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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.

Network70.32.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
70.32.0.0
Broadcast address
70.47.255.255
First usable
70.32.0.1
Last usable
70.47.255.254
Usable hosts
1,048,574 (1,048,576 less the network and broadcast addresses)
Subnet mask
255.240.0.0
Wildcard mask
0.15.255.255 (Cisco ACLs, OSPF)
Prefix length
/12
Type
Public public
Old class
A (default /8)
As numbers
Hex 46200000 · Integer 1176502272 to 1177550847
Reverse DNS zones
32.70.in-addr.arpa
33.70.in-addr.arpa
34.70.in-addr.arpa
35.70.in-addr.arpa
36.70.in-addr.arpa
37.70.in-addr.arpa
38.70.in-addr.arpa
39.70.in-addr.arpa
40.70.in-addr.arpa
41.70.in-addr.arpa
42.70.in-addr.arpa
43.70.in-addr.arpa
44.70.in-addr.arpa
45.70.in-addr.arpa
46.70.in-addr.arpa
47.70.in-addr.arpa
/12 is not on a 8-bit boundary, so it takes 16 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01000110.00100000.00000000.0000000070.32.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network01000110.00100000.00000000.0000000070.32.0.0
Broadcast01000110.00101111.11111111.1111111170.47.255.255
Split into smaller subnets/19
/13 (2)/14 (4)/15 (8)/16 (16)/17 (32)/18 (64)/19 (128)/20 (256)/21 (512)/22 (1,024)/23 (2,048)/24 (4,096)

70.32.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
170.32.0.0/1970.32.0.1 to 70.32.31.25470.32.31.2558,190
270.32.32.0/1970.32.32.1 to 70.32.63.25470.32.63.2558,190
370.32.64.0/1970.32.64.1 to 70.32.95.25470.32.95.2558,190
470.32.96.0/1970.32.96.1 to 70.32.127.25470.32.127.2558,190
570.32.128.0/1970.32.128.1 to 70.32.159.25470.32.159.2558,190
670.32.160.0/1970.32.160.1 to 70.32.191.25470.32.191.2558,190
770.32.192.0/1970.32.192.1 to 70.32.223.25470.32.223.2558,190
870.32.224.0/1970.32.224.1 to 70.32.255.25470.32.255.2558,190
970.33.0.0/1970.33.0.1 to 70.33.31.25470.33.31.2558,190
1070.33.32.0/1970.33.32.1 to 70.33.63.25470.33.63.2558,190
1170.33.64.0/1970.33.64.1 to 70.33.95.25470.33.95.2558,190
1270.33.96.0/1970.33.96.1 to 70.33.127.25470.33.127.2558,190
1370.33.128.0/1970.33.128.1 to 70.33.159.25470.33.159.2558,190
1470.33.160.0/1970.33.160.1 to 70.33.191.25470.33.191.2558,190
1570.33.192.0/1970.33.192.1 to 70.33.223.25470.33.223.2558,190
1670.33.224.0/1970.33.224.1 to 70.33.255.25470.33.255.2558,190
1770.34.0.0/1970.34.0.1 to 70.34.31.25470.34.31.2558,190
1870.34.32.0/1970.34.32.1 to 70.34.63.25470.34.63.2558,190
1970.34.64.0/1970.34.64.1 to 70.34.95.25470.34.95.2558,190
2070.34.96.0/1970.34.96.1 to 70.34.127.25470.34.127.2558,190
2170.34.128.0/1970.34.128.1 to 70.34.159.25470.34.159.2558,190
2270.34.160.0/1970.34.160.1 to 70.34.191.25470.34.191.2558,190
2370.34.192.0/1970.34.192.1 to 70.34.223.25470.34.223.2558,190
2470.34.224.0/1970.34.224.1 to 70.34.255.25470.34.255.2558,190
2570.35.0.0/1970.35.0.1 to 70.35.31.25470.35.31.2558,190
2670.35.32.0/1970.35.32.1 to 70.35.63.25470.35.63.2558,190
2770.35.64.0/1970.35.64.1 to 70.35.95.25470.35.95.2558,190
2870.35.96.0/1970.35.96.1 to 70.35.127.25470.35.127.2558,190
2970.35.128.0/1970.35.128.1 to 70.35.159.25470.35.159.2558,190
3070.35.160.0/1970.35.160.1 to 70.35.191.25470.35.191.2558,190
3170.35.192.0/1970.35.192.1 to 70.35.223.25470.35.223.2558,190
3270.35.224.0/1970.35.224.1 to 70.35.255.25470.35.255.2558,190
3370.36.0.0/1970.36.0.1 to 70.36.31.25470.36.31.2558,190
3470.36.32.0/1970.36.32.1 to 70.36.63.25470.36.63.2558,190
3570.36.64.0/1970.36.64.1 to 70.36.95.25470.36.95.2558,190
3670.36.96.0/1970.36.96.1 to 70.36.127.25470.36.127.2558,190
3770.36.128.0/1970.36.128.1 to 70.36.159.25470.36.159.2558,190
3870.36.160.0/1970.36.160.1 to 70.36.191.25470.36.191.2558,190
3970.36.192.0/1970.36.192.1 to 70.36.223.25470.36.223.2558,190
4070.36.224.0/1970.36.224.1 to 70.36.255.25470.36.255.2558,190
4170.37.0.0/1970.37.0.1 to 70.37.31.25470.37.31.2558,190
4270.37.32.0/1970.37.32.1 to 70.37.63.25470.37.63.2558,190
4370.37.64.0/1970.37.64.1 to 70.37.95.25470.37.95.2558,190
4470.37.96.0/1970.37.96.1 to 70.37.127.25470.37.127.2558,190
4570.37.128.0/1970.37.128.1 to 70.37.159.25470.37.159.2558,190
4670.37.160.0/1970.37.160.1 to 70.37.191.25470.37.191.2558,190
4770.37.192.0/1970.37.192.1 to 70.37.223.25470.37.223.2558,190
4870.37.224.0/1970.37.224.1 to 70.37.255.25470.37.255.2558,190
4970.38.0.0/1970.38.0.1 to 70.38.31.25470.38.31.2558,190
5070.38.32.0/1970.38.32.1 to 70.38.63.25470.38.63.2558,190
5170.38.64.0/1970.38.64.1 to 70.38.95.25470.38.95.2558,190
5270.38.96.0/1970.38.96.1 to 70.38.127.25470.38.127.2558,190
5370.38.128.0/1970.38.128.1 to 70.38.159.25470.38.159.2558,190
5470.38.160.0/1970.38.160.1 to 70.38.191.25470.38.191.2558,190
5570.38.192.0/1970.38.192.1 to 70.38.223.25470.38.223.2558,190
5670.38.224.0/1970.38.224.1 to 70.38.255.25470.38.255.2558,190
5770.39.0.0/1970.39.0.1 to 70.39.31.25470.39.31.2558,190
5870.39.32.0/1970.39.32.1 to 70.39.63.25470.39.63.2558,190
5970.39.64.0/1970.39.64.1 to 70.39.95.25470.39.95.2558,190
6070.39.96.0/1970.39.96.1 to 70.39.127.25470.39.127.2558,190
6170.39.128.0/1970.39.128.1 to 70.39.159.25470.39.159.2558,190
6270.39.160.0/1970.39.160.1 to 70.39.191.25470.39.191.2558,190
6370.39.192.0/1970.39.192.1 to 70.39.223.25470.39.223.2558,190
6470.39.224.0/1970.39.224.1 to 70.39.255.25470.39.255.2558,190
6570.40.0.0/1970.40.0.1 to 70.40.31.25470.40.31.2558,190
6670.40.32.0/1970.40.32.1 to 70.40.63.25470.40.63.2558,190
6770.40.64.0/1970.40.64.1 to 70.40.95.25470.40.95.2558,190
6870.40.96.0/1970.40.96.1 to 70.40.127.25470.40.127.2558,190
6970.40.128.0/1970.40.128.1 to 70.40.159.25470.40.159.2558,190
7070.40.160.0/1970.40.160.1 to 70.40.191.25470.40.191.2558,190
7170.40.192.0/1970.40.192.1 to 70.40.223.25470.40.223.2558,190
7270.40.224.0/1970.40.224.1 to 70.40.255.25470.40.255.2558,190
7370.41.0.0/1970.41.0.1 to 70.41.31.25470.41.31.2558,190
7470.41.32.0/1970.41.32.1 to 70.41.63.25470.41.63.2558,190
7570.41.64.0/1970.41.64.1 to 70.41.95.25470.41.95.2558,190
7670.41.96.0/1970.41.96.1 to 70.41.127.25470.41.127.2558,190
7770.41.128.0/1970.41.128.1 to 70.41.159.25470.41.159.2558,190
7870.41.160.0/1970.41.160.1 to 70.41.191.25470.41.191.2558,190
7970.41.192.0/1970.41.192.1 to 70.41.223.25470.41.223.2558,190
8070.41.224.0/1970.41.224.1 to 70.41.255.25470.41.255.2558,190
8170.42.0.0/1970.42.0.1 to 70.42.31.25470.42.31.2558,190
8270.42.32.0/1970.42.32.1 to 70.42.63.25470.42.63.2558,190
8370.42.64.0/1970.42.64.1 to 70.42.95.25470.42.95.2558,190
8470.42.96.0/1970.42.96.1 to 70.42.127.25470.42.127.2558,190
8570.42.128.0/1970.42.128.1 to 70.42.159.25470.42.159.2558,190
8670.42.160.0/1970.42.160.1 to 70.42.191.25470.42.191.2558,190
8770.42.192.0/1970.42.192.1 to 70.42.223.25470.42.223.2558,190
8870.42.224.0/1970.42.224.1 to 70.42.255.25470.42.255.2558,190
8970.43.0.0/1970.43.0.1 to 70.43.31.25470.43.31.2558,190
9070.43.32.0/1970.43.32.1 to 70.43.63.25470.43.63.2558,190
9170.43.64.0/1970.43.64.1 to 70.43.95.25470.43.95.2558,190
9270.43.96.0/1970.43.96.1 to 70.43.127.25470.43.127.2558,190
9370.43.128.0/1970.43.128.1 to 70.43.159.25470.43.159.2558,190
9470.43.160.0/1970.43.160.1 to 70.43.191.25470.43.191.2558,190
9570.43.192.0/1970.43.192.1 to 70.43.223.25470.43.223.2558,190
9670.43.224.0/1970.43.224.1 to 70.43.255.25470.43.255.2558,190
9770.44.0.0/1970.44.0.1 to 70.44.31.25470.44.31.2558,190
9870.44.32.0/1970.44.32.1 to 70.44.63.25470.44.63.2558,190
9970.44.64.0/1970.44.64.1 to 70.44.95.25470.44.95.2558,190
10070.44.96.0/1970.44.96.1 to 70.44.127.25470.44.127.2558,190
10170.44.128.0/1970.44.128.1 to 70.44.159.25470.44.159.2558,190
10270.44.160.0/1970.44.160.1 to 70.44.191.25470.44.191.2558,190
10370.44.192.0/1970.44.192.1 to 70.44.223.25470.44.223.2558,190
10470.44.224.0/1970.44.224.1 to 70.44.255.25470.44.255.2558,190
10570.45.0.0/1970.45.0.1 to 70.45.31.25470.45.31.2558,190
10670.45.32.0/1970.45.32.1 to 70.45.63.25470.45.63.2558,190
10770.45.64.0/1970.45.64.1 to 70.45.95.25470.45.95.2558,190
10870.45.96.0/1970.45.96.1 to 70.45.127.25470.45.127.2558,190
10970.45.128.0/1970.45.128.1 to 70.45.159.25470.45.159.2558,190
11070.45.160.0/1970.45.160.1 to 70.45.191.25470.45.191.2558,190
11170.45.192.0/1970.45.192.1 to 70.45.223.25470.45.223.2558,190
11270.45.224.0/1970.45.224.1 to 70.45.255.25470.45.255.2558,190
11370.46.0.0/1970.46.0.1 to 70.46.31.25470.46.31.2558,190
11470.46.32.0/1970.46.32.1 to 70.46.63.25470.46.63.2558,190
11570.46.64.0/1970.46.64.1 to 70.46.95.25470.46.95.2558,190
11670.46.96.0/1970.46.96.1 to 70.46.127.25470.46.127.2558,190
11770.46.128.0/1970.46.128.1 to 70.46.159.25470.46.159.2558,190
11870.46.160.0/1970.46.160.1 to 70.46.191.25470.46.191.2558,190
11970.46.192.0/1970.46.192.1 to 70.46.223.25470.46.223.2558,190
12070.46.224.0/1970.46.224.1 to 70.46.255.25470.46.255.2558,190
12170.47.0.0/1970.47.0.1 to 70.47.31.25470.47.31.2558,190
12270.47.32.0/1970.47.32.1 to 70.47.63.25470.47.63.2558,190
12370.47.64.0/1970.47.64.1 to 70.47.95.25470.47.95.2558,190
12470.47.96.0/1970.47.96.1 to 70.47.127.25470.47.127.2558,190
12570.47.128.0/1970.47.128.1 to 70.47.159.25470.47.159.2558,190
12670.47.160.0/1970.47.160.1 to 70.47.191.25470.47.191.2558,190
12770.47.192.0/1970.47.192.1 to 70.47.223.25470.47.223.2558,190
12870.47.224.0/1970.47.224.1 to 70.47.255.25470.47.255.2558,190

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.