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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.

Network40.64.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
40.64.0.0
Broadcast address
40.127.255.255
First usable
40.64.0.1
Last usable
40.127.255.254
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 28400000 · Integer 675282944 to 679477247
Reverse DNS zones
64.40.in-addr.arpa
65.40.in-addr.arpa
66.40.in-addr.arpa
67.40.in-addr.arpa
68.40.in-addr.arpa
69.40.in-addr.arpa
70.40.in-addr.arpa
71.40.in-addr.arpa
72.40.in-addr.arpa
73.40.in-addr.arpa
74.40.in-addr.arpa
75.40.in-addr.arpa
76.40.in-addr.arpa
77.40.in-addr.arpa
78.40.in-addr.arpa
79.40.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
Address00101000.01000000.00000000.0000000040.64.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network00101000.01000000.00000000.0000000040.64.0.0
Broadcast00101000.01111111.11111111.1111111140.127.255.255
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)

40.64.0.0/10 makes 128 subnets of /17.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
140.64.0.0/1740.64.0.1 to 40.64.127.25440.64.127.25532,766
240.64.128.0/1740.64.128.1 to 40.64.255.25440.64.255.25532,766
340.65.0.0/1740.65.0.1 to 40.65.127.25440.65.127.25532,766
440.65.128.0/1740.65.128.1 to 40.65.255.25440.65.255.25532,766
540.66.0.0/1740.66.0.1 to 40.66.127.25440.66.127.25532,766
640.66.128.0/1740.66.128.1 to 40.66.255.25440.66.255.25532,766
740.67.0.0/1740.67.0.1 to 40.67.127.25440.67.127.25532,766
840.67.128.0/1740.67.128.1 to 40.67.255.25440.67.255.25532,766
940.68.0.0/1740.68.0.1 to 40.68.127.25440.68.127.25532,766
1040.68.128.0/1740.68.128.1 to 40.68.255.25440.68.255.25532,766
1140.69.0.0/1740.69.0.1 to 40.69.127.25440.69.127.25532,766
1240.69.128.0/1740.69.128.1 to 40.69.255.25440.69.255.25532,766
1340.70.0.0/1740.70.0.1 to 40.70.127.25440.70.127.25532,766
1440.70.128.0/1740.70.128.1 to 40.70.255.25440.70.255.25532,766
1540.71.0.0/1740.71.0.1 to 40.71.127.25440.71.127.25532,766
1640.71.128.0/1740.71.128.1 to 40.71.255.25440.71.255.25532,766
1740.72.0.0/1740.72.0.1 to 40.72.127.25440.72.127.25532,766
1840.72.128.0/1740.72.128.1 to 40.72.255.25440.72.255.25532,766
1940.73.0.0/1740.73.0.1 to 40.73.127.25440.73.127.25532,766
2040.73.128.0/1740.73.128.1 to 40.73.255.25440.73.255.25532,766
2140.74.0.0/1740.74.0.1 to 40.74.127.25440.74.127.25532,766
2240.74.128.0/1740.74.128.1 to 40.74.255.25440.74.255.25532,766
2340.75.0.0/1740.75.0.1 to 40.75.127.25440.75.127.25532,766
2440.75.128.0/1740.75.128.1 to 40.75.255.25440.75.255.25532,766
2540.76.0.0/1740.76.0.1 to 40.76.127.25440.76.127.25532,766
2640.76.128.0/1740.76.128.1 to 40.76.255.25440.76.255.25532,766
2740.77.0.0/1740.77.0.1 to 40.77.127.25440.77.127.25532,766
2840.77.128.0/1740.77.128.1 to 40.77.255.25440.77.255.25532,766
2940.78.0.0/1740.78.0.1 to 40.78.127.25440.78.127.25532,766
3040.78.128.0/1740.78.128.1 to 40.78.255.25440.78.255.25532,766
3140.79.0.0/1740.79.0.1 to 40.79.127.25440.79.127.25532,766
3240.79.128.0/1740.79.128.1 to 40.79.255.25440.79.255.25532,766
3340.80.0.0/1740.80.0.1 to 40.80.127.25440.80.127.25532,766
3440.80.128.0/1740.80.128.1 to 40.80.255.25440.80.255.25532,766
3540.81.0.0/1740.81.0.1 to 40.81.127.25440.81.127.25532,766
3640.81.128.0/1740.81.128.1 to 40.81.255.25440.81.255.25532,766
3740.82.0.0/1740.82.0.1 to 40.82.127.25440.82.127.25532,766
3840.82.128.0/1740.82.128.1 to 40.82.255.25440.82.255.25532,766
3940.83.0.0/1740.83.0.1 to 40.83.127.25440.83.127.25532,766
4040.83.128.0/1740.83.128.1 to 40.83.255.25440.83.255.25532,766
4140.84.0.0/1740.84.0.1 to 40.84.127.25440.84.127.25532,766
4240.84.128.0/1740.84.128.1 to 40.84.255.25440.84.255.25532,766
4340.85.0.0/1740.85.0.1 to 40.85.127.25440.85.127.25532,766
4440.85.128.0/1740.85.128.1 to 40.85.255.25440.85.255.25532,766
4540.86.0.0/1740.86.0.1 to 40.86.127.25440.86.127.25532,766
4640.86.128.0/1740.86.128.1 to 40.86.255.25440.86.255.25532,766
4740.87.0.0/1740.87.0.1 to 40.87.127.25440.87.127.25532,766
4840.87.128.0/1740.87.128.1 to 40.87.255.25440.87.255.25532,766
4940.88.0.0/1740.88.0.1 to 40.88.127.25440.88.127.25532,766
5040.88.128.0/1740.88.128.1 to 40.88.255.25440.88.255.25532,766
5140.89.0.0/1740.89.0.1 to 40.89.127.25440.89.127.25532,766
5240.89.128.0/1740.89.128.1 to 40.89.255.25440.89.255.25532,766
5340.90.0.0/1740.90.0.1 to 40.90.127.25440.90.127.25532,766
5440.90.128.0/1740.90.128.1 to 40.90.255.25440.90.255.25532,766
5540.91.0.0/1740.91.0.1 to 40.91.127.25440.91.127.25532,766
5640.91.128.0/1740.91.128.1 to 40.91.255.25440.91.255.25532,766
5740.92.0.0/1740.92.0.1 to 40.92.127.25440.92.127.25532,766
5840.92.128.0/1740.92.128.1 to 40.92.255.25440.92.255.25532,766
5940.93.0.0/1740.93.0.1 to 40.93.127.25440.93.127.25532,766
6040.93.128.0/1740.93.128.1 to 40.93.255.25440.93.255.25532,766
6140.94.0.0/1740.94.0.1 to 40.94.127.25440.94.127.25532,766
6240.94.128.0/1740.94.128.1 to 40.94.255.25440.94.255.25532,766
6340.95.0.0/1740.95.0.1 to 40.95.127.25440.95.127.25532,766
6440.95.128.0/1740.95.128.1 to 40.95.255.25440.95.255.25532,766
6540.96.0.0/1740.96.0.1 to 40.96.127.25440.96.127.25532,766
6640.96.128.0/1740.96.128.1 to 40.96.255.25440.96.255.25532,766
6740.97.0.0/1740.97.0.1 to 40.97.127.25440.97.127.25532,766
6840.97.128.0/1740.97.128.1 to 40.97.255.25440.97.255.25532,766
6940.98.0.0/1740.98.0.1 to 40.98.127.25440.98.127.25532,766
7040.98.128.0/1740.98.128.1 to 40.98.255.25440.98.255.25532,766
7140.99.0.0/1740.99.0.1 to 40.99.127.25440.99.127.25532,766
7240.99.128.0/1740.99.128.1 to 40.99.255.25440.99.255.25532,766
7340.100.0.0/1740.100.0.1 to 40.100.127.25440.100.127.25532,766
7440.100.128.0/1740.100.128.1 to 40.100.255.25440.100.255.25532,766
7540.101.0.0/1740.101.0.1 to 40.101.127.25440.101.127.25532,766
7640.101.128.0/1740.101.128.1 to 40.101.255.25440.101.255.25532,766
7740.102.0.0/1740.102.0.1 to 40.102.127.25440.102.127.25532,766
7840.102.128.0/1740.102.128.1 to 40.102.255.25440.102.255.25532,766
7940.103.0.0/1740.103.0.1 to 40.103.127.25440.103.127.25532,766
8040.103.128.0/1740.103.128.1 to 40.103.255.25440.103.255.25532,766
8140.104.0.0/1740.104.0.1 to 40.104.127.25440.104.127.25532,766
8240.104.128.0/1740.104.128.1 to 40.104.255.25440.104.255.25532,766
8340.105.0.0/1740.105.0.1 to 40.105.127.25440.105.127.25532,766
8440.105.128.0/1740.105.128.1 to 40.105.255.25440.105.255.25532,766
8540.106.0.0/1740.106.0.1 to 40.106.127.25440.106.127.25532,766
8640.106.128.0/1740.106.128.1 to 40.106.255.25440.106.255.25532,766
8740.107.0.0/1740.107.0.1 to 40.107.127.25440.107.127.25532,766
8840.107.128.0/1740.107.128.1 to 40.107.255.25440.107.255.25532,766
8940.108.0.0/1740.108.0.1 to 40.108.127.25440.108.127.25532,766
9040.108.128.0/1740.108.128.1 to 40.108.255.25440.108.255.25532,766
9140.109.0.0/1740.109.0.1 to 40.109.127.25440.109.127.25532,766
9240.109.128.0/1740.109.128.1 to 40.109.255.25440.109.255.25532,766
9340.110.0.0/1740.110.0.1 to 40.110.127.25440.110.127.25532,766
9440.110.128.0/1740.110.128.1 to 40.110.255.25440.110.255.25532,766
9540.111.0.0/1740.111.0.1 to 40.111.127.25440.111.127.25532,766
9640.111.128.0/1740.111.128.1 to 40.111.255.25440.111.255.25532,766
9740.112.0.0/1740.112.0.1 to 40.112.127.25440.112.127.25532,766
9840.112.128.0/1740.112.128.1 to 40.112.255.25440.112.255.25532,766
9940.113.0.0/1740.113.0.1 to 40.113.127.25440.113.127.25532,766
10040.113.128.0/1740.113.128.1 to 40.113.255.25440.113.255.25532,766
10140.114.0.0/1740.114.0.1 to 40.114.127.25440.114.127.25532,766
10240.114.128.0/1740.114.128.1 to 40.114.255.25440.114.255.25532,766
10340.115.0.0/1740.115.0.1 to 40.115.127.25440.115.127.25532,766
10440.115.128.0/1740.115.128.1 to 40.115.255.25440.115.255.25532,766
10540.116.0.0/1740.116.0.1 to 40.116.127.25440.116.127.25532,766
10640.116.128.0/1740.116.128.1 to 40.116.255.25440.116.255.25532,766
10740.117.0.0/1740.117.0.1 to 40.117.127.25440.117.127.25532,766
10840.117.128.0/1740.117.128.1 to 40.117.255.25440.117.255.25532,766
10940.118.0.0/1740.118.0.1 to 40.118.127.25440.118.127.25532,766
11040.118.128.0/1740.118.128.1 to 40.118.255.25440.118.255.25532,766
11140.119.0.0/1740.119.0.1 to 40.119.127.25440.119.127.25532,766
11240.119.128.0/1740.119.128.1 to 40.119.255.25440.119.255.25532,766
11340.120.0.0/1740.120.0.1 to 40.120.127.25440.120.127.25532,766
11440.120.128.0/1740.120.128.1 to 40.120.255.25440.120.255.25532,766
11540.121.0.0/1740.121.0.1 to 40.121.127.25440.121.127.25532,766
11640.121.128.0/1740.121.128.1 to 40.121.255.25440.121.255.25532,766
11740.122.0.0/1740.122.0.1 to 40.122.127.25440.122.127.25532,766
11840.122.128.0/1740.122.128.1 to 40.122.255.25440.122.255.25532,766
11940.123.0.0/1740.123.0.1 to 40.123.127.25440.123.127.25532,766
12040.123.128.0/1740.123.128.1 to 40.123.255.25440.123.255.25532,766
12140.124.0.0/1740.124.0.1 to 40.124.127.25440.124.127.25532,766
12240.124.128.0/1740.124.128.1 to 40.124.255.25440.124.255.25532,766
12340.125.0.0/1740.125.0.1 to 40.125.127.25440.125.127.25532,766
12440.125.128.0/1740.125.128.1 to 40.125.255.25440.125.255.25532,766
12540.126.0.0/1740.126.0.1 to 40.126.127.25440.126.127.25532,766
12640.126.128.0/1740.126.128.1 to 40.126.255.25440.126.255.25532,766
12740.127.0.0/1740.127.0.1 to 40.127.127.25440.127.127.25532,766
12840.127.128.0/1740.127.128.1 to 40.127.255.25440.127.255.25532,766

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.