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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.

Network46.7.232.0/21
Usable hosts2,046
Subnet mask255.255.248.0
Addresses2,048
Network address
46.7.232.0
Broadcast address
46.7.239.255
First usable
46.7.232.1
Last usable
46.7.239.254
Usable hosts
2,046 (2,048 less the network and broadcast addresses)
Subnet mask
255.255.248.0
Wildcard mask
0.0.7.255 (Cisco ACLs, OSPF)
Prefix length
/21
Type
Public public
Old class
A (default /8)
As numbers
Hex 2E07E800 · Integer 772270080 to 772272127
Reverse DNS zones
232.7.46.in-addr.arpa
233.7.46.in-addr.arpa
234.7.46.in-addr.arpa
235.7.46.in-addr.arpa
236.7.46.in-addr.arpa
237.7.46.in-addr.arpa
238.7.46.in-addr.arpa
239.7.46.in-addr.arpa
/21 is not on a 8-bit boundary, so it takes 8 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00101110.00000111.11101000.0000000046.7.232.0
Subnet mask11111111.11111111.11111000.00000000255.255.248.0
Network00101110.00000111.11101000.0000000046.7.232.0
Broadcast00101110.00000111.11101111.1111111146.7.239.255
Split into smaller subnets/28
/22 (2)/23 (4)/24 (8)/25 (16)/26 (32)/27 (64)/28 (128)/29 (256)/30 (512)/31 (1,024)/32 (2,048)

46.7.232.0/21 makes 128 subnets of /28.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
146.7.232.0/2846.7.232.1 to 46.7.232.1446.7.232.1514
246.7.232.16/2846.7.232.17 to 46.7.232.3046.7.232.3114
346.7.232.32/2846.7.232.33 to 46.7.232.4646.7.232.4714
446.7.232.48/2846.7.232.49 to 46.7.232.6246.7.232.6314
546.7.232.64/2846.7.232.65 to 46.7.232.7846.7.232.7914
646.7.232.80/2846.7.232.81 to 46.7.232.9446.7.232.9514
746.7.232.96/2846.7.232.97 to 46.7.232.11046.7.232.11114
846.7.232.112/2846.7.232.113 to 46.7.232.12646.7.232.12714
946.7.232.128/2846.7.232.129 to 46.7.232.14246.7.232.14314
1046.7.232.144/2846.7.232.145 to 46.7.232.15846.7.232.15914
1146.7.232.160/2846.7.232.161 to 46.7.232.17446.7.232.17514
1246.7.232.176/2846.7.232.177 to 46.7.232.19046.7.232.19114
1346.7.232.192/2846.7.232.193 to 46.7.232.20646.7.232.20714
1446.7.232.208/2846.7.232.209 to 46.7.232.22246.7.232.22314
1546.7.232.224/2846.7.232.225 to 46.7.232.23846.7.232.23914
1646.7.232.240/2846.7.232.241 to 46.7.232.25446.7.232.25514
1746.7.233.0/2846.7.233.1 to 46.7.233.1446.7.233.1514
1846.7.233.16/2846.7.233.17 to 46.7.233.3046.7.233.3114
1946.7.233.32/2846.7.233.33 to 46.7.233.4646.7.233.4714
2046.7.233.48/2846.7.233.49 to 46.7.233.6246.7.233.6314
2146.7.233.64/2846.7.233.65 to 46.7.233.7846.7.233.7914
2246.7.233.80/2846.7.233.81 to 46.7.233.9446.7.233.9514
2346.7.233.96/2846.7.233.97 to 46.7.233.11046.7.233.11114
2446.7.233.112/2846.7.233.113 to 46.7.233.12646.7.233.12714
2546.7.233.128/2846.7.233.129 to 46.7.233.14246.7.233.14314
2646.7.233.144/2846.7.233.145 to 46.7.233.15846.7.233.15914
2746.7.233.160/2846.7.233.161 to 46.7.233.17446.7.233.17514
2846.7.233.176/2846.7.233.177 to 46.7.233.19046.7.233.19114
2946.7.233.192/2846.7.233.193 to 46.7.233.20646.7.233.20714
3046.7.233.208/2846.7.233.209 to 46.7.233.22246.7.233.22314
3146.7.233.224/2846.7.233.225 to 46.7.233.23846.7.233.23914
3246.7.233.240/2846.7.233.241 to 46.7.233.25446.7.233.25514
3346.7.234.0/2846.7.234.1 to 46.7.234.1446.7.234.1514
3446.7.234.16/2846.7.234.17 to 46.7.234.3046.7.234.3114
3546.7.234.32/2846.7.234.33 to 46.7.234.4646.7.234.4714
3646.7.234.48/2846.7.234.49 to 46.7.234.6246.7.234.6314
3746.7.234.64/2846.7.234.65 to 46.7.234.7846.7.234.7914
3846.7.234.80/2846.7.234.81 to 46.7.234.9446.7.234.9514
3946.7.234.96/2846.7.234.97 to 46.7.234.11046.7.234.11114
4046.7.234.112/2846.7.234.113 to 46.7.234.12646.7.234.12714
4146.7.234.128/2846.7.234.129 to 46.7.234.14246.7.234.14314
4246.7.234.144/2846.7.234.145 to 46.7.234.15846.7.234.15914
4346.7.234.160/2846.7.234.161 to 46.7.234.17446.7.234.17514
4446.7.234.176/2846.7.234.177 to 46.7.234.19046.7.234.19114
4546.7.234.192/2846.7.234.193 to 46.7.234.20646.7.234.20714
4646.7.234.208/2846.7.234.209 to 46.7.234.22246.7.234.22314
4746.7.234.224/2846.7.234.225 to 46.7.234.23846.7.234.23914
4846.7.234.240/2846.7.234.241 to 46.7.234.25446.7.234.25514
4946.7.235.0/2846.7.235.1 to 46.7.235.1446.7.235.1514
5046.7.235.16/2846.7.235.17 to 46.7.235.3046.7.235.3114
5146.7.235.32/2846.7.235.33 to 46.7.235.4646.7.235.4714
5246.7.235.48/2846.7.235.49 to 46.7.235.6246.7.235.6314
5346.7.235.64/2846.7.235.65 to 46.7.235.7846.7.235.7914
5446.7.235.80/2846.7.235.81 to 46.7.235.9446.7.235.9514
5546.7.235.96/2846.7.235.97 to 46.7.235.11046.7.235.11114
5646.7.235.112/2846.7.235.113 to 46.7.235.12646.7.235.12714
5746.7.235.128/2846.7.235.129 to 46.7.235.14246.7.235.14314
5846.7.235.144/2846.7.235.145 to 46.7.235.15846.7.235.15914
5946.7.235.160/2846.7.235.161 to 46.7.235.17446.7.235.17514
6046.7.235.176/2846.7.235.177 to 46.7.235.19046.7.235.19114
6146.7.235.192/2846.7.235.193 to 46.7.235.20646.7.235.20714
6246.7.235.208/2846.7.235.209 to 46.7.235.22246.7.235.22314
6346.7.235.224/2846.7.235.225 to 46.7.235.23846.7.235.23914
6446.7.235.240/2846.7.235.241 to 46.7.235.25446.7.235.25514
6546.7.236.0/2846.7.236.1 to 46.7.236.1446.7.236.1514
6646.7.236.16/2846.7.236.17 to 46.7.236.3046.7.236.3114
6746.7.236.32/2846.7.236.33 to 46.7.236.4646.7.236.4714
6846.7.236.48/2846.7.236.49 to 46.7.236.6246.7.236.6314
6946.7.236.64/2846.7.236.65 to 46.7.236.7846.7.236.7914
7046.7.236.80/2846.7.236.81 to 46.7.236.9446.7.236.9514
7146.7.236.96/2846.7.236.97 to 46.7.236.11046.7.236.11114
7246.7.236.112/2846.7.236.113 to 46.7.236.12646.7.236.12714
7346.7.236.128/2846.7.236.129 to 46.7.236.14246.7.236.14314
7446.7.236.144/2846.7.236.145 to 46.7.236.15846.7.236.15914
7546.7.236.160/2846.7.236.161 to 46.7.236.17446.7.236.17514
7646.7.236.176/2846.7.236.177 to 46.7.236.19046.7.236.19114
7746.7.236.192/2846.7.236.193 to 46.7.236.20646.7.236.20714
7846.7.236.208/2846.7.236.209 to 46.7.236.22246.7.236.22314
7946.7.236.224/2846.7.236.225 to 46.7.236.23846.7.236.23914
8046.7.236.240/2846.7.236.241 to 46.7.236.25446.7.236.25514
8146.7.237.0/2846.7.237.1 to 46.7.237.1446.7.237.1514
8246.7.237.16/2846.7.237.17 to 46.7.237.3046.7.237.3114
8346.7.237.32/2846.7.237.33 to 46.7.237.4646.7.237.4714
8446.7.237.48/2846.7.237.49 to 46.7.237.6246.7.237.6314
8546.7.237.64/2846.7.237.65 to 46.7.237.7846.7.237.7914
8646.7.237.80/2846.7.237.81 to 46.7.237.9446.7.237.9514
8746.7.237.96/2846.7.237.97 to 46.7.237.11046.7.237.11114
8846.7.237.112/2846.7.237.113 to 46.7.237.12646.7.237.12714
8946.7.237.128/2846.7.237.129 to 46.7.237.14246.7.237.14314
9046.7.237.144/2846.7.237.145 to 46.7.237.15846.7.237.15914
9146.7.237.160/2846.7.237.161 to 46.7.237.17446.7.237.17514
9246.7.237.176/2846.7.237.177 to 46.7.237.19046.7.237.19114
9346.7.237.192/2846.7.237.193 to 46.7.237.20646.7.237.20714
9446.7.237.208/2846.7.237.209 to 46.7.237.22246.7.237.22314
9546.7.237.224/2846.7.237.225 to 46.7.237.23846.7.237.23914
9646.7.237.240/2846.7.237.241 to 46.7.237.25446.7.237.25514
9746.7.238.0/2846.7.238.1 to 46.7.238.1446.7.238.1514
9846.7.238.16/2846.7.238.17 to 46.7.238.3046.7.238.3114
9946.7.238.32/2846.7.238.33 to 46.7.238.4646.7.238.4714
10046.7.238.48/2846.7.238.49 to 46.7.238.6246.7.238.6314
10146.7.238.64/2846.7.238.65 to 46.7.238.7846.7.238.7914
10246.7.238.80/2846.7.238.81 to 46.7.238.9446.7.238.9514
10346.7.238.96/2846.7.238.97 to 46.7.238.11046.7.238.11114
10446.7.238.112/2846.7.238.113 to 46.7.238.12646.7.238.12714
10546.7.238.128/2846.7.238.129 to 46.7.238.14246.7.238.14314
10646.7.238.144/2846.7.238.145 to 46.7.238.15846.7.238.15914
10746.7.238.160/2846.7.238.161 to 46.7.238.17446.7.238.17514
10846.7.238.176/2846.7.238.177 to 46.7.238.19046.7.238.19114
10946.7.238.192/2846.7.238.193 to 46.7.238.20646.7.238.20714
11046.7.238.208/2846.7.238.209 to 46.7.238.22246.7.238.22314
11146.7.238.224/2846.7.238.225 to 46.7.238.23846.7.238.23914
11246.7.238.240/2846.7.238.241 to 46.7.238.25446.7.238.25514
11346.7.239.0/2846.7.239.1 to 46.7.239.1446.7.239.1514
11446.7.239.16/2846.7.239.17 to 46.7.239.3046.7.239.3114
11546.7.239.32/2846.7.239.33 to 46.7.239.4646.7.239.4714
11646.7.239.48/2846.7.239.49 to 46.7.239.6246.7.239.6314
11746.7.239.64/2846.7.239.65 to 46.7.239.7846.7.239.7914
11846.7.239.80/2846.7.239.81 to 46.7.239.9446.7.239.9514
11946.7.239.96/2846.7.239.97 to 46.7.239.11046.7.239.11114
12046.7.239.112/2846.7.239.113 to 46.7.239.12646.7.239.12714
12146.7.239.128/2846.7.239.129 to 46.7.239.14246.7.239.14314
12246.7.239.144/2846.7.239.145 to 46.7.239.15846.7.239.15914
12346.7.239.160/2846.7.239.161 to 46.7.239.17446.7.239.17514
12446.7.239.176/2846.7.239.177 to 46.7.239.19046.7.239.19114
12546.7.239.192/2846.7.239.193 to 46.7.239.20646.7.239.20714
12646.7.239.208/2846.7.239.209 to 46.7.239.22246.7.239.22314
12746.7.239.224/2846.7.239.225 to 46.7.239.23846.7.239.23914
12846.7.239.240/2846.7.239.241 to 46.7.239.25446.7.239.25514

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.