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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.

Network24.0.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
24.0.0.0
Broadcast address
24.0.127.255
First usable
24.0.0.1
Last usable
24.0.127.254
Usable hosts
32,766 (32,768 less the network and broadcast addresses)
Subnet mask
255.255.128.0
Wildcard mask
0.0.127.255 (Cisco ACLs, OSPF)
Prefix length
/17
Type
Public public
Old class
A (default /8)
As numbers
Hex 18000000 · Integer 402653184 to 402685951
Reverse DNS zones
0.0.24.in-addr.arpa
1.0.24.in-addr.arpa
2.0.24.in-addr.arpa
3.0.24.in-addr.arpa
4.0.24.in-addr.arpa
5.0.24.in-addr.arpa
6.0.24.in-addr.arpa
7.0.24.in-addr.arpa
8.0.24.in-addr.arpa
9.0.24.in-addr.arpa
10.0.24.in-addr.arpa
11.0.24.in-addr.arpa
12.0.24.in-addr.arpa
13.0.24.in-addr.arpa
14.0.24.in-addr.arpa
15.0.24.in-addr.arpa
and 112 more
/17 is not on a 8-bit boundary, so it takes 128 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00011000.00000000.00000000.0000000024.0.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network00011000.00000000.00000000.0000000024.0.0.0
Broadcast00011000.00000000.01111111.1111111124.0.127.255
Split into smaller subnets/24
/18 (2)/19 (4)/20 (8)/21 (16)/22 (32)/23 (64)/24 (128)/25 (256)/26 (512)/27 (1,024)/28 (2,048)/29 (4,096)

24.0.0.0/17 makes 128 subnets of /24.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
124.0.0.0/2424.0.0.1 to 24.0.0.25424.0.0.255254
224.0.1.0/2424.0.1.1 to 24.0.1.25424.0.1.255254
324.0.2.0/2424.0.2.1 to 24.0.2.25424.0.2.255254
424.0.3.0/2424.0.3.1 to 24.0.3.25424.0.3.255254
524.0.4.0/2424.0.4.1 to 24.0.4.25424.0.4.255254
624.0.5.0/2424.0.5.1 to 24.0.5.25424.0.5.255254
724.0.6.0/2424.0.6.1 to 24.0.6.25424.0.6.255254
824.0.7.0/2424.0.7.1 to 24.0.7.25424.0.7.255254
924.0.8.0/2424.0.8.1 to 24.0.8.25424.0.8.255254
1024.0.9.0/2424.0.9.1 to 24.0.9.25424.0.9.255254
1124.0.10.0/2424.0.10.1 to 24.0.10.25424.0.10.255254
1224.0.11.0/2424.0.11.1 to 24.0.11.25424.0.11.255254
1324.0.12.0/2424.0.12.1 to 24.0.12.25424.0.12.255254
1424.0.13.0/2424.0.13.1 to 24.0.13.25424.0.13.255254
1524.0.14.0/2424.0.14.1 to 24.0.14.25424.0.14.255254
1624.0.15.0/2424.0.15.1 to 24.0.15.25424.0.15.255254
1724.0.16.0/2424.0.16.1 to 24.0.16.25424.0.16.255254
1824.0.17.0/2424.0.17.1 to 24.0.17.25424.0.17.255254
1924.0.18.0/2424.0.18.1 to 24.0.18.25424.0.18.255254
2024.0.19.0/2424.0.19.1 to 24.0.19.25424.0.19.255254
2124.0.20.0/2424.0.20.1 to 24.0.20.25424.0.20.255254
2224.0.21.0/2424.0.21.1 to 24.0.21.25424.0.21.255254
2324.0.22.0/2424.0.22.1 to 24.0.22.25424.0.22.255254
2424.0.23.0/2424.0.23.1 to 24.0.23.25424.0.23.255254
2524.0.24.0/2424.0.24.1 to 24.0.24.25424.0.24.255254
2624.0.25.0/2424.0.25.1 to 24.0.25.25424.0.25.255254
2724.0.26.0/2424.0.26.1 to 24.0.26.25424.0.26.255254
2824.0.27.0/2424.0.27.1 to 24.0.27.25424.0.27.255254
2924.0.28.0/2424.0.28.1 to 24.0.28.25424.0.28.255254
3024.0.29.0/2424.0.29.1 to 24.0.29.25424.0.29.255254
3124.0.30.0/2424.0.30.1 to 24.0.30.25424.0.30.255254
3224.0.31.0/2424.0.31.1 to 24.0.31.25424.0.31.255254
3324.0.32.0/2424.0.32.1 to 24.0.32.25424.0.32.255254
3424.0.33.0/2424.0.33.1 to 24.0.33.25424.0.33.255254
3524.0.34.0/2424.0.34.1 to 24.0.34.25424.0.34.255254
3624.0.35.0/2424.0.35.1 to 24.0.35.25424.0.35.255254
3724.0.36.0/2424.0.36.1 to 24.0.36.25424.0.36.255254
3824.0.37.0/2424.0.37.1 to 24.0.37.25424.0.37.255254
3924.0.38.0/2424.0.38.1 to 24.0.38.25424.0.38.255254
4024.0.39.0/2424.0.39.1 to 24.0.39.25424.0.39.255254
4124.0.40.0/2424.0.40.1 to 24.0.40.25424.0.40.255254
4224.0.41.0/2424.0.41.1 to 24.0.41.25424.0.41.255254
4324.0.42.0/2424.0.42.1 to 24.0.42.25424.0.42.255254
4424.0.43.0/2424.0.43.1 to 24.0.43.25424.0.43.255254
4524.0.44.0/2424.0.44.1 to 24.0.44.25424.0.44.255254
4624.0.45.0/2424.0.45.1 to 24.0.45.25424.0.45.255254
4724.0.46.0/2424.0.46.1 to 24.0.46.25424.0.46.255254
4824.0.47.0/2424.0.47.1 to 24.0.47.25424.0.47.255254
4924.0.48.0/2424.0.48.1 to 24.0.48.25424.0.48.255254
5024.0.49.0/2424.0.49.1 to 24.0.49.25424.0.49.255254
5124.0.50.0/2424.0.50.1 to 24.0.50.25424.0.50.255254
5224.0.51.0/2424.0.51.1 to 24.0.51.25424.0.51.255254
5324.0.52.0/2424.0.52.1 to 24.0.52.25424.0.52.255254
5424.0.53.0/2424.0.53.1 to 24.0.53.25424.0.53.255254
5524.0.54.0/2424.0.54.1 to 24.0.54.25424.0.54.255254
5624.0.55.0/2424.0.55.1 to 24.0.55.25424.0.55.255254
5724.0.56.0/2424.0.56.1 to 24.0.56.25424.0.56.255254
5824.0.57.0/2424.0.57.1 to 24.0.57.25424.0.57.255254
5924.0.58.0/2424.0.58.1 to 24.0.58.25424.0.58.255254
6024.0.59.0/2424.0.59.1 to 24.0.59.25424.0.59.255254
6124.0.60.0/2424.0.60.1 to 24.0.60.25424.0.60.255254
6224.0.61.0/2424.0.61.1 to 24.0.61.25424.0.61.255254
6324.0.62.0/2424.0.62.1 to 24.0.62.25424.0.62.255254
6424.0.63.0/2424.0.63.1 to 24.0.63.25424.0.63.255254
6524.0.64.0/2424.0.64.1 to 24.0.64.25424.0.64.255254
6624.0.65.0/2424.0.65.1 to 24.0.65.25424.0.65.255254
6724.0.66.0/2424.0.66.1 to 24.0.66.25424.0.66.255254
6824.0.67.0/2424.0.67.1 to 24.0.67.25424.0.67.255254
6924.0.68.0/2424.0.68.1 to 24.0.68.25424.0.68.255254
7024.0.69.0/2424.0.69.1 to 24.0.69.25424.0.69.255254
7124.0.70.0/2424.0.70.1 to 24.0.70.25424.0.70.255254
7224.0.71.0/2424.0.71.1 to 24.0.71.25424.0.71.255254
7324.0.72.0/2424.0.72.1 to 24.0.72.25424.0.72.255254
7424.0.73.0/2424.0.73.1 to 24.0.73.25424.0.73.255254
7524.0.74.0/2424.0.74.1 to 24.0.74.25424.0.74.255254
7624.0.75.0/2424.0.75.1 to 24.0.75.25424.0.75.255254
7724.0.76.0/2424.0.76.1 to 24.0.76.25424.0.76.255254
7824.0.77.0/2424.0.77.1 to 24.0.77.25424.0.77.255254
7924.0.78.0/2424.0.78.1 to 24.0.78.25424.0.78.255254
8024.0.79.0/2424.0.79.1 to 24.0.79.25424.0.79.255254
8124.0.80.0/2424.0.80.1 to 24.0.80.25424.0.80.255254
8224.0.81.0/2424.0.81.1 to 24.0.81.25424.0.81.255254
8324.0.82.0/2424.0.82.1 to 24.0.82.25424.0.82.255254
8424.0.83.0/2424.0.83.1 to 24.0.83.25424.0.83.255254
8524.0.84.0/2424.0.84.1 to 24.0.84.25424.0.84.255254
8624.0.85.0/2424.0.85.1 to 24.0.85.25424.0.85.255254
8724.0.86.0/2424.0.86.1 to 24.0.86.25424.0.86.255254
8824.0.87.0/2424.0.87.1 to 24.0.87.25424.0.87.255254
8924.0.88.0/2424.0.88.1 to 24.0.88.25424.0.88.255254
9024.0.89.0/2424.0.89.1 to 24.0.89.25424.0.89.255254
9124.0.90.0/2424.0.90.1 to 24.0.90.25424.0.90.255254
9224.0.91.0/2424.0.91.1 to 24.0.91.25424.0.91.255254
9324.0.92.0/2424.0.92.1 to 24.0.92.25424.0.92.255254
9424.0.93.0/2424.0.93.1 to 24.0.93.25424.0.93.255254
9524.0.94.0/2424.0.94.1 to 24.0.94.25424.0.94.255254
9624.0.95.0/2424.0.95.1 to 24.0.95.25424.0.95.255254
9724.0.96.0/2424.0.96.1 to 24.0.96.25424.0.96.255254
9824.0.97.0/2424.0.97.1 to 24.0.97.25424.0.97.255254
9924.0.98.0/2424.0.98.1 to 24.0.98.25424.0.98.255254
10024.0.99.0/2424.0.99.1 to 24.0.99.25424.0.99.255254
10124.0.100.0/2424.0.100.1 to 24.0.100.25424.0.100.255254
10224.0.101.0/2424.0.101.1 to 24.0.101.25424.0.101.255254
10324.0.102.0/2424.0.102.1 to 24.0.102.25424.0.102.255254
10424.0.103.0/2424.0.103.1 to 24.0.103.25424.0.103.255254
10524.0.104.0/2424.0.104.1 to 24.0.104.25424.0.104.255254
10624.0.105.0/2424.0.105.1 to 24.0.105.25424.0.105.255254
10724.0.106.0/2424.0.106.1 to 24.0.106.25424.0.106.255254
10824.0.107.0/2424.0.107.1 to 24.0.107.25424.0.107.255254
10924.0.108.0/2424.0.108.1 to 24.0.108.25424.0.108.255254
11024.0.109.0/2424.0.109.1 to 24.0.109.25424.0.109.255254
11124.0.110.0/2424.0.110.1 to 24.0.110.25424.0.110.255254
11224.0.111.0/2424.0.111.1 to 24.0.111.25424.0.111.255254
11324.0.112.0/2424.0.112.1 to 24.0.112.25424.0.112.255254
11424.0.113.0/2424.0.113.1 to 24.0.113.25424.0.113.255254
11524.0.114.0/2424.0.114.1 to 24.0.114.25424.0.114.255254
11624.0.115.0/2424.0.115.1 to 24.0.115.25424.0.115.255254
11724.0.116.0/2424.0.116.1 to 24.0.116.25424.0.116.255254
11824.0.117.0/2424.0.117.1 to 24.0.117.25424.0.117.255254
11924.0.118.0/2424.0.118.1 to 24.0.118.25424.0.118.255254
12024.0.119.0/2424.0.119.1 to 24.0.119.25424.0.119.255254
12124.0.120.0/2424.0.120.1 to 24.0.120.25424.0.120.255254
12224.0.121.0/2424.0.121.1 to 24.0.121.25424.0.121.255254
12324.0.122.0/2424.0.122.1 to 24.0.122.25424.0.122.255254
12424.0.123.0/2424.0.123.1 to 24.0.123.25424.0.123.255254
12524.0.124.0/2424.0.124.1 to 24.0.124.25424.0.124.255254
12624.0.125.0/2424.0.125.1 to 24.0.125.25424.0.125.255254
12724.0.126.0/2424.0.126.1 to 24.0.126.25424.0.126.255254
12824.0.127.0/2424.0.127.1 to 24.0.127.25424.0.127.255254

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.