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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.

Network115.0.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
115.0.0.0
Broadcast address
115.0.127.255
First usable
115.0.0.1
Last usable
115.0.127.254
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 73000000 · Integer 1929379840 to 1929412607
Reverse DNS zones
0.0.115.in-addr.arpa
1.0.115.in-addr.arpa
2.0.115.in-addr.arpa
3.0.115.in-addr.arpa
4.0.115.in-addr.arpa
5.0.115.in-addr.arpa
6.0.115.in-addr.arpa
7.0.115.in-addr.arpa
8.0.115.in-addr.arpa
9.0.115.in-addr.arpa
10.0.115.in-addr.arpa
11.0.115.in-addr.arpa
12.0.115.in-addr.arpa
13.0.115.in-addr.arpa
14.0.115.in-addr.arpa
15.0.115.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
Address01110011.00000000.00000000.00000000115.0.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network01110011.00000000.00000000.00000000115.0.0.0
Broadcast01110011.00000000.01111111.11111111115.0.127.255
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)

115.0.0.0/17 makes 128 subnets of /24.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1115.0.0.0/24115.0.0.1 to 115.0.0.254115.0.0.255254
2115.0.1.0/24115.0.1.1 to 115.0.1.254115.0.1.255254
3115.0.2.0/24115.0.2.1 to 115.0.2.254115.0.2.255254
4115.0.3.0/24115.0.3.1 to 115.0.3.254115.0.3.255254
5115.0.4.0/24115.0.4.1 to 115.0.4.254115.0.4.255254
6115.0.5.0/24115.0.5.1 to 115.0.5.254115.0.5.255254
7115.0.6.0/24115.0.6.1 to 115.0.6.254115.0.6.255254
8115.0.7.0/24115.0.7.1 to 115.0.7.254115.0.7.255254
9115.0.8.0/24115.0.8.1 to 115.0.8.254115.0.8.255254
10115.0.9.0/24115.0.9.1 to 115.0.9.254115.0.9.255254
11115.0.10.0/24115.0.10.1 to 115.0.10.254115.0.10.255254
12115.0.11.0/24115.0.11.1 to 115.0.11.254115.0.11.255254
13115.0.12.0/24115.0.12.1 to 115.0.12.254115.0.12.255254
14115.0.13.0/24115.0.13.1 to 115.0.13.254115.0.13.255254
15115.0.14.0/24115.0.14.1 to 115.0.14.254115.0.14.255254
16115.0.15.0/24115.0.15.1 to 115.0.15.254115.0.15.255254
17115.0.16.0/24115.0.16.1 to 115.0.16.254115.0.16.255254
18115.0.17.0/24115.0.17.1 to 115.0.17.254115.0.17.255254
19115.0.18.0/24115.0.18.1 to 115.0.18.254115.0.18.255254
20115.0.19.0/24115.0.19.1 to 115.0.19.254115.0.19.255254
21115.0.20.0/24115.0.20.1 to 115.0.20.254115.0.20.255254
22115.0.21.0/24115.0.21.1 to 115.0.21.254115.0.21.255254
23115.0.22.0/24115.0.22.1 to 115.0.22.254115.0.22.255254
24115.0.23.0/24115.0.23.1 to 115.0.23.254115.0.23.255254
25115.0.24.0/24115.0.24.1 to 115.0.24.254115.0.24.255254
26115.0.25.0/24115.0.25.1 to 115.0.25.254115.0.25.255254
27115.0.26.0/24115.0.26.1 to 115.0.26.254115.0.26.255254
28115.0.27.0/24115.0.27.1 to 115.0.27.254115.0.27.255254
29115.0.28.0/24115.0.28.1 to 115.0.28.254115.0.28.255254
30115.0.29.0/24115.0.29.1 to 115.0.29.254115.0.29.255254
31115.0.30.0/24115.0.30.1 to 115.0.30.254115.0.30.255254
32115.0.31.0/24115.0.31.1 to 115.0.31.254115.0.31.255254
33115.0.32.0/24115.0.32.1 to 115.0.32.254115.0.32.255254
34115.0.33.0/24115.0.33.1 to 115.0.33.254115.0.33.255254
35115.0.34.0/24115.0.34.1 to 115.0.34.254115.0.34.255254
36115.0.35.0/24115.0.35.1 to 115.0.35.254115.0.35.255254
37115.0.36.0/24115.0.36.1 to 115.0.36.254115.0.36.255254
38115.0.37.0/24115.0.37.1 to 115.0.37.254115.0.37.255254
39115.0.38.0/24115.0.38.1 to 115.0.38.254115.0.38.255254
40115.0.39.0/24115.0.39.1 to 115.0.39.254115.0.39.255254
41115.0.40.0/24115.0.40.1 to 115.0.40.254115.0.40.255254
42115.0.41.0/24115.0.41.1 to 115.0.41.254115.0.41.255254
43115.0.42.0/24115.0.42.1 to 115.0.42.254115.0.42.255254
44115.0.43.0/24115.0.43.1 to 115.0.43.254115.0.43.255254
45115.0.44.0/24115.0.44.1 to 115.0.44.254115.0.44.255254
46115.0.45.0/24115.0.45.1 to 115.0.45.254115.0.45.255254
47115.0.46.0/24115.0.46.1 to 115.0.46.254115.0.46.255254
48115.0.47.0/24115.0.47.1 to 115.0.47.254115.0.47.255254
49115.0.48.0/24115.0.48.1 to 115.0.48.254115.0.48.255254
50115.0.49.0/24115.0.49.1 to 115.0.49.254115.0.49.255254
51115.0.50.0/24115.0.50.1 to 115.0.50.254115.0.50.255254
52115.0.51.0/24115.0.51.1 to 115.0.51.254115.0.51.255254
53115.0.52.0/24115.0.52.1 to 115.0.52.254115.0.52.255254
54115.0.53.0/24115.0.53.1 to 115.0.53.254115.0.53.255254
55115.0.54.0/24115.0.54.1 to 115.0.54.254115.0.54.255254
56115.0.55.0/24115.0.55.1 to 115.0.55.254115.0.55.255254
57115.0.56.0/24115.0.56.1 to 115.0.56.254115.0.56.255254
58115.0.57.0/24115.0.57.1 to 115.0.57.254115.0.57.255254
59115.0.58.0/24115.0.58.1 to 115.0.58.254115.0.58.255254
60115.0.59.0/24115.0.59.1 to 115.0.59.254115.0.59.255254
61115.0.60.0/24115.0.60.1 to 115.0.60.254115.0.60.255254
62115.0.61.0/24115.0.61.1 to 115.0.61.254115.0.61.255254
63115.0.62.0/24115.0.62.1 to 115.0.62.254115.0.62.255254
64115.0.63.0/24115.0.63.1 to 115.0.63.254115.0.63.255254
65115.0.64.0/24115.0.64.1 to 115.0.64.254115.0.64.255254
66115.0.65.0/24115.0.65.1 to 115.0.65.254115.0.65.255254
67115.0.66.0/24115.0.66.1 to 115.0.66.254115.0.66.255254
68115.0.67.0/24115.0.67.1 to 115.0.67.254115.0.67.255254
69115.0.68.0/24115.0.68.1 to 115.0.68.254115.0.68.255254
70115.0.69.0/24115.0.69.1 to 115.0.69.254115.0.69.255254
71115.0.70.0/24115.0.70.1 to 115.0.70.254115.0.70.255254
72115.0.71.0/24115.0.71.1 to 115.0.71.254115.0.71.255254
73115.0.72.0/24115.0.72.1 to 115.0.72.254115.0.72.255254
74115.0.73.0/24115.0.73.1 to 115.0.73.254115.0.73.255254
75115.0.74.0/24115.0.74.1 to 115.0.74.254115.0.74.255254
76115.0.75.0/24115.0.75.1 to 115.0.75.254115.0.75.255254
77115.0.76.0/24115.0.76.1 to 115.0.76.254115.0.76.255254
78115.0.77.0/24115.0.77.1 to 115.0.77.254115.0.77.255254
79115.0.78.0/24115.0.78.1 to 115.0.78.254115.0.78.255254
80115.0.79.0/24115.0.79.1 to 115.0.79.254115.0.79.255254
81115.0.80.0/24115.0.80.1 to 115.0.80.254115.0.80.255254
82115.0.81.0/24115.0.81.1 to 115.0.81.254115.0.81.255254
83115.0.82.0/24115.0.82.1 to 115.0.82.254115.0.82.255254
84115.0.83.0/24115.0.83.1 to 115.0.83.254115.0.83.255254
85115.0.84.0/24115.0.84.1 to 115.0.84.254115.0.84.255254
86115.0.85.0/24115.0.85.1 to 115.0.85.254115.0.85.255254
87115.0.86.0/24115.0.86.1 to 115.0.86.254115.0.86.255254
88115.0.87.0/24115.0.87.1 to 115.0.87.254115.0.87.255254
89115.0.88.0/24115.0.88.1 to 115.0.88.254115.0.88.255254
90115.0.89.0/24115.0.89.1 to 115.0.89.254115.0.89.255254
91115.0.90.0/24115.0.90.1 to 115.0.90.254115.0.90.255254
92115.0.91.0/24115.0.91.1 to 115.0.91.254115.0.91.255254
93115.0.92.0/24115.0.92.1 to 115.0.92.254115.0.92.255254
94115.0.93.0/24115.0.93.1 to 115.0.93.254115.0.93.255254
95115.0.94.0/24115.0.94.1 to 115.0.94.254115.0.94.255254
96115.0.95.0/24115.0.95.1 to 115.0.95.254115.0.95.255254
97115.0.96.0/24115.0.96.1 to 115.0.96.254115.0.96.255254
98115.0.97.0/24115.0.97.1 to 115.0.97.254115.0.97.255254
99115.0.98.0/24115.0.98.1 to 115.0.98.254115.0.98.255254
100115.0.99.0/24115.0.99.1 to 115.0.99.254115.0.99.255254
101115.0.100.0/24115.0.100.1 to 115.0.100.254115.0.100.255254
102115.0.101.0/24115.0.101.1 to 115.0.101.254115.0.101.255254
103115.0.102.0/24115.0.102.1 to 115.0.102.254115.0.102.255254
104115.0.103.0/24115.0.103.1 to 115.0.103.254115.0.103.255254
105115.0.104.0/24115.0.104.1 to 115.0.104.254115.0.104.255254
106115.0.105.0/24115.0.105.1 to 115.0.105.254115.0.105.255254
107115.0.106.0/24115.0.106.1 to 115.0.106.254115.0.106.255254
108115.0.107.0/24115.0.107.1 to 115.0.107.254115.0.107.255254
109115.0.108.0/24115.0.108.1 to 115.0.108.254115.0.108.255254
110115.0.109.0/24115.0.109.1 to 115.0.109.254115.0.109.255254
111115.0.110.0/24115.0.110.1 to 115.0.110.254115.0.110.255254
112115.0.111.0/24115.0.111.1 to 115.0.111.254115.0.111.255254
113115.0.112.0/24115.0.112.1 to 115.0.112.254115.0.112.255254
114115.0.113.0/24115.0.113.1 to 115.0.113.254115.0.113.255254
115115.0.114.0/24115.0.114.1 to 115.0.114.254115.0.114.255254
116115.0.115.0/24115.0.115.1 to 115.0.115.254115.0.115.255254
117115.0.116.0/24115.0.116.1 to 115.0.116.254115.0.116.255254
118115.0.117.0/24115.0.117.1 to 115.0.117.254115.0.117.255254
119115.0.118.0/24115.0.118.1 to 115.0.118.254115.0.118.255254
120115.0.119.0/24115.0.119.1 to 115.0.119.254115.0.119.255254
121115.0.120.0/24115.0.120.1 to 115.0.120.254115.0.120.255254
122115.0.121.0/24115.0.121.1 to 115.0.121.254115.0.121.255254
123115.0.122.0/24115.0.122.1 to 115.0.122.254115.0.122.255254
124115.0.123.0/24115.0.123.1 to 115.0.123.254115.0.123.255254
125115.0.124.0/24115.0.124.1 to 115.0.124.254115.0.124.255254
126115.0.125.0/24115.0.125.1 to 115.0.125.254115.0.125.255254
127115.0.126.0/24115.0.126.1 to 115.0.126.254115.0.126.255254
128115.0.127.0/24115.0.127.1 to 115.0.127.254115.0.127.255254

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.