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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.

Network97.4.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
97.4.0.0
Broadcast address
97.5.255.255
First usable
97.4.0.1
Last usable
97.5.255.254
Usable hosts
131,070 (131,072 less the network and broadcast addresses)
Subnet mask
255.254.0.0
Wildcard mask
0.1.255.255 (Cisco ACLs, OSPF)
Prefix length
/15
Type
Public public
Old class
A (default /8)
As numbers
Hex 61040000 · Integer 1627652096 to 1627783167
Reverse DNS zones
4.97.in-addr.arpa
5.97.in-addr.arpa
/15 is not on a 8-bit boundary, so it takes 2 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address01100001.00000100.00000000.0000000097.4.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network01100001.00000100.00000000.0000000097.4.0.0
Broadcast01100001.00000101.11111111.1111111197.5.255.255
Split into smaller subnets/21
/16 (2)/17 (4)/18 (8)/19 (16)/20 (32)/21 (64)/22 (128)/23 (256)/24 (512)/25 (1,024)/26 (2,048)/27 (4,096)

97.4.0.0/15 makes 64 subnets of /21.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
197.4.0.0/2197.4.0.1 to 97.4.7.25497.4.7.2552,046
297.4.8.0/2197.4.8.1 to 97.4.15.25497.4.15.2552,046
397.4.16.0/2197.4.16.1 to 97.4.23.25497.4.23.2552,046
497.4.24.0/2197.4.24.1 to 97.4.31.25497.4.31.2552,046
597.4.32.0/2197.4.32.1 to 97.4.39.25497.4.39.2552,046
697.4.40.0/2197.4.40.1 to 97.4.47.25497.4.47.2552,046
797.4.48.0/2197.4.48.1 to 97.4.55.25497.4.55.2552,046
897.4.56.0/2197.4.56.1 to 97.4.63.25497.4.63.2552,046
997.4.64.0/2197.4.64.1 to 97.4.71.25497.4.71.2552,046
1097.4.72.0/2197.4.72.1 to 97.4.79.25497.4.79.2552,046
1197.4.80.0/2197.4.80.1 to 97.4.87.25497.4.87.2552,046
1297.4.88.0/2197.4.88.1 to 97.4.95.25497.4.95.2552,046
1397.4.96.0/2197.4.96.1 to 97.4.103.25497.4.103.2552,046
1497.4.104.0/2197.4.104.1 to 97.4.111.25497.4.111.2552,046
1597.4.112.0/2197.4.112.1 to 97.4.119.25497.4.119.2552,046
1697.4.120.0/2197.4.120.1 to 97.4.127.25497.4.127.2552,046
1797.4.128.0/2197.4.128.1 to 97.4.135.25497.4.135.2552,046
1897.4.136.0/2197.4.136.1 to 97.4.143.25497.4.143.2552,046
1997.4.144.0/2197.4.144.1 to 97.4.151.25497.4.151.2552,046
2097.4.152.0/2197.4.152.1 to 97.4.159.25497.4.159.2552,046
2197.4.160.0/2197.4.160.1 to 97.4.167.25497.4.167.2552,046
2297.4.168.0/2197.4.168.1 to 97.4.175.25497.4.175.2552,046
2397.4.176.0/2197.4.176.1 to 97.4.183.25497.4.183.2552,046
2497.4.184.0/2197.4.184.1 to 97.4.191.25497.4.191.2552,046
2597.4.192.0/2197.4.192.1 to 97.4.199.25497.4.199.2552,046
2697.4.200.0/2197.4.200.1 to 97.4.207.25497.4.207.2552,046
2797.4.208.0/2197.4.208.1 to 97.4.215.25497.4.215.2552,046
2897.4.216.0/2197.4.216.1 to 97.4.223.25497.4.223.2552,046
2997.4.224.0/2197.4.224.1 to 97.4.231.25497.4.231.2552,046
3097.4.232.0/2197.4.232.1 to 97.4.239.25497.4.239.2552,046
3197.4.240.0/2197.4.240.1 to 97.4.247.25497.4.247.2552,046
3297.4.248.0/2197.4.248.1 to 97.4.255.25497.4.255.2552,046
3397.5.0.0/2197.5.0.1 to 97.5.7.25497.5.7.2552,046
3497.5.8.0/2197.5.8.1 to 97.5.15.25497.5.15.2552,046
3597.5.16.0/2197.5.16.1 to 97.5.23.25497.5.23.2552,046
3697.5.24.0/2197.5.24.1 to 97.5.31.25497.5.31.2552,046
3797.5.32.0/2197.5.32.1 to 97.5.39.25497.5.39.2552,046
3897.5.40.0/2197.5.40.1 to 97.5.47.25497.5.47.2552,046
3997.5.48.0/2197.5.48.1 to 97.5.55.25497.5.55.2552,046
4097.5.56.0/2197.5.56.1 to 97.5.63.25497.5.63.2552,046
4197.5.64.0/2197.5.64.1 to 97.5.71.25497.5.71.2552,046
4297.5.72.0/2197.5.72.1 to 97.5.79.25497.5.79.2552,046
4397.5.80.0/2197.5.80.1 to 97.5.87.25497.5.87.2552,046
4497.5.88.0/2197.5.88.1 to 97.5.95.25497.5.95.2552,046
4597.5.96.0/2197.5.96.1 to 97.5.103.25497.5.103.2552,046
4697.5.104.0/2197.5.104.1 to 97.5.111.25497.5.111.2552,046
4797.5.112.0/2197.5.112.1 to 97.5.119.25497.5.119.2552,046
4897.5.120.0/2197.5.120.1 to 97.5.127.25497.5.127.2552,046
4997.5.128.0/2197.5.128.1 to 97.5.135.25497.5.135.2552,046
5097.5.136.0/2197.5.136.1 to 97.5.143.25497.5.143.2552,046
5197.5.144.0/2197.5.144.1 to 97.5.151.25497.5.151.2552,046
5297.5.152.0/2197.5.152.1 to 97.5.159.25497.5.159.2552,046
5397.5.160.0/2197.5.160.1 to 97.5.167.25497.5.167.2552,046
5497.5.168.0/2197.5.168.1 to 97.5.175.25497.5.175.2552,046
5597.5.176.0/2197.5.176.1 to 97.5.183.25497.5.183.2552,046
5697.5.184.0/2197.5.184.1 to 97.5.191.25497.5.191.2552,046
5797.5.192.0/2197.5.192.1 to 97.5.199.25497.5.199.2552,046
5897.5.200.0/2197.5.200.1 to 97.5.207.25497.5.207.2552,046
5997.5.208.0/2197.5.208.1 to 97.5.215.25497.5.215.2552,046
6097.5.216.0/2197.5.216.1 to 97.5.223.25497.5.223.2552,046
6197.5.224.0/2197.5.224.1 to 97.5.231.25497.5.231.2552,046
6297.5.232.0/2197.5.232.1 to 97.5.239.25497.5.239.2552,046
6397.5.240.0/2197.5.240.1 to 97.5.247.25497.5.247.2552,046
6497.5.248.0/2197.5.248.1 to 97.5.255.25497.5.255.2552,046

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.