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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.

Network40.3.78.128/26
Usable hosts62
Subnet mask255.255.255.192
Addresses64
Network address
40.3.78.128
Broadcast address
40.3.78.191
First usable
40.3.78.129
Last usable
40.3.78.190
Usable hosts
62 (64 less the network and broadcast addresses)
Subnet mask
255.255.255.192
Wildcard mask
0.0.0.63 (Cisco ACLs, OSPF)
Prefix length
/26
Type
Public public
Old class
A (default /8)
As numbers
Hex 28034E80 · Integer 671305344 to 671305407
Reverse DNS zone
78.3.40.in-addr.arpa
Smaller than a /24: the provider delegates it inside the /24 zone (RFC 2317), or sets each PTR record for you.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00101000.00000011.01001110.1000000040.3.78.128
Subnet mask11111111.11111111.11111111.11000000255.255.255.192
Network00101000.00000011.01001110.1000000040.3.78.128
Broadcast00101000.00000011.01001110.1011111140.3.78.191
Split into smaller subnets/32
/27 (2)/28 (4)/29 (8)/30 (16)/31 (32)/32 (64)

40.3.78.128/26 makes 64 subnets of /32.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
140.3.78.128/3240.3.78.128 to 40.3.78.128—1
240.3.78.129/3240.3.78.129 to 40.3.78.129—1
340.3.78.130/3240.3.78.130 to 40.3.78.130—1
440.3.78.131/3240.3.78.131 to 40.3.78.131—1
540.3.78.132/3240.3.78.132 to 40.3.78.132—1
640.3.78.133/3240.3.78.133 to 40.3.78.133—1
740.3.78.134/3240.3.78.134 to 40.3.78.134—1
840.3.78.135/3240.3.78.135 to 40.3.78.135—1
940.3.78.136/3240.3.78.136 to 40.3.78.136—1
1040.3.78.137/3240.3.78.137 to 40.3.78.137—1
1140.3.78.138/3240.3.78.138 to 40.3.78.138—1
1240.3.78.139/3240.3.78.139 to 40.3.78.139—1
1340.3.78.140/3240.3.78.140 to 40.3.78.140—1
1440.3.78.141/3240.3.78.141 to 40.3.78.141—1
1540.3.78.142/3240.3.78.142 to 40.3.78.142—1
1640.3.78.143/3240.3.78.143 to 40.3.78.143—1
1740.3.78.144/3240.3.78.144 to 40.3.78.144—1
1840.3.78.145/3240.3.78.145 to 40.3.78.145—1
1940.3.78.146/3240.3.78.146 to 40.3.78.146—1
2040.3.78.147/3240.3.78.147 to 40.3.78.147—1
2140.3.78.148/3240.3.78.148 to 40.3.78.148—1
2240.3.78.149/3240.3.78.149 to 40.3.78.149—1
2340.3.78.150/3240.3.78.150 to 40.3.78.150—1
2440.3.78.151/3240.3.78.151 to 40.3.78.151—1
2540.3.78.152/3240.3.78.152 to 40.3.78.152—1
2640.3.78.153/3240.3.78.153 to 40.3.78.153—1
2740.3.78.154/3240.3.78.154 to 40.3.78.154—1
2840.3.78.155/3240.3.78.155 to 40.3.78.155—1
2940.3.78.156/3240.3.78.156 to 40.3.78.156—1
3040.3.78.157/3240.3.78.157 to 40.3.78.157—1
3140.3.78.158/3240.3.78.158 to 40.3.78.158—1
3240.3.78.159/3240.3.78.159 to 40.3.78.159—1
3340.3.78.160/3240.3.78.160 to 40.3.78.160—1
3440.3.78.161/3240.3.78.161 to 40.3.78.161—1
3540.3.78.162/3240.3.78.162 to 40.3.78.162—1
3640.3.78.163/3240.3.78.163 to 40.3.78.163—1
3740.3.78.164/3240.3.78.164 to 40.3.78.164—1
3840.3.78.165/3240.3.78.165 to 40.3.78.165—1
3940.3.78.166/3240.3.78.166 to 40.3.78.166—1
4040.3.78.167/3240.3.78.167 to 40.3.78.167—1
4140.3.78.168/3240.3.78.168 to 40.3.78.168—1
4240.3.78.169/3240.3.78.169 to 40.3.78.169—1
4340.3.78.170/3240.3.78.170 to 40.3.78.170—1
4440.3.78.171/3240.3.78.171 to 40.3.78.171—1
4540.3.78.172/3240.3.78.172 to 40.3.78.172—1
4640.3.78.173/3240.3.78.173 to 40.3.78.173—1
4740.3.78.174/3240.3.78.174 to 40.3.78.174—1
4840.3.78.175/3240.3.78.175 to 40.3.78.175—1
4940.3.78.176/3240.3.78.176 to 40.3.78.176—1
5040.3.78.177/3240.3.78.177 to 40.3.78.177—1
5140.3.78.178/3240.3.78.178 to 40.3.78.178—1
5240.3.78.179/3240.3.78.179 to 40.3.78.179—1
5340.3.78.180/3240.3.78.180 to 40.3.78.180—1
5440.3.78.181/3240.3.78.181 to 40.3.78.181—1
5540.3.78.182/3240.3.78.182 to 40.3.78.182—1
5640.3.78.183/3240.3.78.183 to 40.3.78.183—1
5740.3.78.184/3240.3.78.184 to 40.3.78.184—1
5840.3.78.185/3240.3.78.185 to 40.3.78.185—1
5940.3.78.186/3240.3.78.186 to 40.3.78.186—1
6040.3.78.187/3240.3.78.187 to 40.3.78.187—1
6140.3.78.188/3240.3.78.188 to 40.3.78.188—1
6240.3.78.189/3240.3.78.189 to 40.3.78.189—1
6340.3.78.190/3240.3.78.190 to 40.3.78.190—1
6440.3.78.191/3240.3.78.191 to 40.3.78.191—1

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.