa
78.66.in-addr.arpa
79.66.in-addr.arpa
and 48 more
/10 is not on a 8-bit boundary, so it takes 64 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01000010.01000000.00000000.0000000066.64.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network01000010.01000000.00000000.0000000066.64.0.0
Broadcast01000010.01111111.11111111.1111111166.127.255.255
Split into smaller subnets/17
/11 (2)/12 (4)/13 (8)/14 (16)/15 (32)/16 (64)/17 (128)/18 (256)/19 (512)/20 (1,024)/21 (2,048)/22 (4,096)

66.64.0.0/10 makes 128 subnets of /17.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
166.64.0.0/1766.64.0.1 to 66.64.127.25466.64.127.25532,766
266.64.128.0/1766.64.128.1 to 66.64.255.25466.64.255.25532,766
366.65.0.0/1766.65.0.1 to 66.65.127.25466.65.127.25532,766
466.65.128.0/1766.65.128.1 to 66.65.255.25466.65.255.25532,766
566.66.0.0/1766.66.0.1 to 66.66.127.25466.66.127.25532,766
666.66.128.0/1766.66.128.1 to 66.66.255.25466.66.255.25532,766
766.67.0.0/1766.67.0.1 to 66.67.127.25466.67.127.25532,766
866.67.128.0/1766.67.128.1 to 66.67.255.25466.67.255.25532,766
966.68.0.0/1766.68.0.1 to 66.68.127.25466.68.127.25532,766
1066.68.128.0/1766.68.128.1 to 66.68.255.25466.68.255.25532,766
1166.69.0.0/1766.69.0.1 to 66.69.127.25466.69.127.25532,766
1266.69.128.0/1766.69.128.1 to 66.69.255.25466.69.255.25532,766
1366.70.0.0/1766.70.0.1 to 66.70.127.25466.70.127.25532,766
1466.70.128.0/1766.70.128.1 to 66.70.255.25466.70.255.25532,766
1566.71.0.0/1766.71.0.1 to 66.71.127.25466.71.127.25532,766
1666.71.128.0/1766.71.128.1 to 66.71.255.25466.71.255.25532,766
1766.72.0.0/1766.72.0.1 to 66.72.127.25466.72.127.25532,766
1866.72.128.0/1766.72.128.1 to 66.72.255.25466.72.255.25532,766
1966.73.0.0/1766.73.0.1 to 66.73.127.25466.73.127.25532,766
2066.73.128.0/1766.73.128.1 to 66.73.255.25466.73.255.25532,766
2166.74.0.0/1766.74.0.1 to 66.74.127.25466.74.127.25532,766
2266.74.128.0/1766.74.128.1 to 66.74.255.25466.74.255.25532,766
2366.75.0.0/1766.75.0.1 to 66.75.127.25466.75.127.25532,766
2466.75.128.0/1766.75.128.1 to 66.75.255.25466.75.255.25532,766
2566.76.0.0/1766.76.0.1 to 66.76.127.25466.76.127.25532,766
2666.76.128.0/1766.76.128.1 to 66.76.255.25466.76.255.25532,766
2766.77.0.0/1766.77.0.1 to 66.77.127.25466.77.127.25532,766
2866.77.128.0/1766.77.128.1 to 66.77.255.25466.77.255.25532,766
2966.78.0.0/1766.78.0.1 to 66.78.127.25466.78.127.25532,766
3066.78.128.0/1766.78.128.1 to 66.78.255.25466.78.255.25532,766
3166.79.0.0/1766.79.0.1 to 66.79.127.25466.79.127.25532,766
3266.79.128.0/1766.79.128.1 to 66.79.255.25466.79.255.25532,766
3366.80.0.0/1766.80.0.1 to 66.80.127.25466.80.127.25532,766
3466.80.128.0/1766.80.128.1 to 66.80.255.25466.80.255.25532,766
3566.81.0.0/1766.81.0.1 to 66.81.127.25466.81.127.25532,766
3666.81.128.0/1766.81.128.1 to 66.81.255.25466.81.255.25532,766
3766.82.0.0/1766.82.0.1 to 66.82.127.25466.82.127.25532,766
3866.82.128.0/1766.82.128.1 to 66.82.255.25466.82.255.25532,766
3966.83.0.0/1766.83.0.1 to 66.83.127.25466.83.127.25532,766
4066.83.128.0/1766.83.128.1 to 66.83.255.25466.83.255.25532,766
4166.84.0.0/1766.84.0.1 to 66.84.127.25466.84.127.25532,766
4266.84.128.0/1766.84.128.1 to 66.84.255.25466.84.255.25532,766
4366.85.0.0/1766.85.0.1 to 66.85.127.25466.85.127.25532,766
4466.85.128.0/1766.85.128.1 to 66.85.255.25466.85.255.25532,766
4566.86.0.0/1766.86.0.1 to 66.86.127.25466.86.127.25532,766
4666.86.128.0/1766.86.128.1 to 66.86.255.25466.86.255.25532,766
4766.87.0.0/1766.87.0.1 to 66.87.127.25466.87.127.25532,766
4866.87.128.0/1766.87.128.1 to 66.87.255.25466.87.255.25532,766
4966.88.0.0/1766.88.0.1 to 66.88.127.25466.88.127.25532,766
5066.88.128.0/1766.88.128.1 to 66.88.255.25466.88.255.25532,766
5166.89.0.0/1766.89.0.1 to 66.89.127.25466.89.127.25532,766
5266.89.128.0/1766.89.128.1 to 66.89.255.25466.89.255.25532,766
5366.90.0.0/1766.90.0.1 to 66.90.127.25466.90.127.25532,766
5466.90.128.0/1766.90.128.1 to 66.90.255.25466.90.255.25532,766
5566.91.0.0/1766.91.0.1 to 66.91.127.25466.91.127.25532,766
5666.91.128.0/1766.91.128.1 to 66.91.255.25466.91.255.25532,766
5766.92.0.0/1766.92.0.1 to 66.92.127.25466.92.127.25532,766
5866.92.128.0/1766.92.128.1 to 66.92.255.25466.92.255.25532,766
5966.93.0.0/1766.93.0.1 to 66.93.127.25466.93.127.25532,766
6066.93.128.0/1766.93.128.1 to 66.93.255.25466.93.255.25532,766
6166.94.0.0/1766.94.0.1 to 66.94.127.25466.94.127.25532,766
6266.94.128.0/1766.94.128.1 to 66.94.255.25466.94.255.25532,766
6366.95.0.0/1766.95.0.1 to 66.95.127.25466.95.127.25532,766
6466.95.128.0/1766.95.128.1 to 66.95.255.25466.95.255.25532,766
6566.96.0.0/1766.96.0.1 to 66.96.127.25466.96.127.25532,766
6666.96.128.0/1766.96.128.1 to 66.96.255.25466.96.255.25532,766
6766.97.0.0/1766.97.0.1 to 66.97.127.25466.97.127.25532,766
6866.97.128.0/1766.97.128.1 to 66.97.255.25466.97.255.25532,766
6966.98.0.0/1766.98.0.1 to 66.98.127.25466.98.127.25532,766
7066.98.128.0/1766.98.128.1 to 66.98.255.25466.98.255.25532,766
7166.99.0.0/1766.99.0.1 to 66.99.127.25466.99.127.25532,766
7266.99.128.0/1766.99.128.1 to 66.99.255.25466.99.255.25532,766
7366.100.0.0/1766.100.0.1 to 66.100.127.25466.100.127.25532,766
7466.100.128.0/1766.100.128.1 to 66.100.255.25466.100.255.25532,766
7566.101.0.0/1766.101.0.1 to 66.101.127.25466.101.127.25532,766
7666.101.128.0/1766.101.128.1 to 66.101.255.25466.101.255.25532,766
7766.102.0.0/1766.102.0.1 to 66.102.127.25466.102.127.25532,766
7866.102.128.0/1766.102.128.1 to 66.102.255.25466.102.255.25532,766
7966.103.0.0/1766.103.0.1 to 66.103.127.25466.103.127.25532,766
8066.103.128.0/1766.103.128.1 to 66.103.255.25466.103.255.25532,766
8166.104.0.0/1766.104.0.1 to 66.104.127.25466.104.127.25532,766
8266.104.128.0/1766.104.128.1 to 66.104.255.25466.104.255.25532,766
8366.105.0.0/1766.105.0.1 to 66.105.127.25466.105.127.25532,766
8466.105.128.0/1766.105.128.1 to 66.105.255.25466.105.255.25532,766
8566.106.0.0/1766.106.0.1 to 66.106.127.25466.106.127.25532,766
8666.106.128.0/1766.106.128.1 to 66.106.255.25466.106.255.25532,766
8766.107.0.0/1766.107.0.1 to 66.107.127.25466.107.127.25532,766
8866.107.128.0/1766.107.128.1 to 66.107.255.25466.107.255.25532,766
8966.108.0.0/1766.108.0.1 to 66.108.127.25466.108.127.25532,766
9066.108.128.0/1766.108.128.1 to 66.108.255.25466.108.255.25532,766
9166.109.0.0/1766.109.0.1 to 66.109.127.25466.109.127.25532,766
9266.109.128.0/1766.109.128.1 to 66.109.255.25466.109.255.25532,766
9366.110.0.0/1766.110.0.1 to 66.110.127.25466.110.127.25532,766
9466.110.128.0/1766.110.128.1 to 66.110.255.25466.110.255.25532,766
9566.111.0.0/1766.111.0.1 to 66.111.127.25466.111.127.25532,766
9666.111.128.0/1766.111.128.1 to 66.111.255.25466.111.255.25532,766
9766.112.0.0/1766.112.0.1 to 66.112.127.25466.112.127.25532,766
9866.112.128.0/1766.112.128.1 to 66.112.255.25466.112.255.25532,766
9966.113.0.0/1766.113.0.1 to 66.113.127.25466.113.127.25532,766
10066.113.128.0/1766.113.128.1 to 66.113.255.25466.113.255.25532,766
10166.114.0.0/1766.114.0.1 to 66.114.127.25466.114.127.25532,766
10266.114.128.0/1766.114.128.1 to 66.114.255.25466.114.255.25532,766
10366.115.0.0/1766.115.0.1 to 66.115.127.25466.115.127.25532,766
10466.115.128.0/1766.115.128.1 to 66.115.255.25466.115.255.25532,766
10566.116.0.0/1766.116.0.1 to 66.116.127.25466.116.127.25532,766
10666.116.128.0/1766.116.128.1 to 66.116.255.25466.116.255.25532,766
10766.117.0.0/1766.117.0.1 to 66.117.127.25466.117.127.25532,766
10866.117.128.0/1766.117.128.1 to 66.117.255.25466.117.255.25532,766
10966.118.0.0/1766.118.0.1 to 66.118.127.25466.118.127.25532,766
11066.118.128.0/1766.118.128.1 to 66.118.255.25466.118.255.25532,766
11166.119.0.0/1766.119.0.1 to 66.119.127.25466.119.127.25532,766
11266.119.128.0/1766.119.128.1 to 66.119.255.25466.119.255.25532,766
11366.120.0.0/1766.120.0.1 to 66.120.127.25466.120.127.25532,766
11466.120.128.0/1766.120.128.1 to 66.120.255.25466.120.255.25532,766
11566.121.0.0/1766.121.0.1 to 66.121.127.25466.121.127.25532,766
11666.121.128.0/1766.121.128.1 to 66.121.255.25466.121.255.25532,766
11766.122.0.0/1766.122.0.1 to 66.122.127.25466.122.127.25532,766
11866.122.128.0/1766.122.128.1 to 66.122.255.25466.122.255.25532,766
11966.123.0.0/1766.123.0.1 to 66.123.127.25466.123.127.25532,766
12066.123.128.0/1766.123.128.1 to 66.123.255.25466.123.255.25532,766
12166.124.0.0/1766.124.0.1 to 66.124.127.25466.124.127.25532,766
12266.124.128.0/1766.124.128.1 to 66.124.255.25466.124.255.25532,766
12366.125.0.0/1766.125.0.1 to 66.125.127.25466.125.127.25532,766
12466.125.128.0/1766.125.128.1 to 66.125.255.25466.125.255.25532,766
12566.126.0.0/1766.126.0.1 to 66.126.127.25466.126.127.25532,766
12666.126.128.0/1766.126.128.1 to 66.126.255.25466.126.255.25532,766
12766.127.0.0/1766.127.0.1 to 66.127.127.25466.127.127.25532,766
12866.127.128.0/1766.127.128.1 to 66.127.255.25466.127.255.25532,766

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.