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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.

Network74.16.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
74.16.0.0
Broadcast address
74.31.255.255
First usable
74.16.0.1
Last usable
74.31.255.254
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 4A100000 · Integer 1242562560 to 1243611135
Reverse DNS zones
16.74.in-addr.arpa
17.74.in-addr.arpa
18.74.in-addr.arpa
19.74.in-addr.arpa
20.74.in-addr.arpa
21.74.in-addr.arpa
22.74.in-addr.arpa
23.74.in-addr.arpa
24.74.in-addr.arpa
25.74.in-addr.arpa
26.74.in-addr.arpa
27.74.in-addr.arpa
28.74.in-addr.arpa
29.74.in-addr.arpa
30.74.in-addr.arpa
31.74.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
Address01001010.00010000.00000000.0000000074.16.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network01001010.00010000.00000000.0000000074.16.0.0
Broadcast01001010.00011111.11111111.1111111174.31.255.255
Split into smaller subnets/18
/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)

74.16.0.0/12 makes 64 subnets of /18.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
174.16.0.0/1874.16.0.1 to 74.16.63.25474.16.63.25516,382
274.16.64.0/1874.16.64.1 to 74.16.127.25474.16.127.25516,382
374.16.128.0/1874.16.128.1 to 74.16.191.25474.16.191.25516,382
474.16.192.0/1874.16.192.1 to 74.16.255.25474.16.255.25516,382
574.17.0.0/1874.17.0.1 to 74.17.63.25474.17.63.25516,382
674.17.64.0/1874.17.64.1 to 74.17.127.25474.17.127.25516,382
774.17.128.0/1874.17.128.1 to 74.17.191.25474.17.191.25516,382
874.17.192.0/1874.17.192.1 to 74.17.255.25474.17.255.25516,382
974.18.0.0/1874.18.0.1 to 74.18.63.25474.18.63.25516,382
1074.18.64.0/1874.18.64.1 to 74.18.127.25474.18.127.25516,382
1174.18.128.0/1874.18.128.1 to 74.18.191.25474.18.191.25516,382
1274.18.192.0/1874.18.192.1 to 74.18.255.25474.18.255.25516,382
1374.19.0.0/1874.19.0.1 to 74.19.63.25474.19.63.25516,382
1474.19.64.0/1874.19.64.1 to 74.19.127.25474.19.127.25516,382
1574.19.128.0/1874.19.128.1 to 74.19.191.25474.19.191.25516,382
1674.19.192.0/1874.19.192.1 to 74.19.255.25474.19.255.25516,382
1774.20.0.0/1874.20.0.1 to 74.20.63.25474.20.63.25516,382
1874.20.64.0/1874.20.64.1 to 74.20.127.25474.20.127.25516,382
1974.20.128.0/1874.20.128.1 to 74.20.191.25474.20.191.25516,382
2074.20.192.0/1874.20.192.1 to 74.20.255.25474.20.255.25516,382
2174.21.0.0/1874.21.0.1 to 74.21.63.25474.21.63.25516,382
2274.21.64.0/1874.21.64.1 to 74.21.127.25474.21.127.25516,382
2374.21.128.0/1874.21.128.1 to 74.21.191.25474.21.191.25516,382
2474.21.192.0/1874.21.192.1 to 74.21.255.25474.21.255.25516,382
2574.22.0.0/1874.22.0.1 to 74.22.63.25474.22.63.25516,382
2674.22.64.0/1874.22.64.1 to 74.22.127.25474.22.127.25516,382
2774.22.128.0/1874.22.128.1 to 74.22.191.25474.22.191.25516,382
2874.22.192.0/1874.22.192.1 to 74.22.255.25474.22.255.25516,382
2974.23.0.0/1874.23.0.1 to 74.23.63.25474.23.63.25516,382
3074.23.64.0/1874.23.64.1 to 74.23.127.25474.23.127.25516,382
3174.23.128.0/1874.23.128.1 to 74.23.191.25474.23.191.25516,382
3274.23.192.0/1874.23.192.1 to 74.23.255.25474.23.255.25516,382
3374.24.0.0/1874.24.0.1 to 74.24.63.25474.24.63.25516,382
3474.24.64.0/1874.24.64.1 to 74.24.127.25474.24.127.25516,382
3574.24.128.0/1874.24.128.1 to 74.24.191.25474.24.191.25516,382
3674.24.192.0/1874.24.192.1 to 74.24.255.25474.24.255.25516,382
3774.25.0.0/1874.25.0.1 to 74.25.63.25474.25.63.25516,382
3874.25.64.0/1874.25.64.1 to 74.25.127.25474.25.127.25516,382
3974.25.128.0/1874.25.128.1 to 74.25.191.25474.25.191.25516,382
4074.25.192.0/1874.25.192.1 to 74.25.255.25474.25.255.25516,382
4174.26.0.0/1874.26.0.1 to 74.26.63.25474.26.63.25516,382
4274.26.64.0/1874.26.64.1 to 74.26.127.25474.26.127.25516,382
4374.26.128.0/1874.26.128.1 to 74.26.191.25474.26.191.25516,382
4474.26.192.0/1874.26.192.1 to 74.26.255.25474.26.255.25516,382
4574.27.0.0/1874.27.0.1 to 74.27.63.25474.27.63.25516,382
4674.27.64.0/1874.27.64.1 to 74.27.127.25474.27.127.25516,382
4774.27.128.0/1874.27.128.1 to 74.27.191.25474.27.191.25516,382
4874.27.192.0/1874.27.192.1 to 74.27.255.25474.27.255.25516,382
4974.28.0.0/1874.28.0.1 to 74.28.63.25474.28.63.25516,382
5074.28.64.0/1874.28.64.1 to 74.28.127.25474.28.127.25516,382
5174.28.128.0/1874.28.128.1 to 74.28.191.25474.28.191.25516,382
5274.28.192.0/1874.28.192.1 to 74.28.255.25474.28.255.25516,382
5374.29.0.0/1874.29.0.1 to 74.29.63.25474.29.63.25516,382
5474.29.64.0/1874.29.64.1 to 74.29.127.25474.29.127.25516,382
5574.29.128.0/1874.29.128.1 to 74.29.191.25474.29.191.25516,382
5674.29.192.0/1874.29.192.1 to 74.29.255.25474.29.255.25516,382
5774.30.0.0/1874.30.0.1 to 74.30.63.25474.30.63.25516,382
5874.30.64.0/1874.30.64.1 to 74.30.127.25474.30.127.25516,382
5974.30.128.0/1874.30.128.1 to 74.30.191.25474.30.191.25516,382
6074.30.192.0/1874.30.192.1 to 74.30.255.25474.30.255.25516,382
6174.31.0.0/1874.31.0.1 to 74.31.63.25474.31.63.25516,382
6274.31.64.0/1874.31.64.1 to 74.31.127.25474.31.127.25516,382
6374.31.128.0/1874.31.128.1 to 74.31.191.25474.31.191.25516,382
6474.31.192.0/1874.31.192.1 to 74.31.255.25474.31.255.25516,382

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.