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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.

Network161.0.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
161.0.0.0
Broadcast address
161.63.255.255
First usable
161.0.0.1
Last usable
161.63.255.254
Usable hosts
4,194,302 (4,194,304 less the network and broadcast addresses)
Subnet mask
255.192.0.0
Wildcard mask
0.63.255.255 (Cisco ACLs, OSPF)
Prefix length
/10
Type
Public public
Old class
B (default /16)
As numbers
Hex A1000000 · Integer 2701131776 to 2705326079
Reverse DNS zones
0.161.in-addr.arpa
1.161.in-addr.arpa
2.161.in-addr.arpa
3.161.in-addr.arpa
4.161.in-addr.arpa
5.161.in-addr.arpa
6.161.in-addr.arpa
7.161.in-addr.arpa
8.161.in-addr.arpa
9.161.in-addr.arpa
10.161.in-addr.arpa
11.161.in-addr.arpa
12.161.in-addr.arpa
13.161.in-addr.arpa
14.161.in-addr.arpa
15.161.in-addr.arpa
and 48 more
/10 is not on a 8-bit boundary, so it takes 64 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10100001.00000000.00000000.00000000161.0.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network10100001.00000000.00000000.00000000161.0.0.0
Broadcast10100001.00111111.11111111.11111111161.63.255.255
Split into smaller subnets/17
/11 (2)/12 (4)/13 (8)/14 (16)/15 (32)/16 (64)/17 (128)/18 (256)/19 (512)/20 (1,024)/21 (2,048)/22 (4,096)

161.0.0.0/10 makes 128 subnets of /17.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1161.0.0.0/17161.0.0.1 to 161.0.127.254161.0.127.25532,766
2161.0.128.0/17161.0.128.1 to 161.0.255.254161.0.255.25532,766
3161.1.0.0/17161.1.0.1 to 161.1.127.254161.1.127.25532,766
4161.1.128.0/17161.1.128.1 to 161.1.255.254161.1.255.25532,766
5161.2.0.0/17161.2.0.1 to 161.2.127.254161.2.127.25532,766
6161.2.128.0/17161.2.128.1 to 161.2.255.254161.2.255.25532,766
7161.3.0.0/17161.3.0.1 to 161.3.127.254161.3.127.25532,766
8161.3.128.0/17161.3.128.1 to 161.3.255.254161.3.255.25532,766
9161.4.0.0/17161.4.0.1 to 161.4.127.254161.4.127.25532,766
10161.4.128.0/17161.4.128.1 to 161.4.255.254161.4.255.25532,766
11161.5.0.0/17161.5.0.1 to 161.5.127.254161.5.127.25532,766
12161.5.128.0/17161.5.128.1 to 161.5.255.254161.5.255.25532,766
13161.6.0.0/17161.6.0.1 to 161.6.127.254161.6.127.25532,766
14161.6.128.0/17161.6.128.1 to 161.6.255.254161.6.255.25532,766
15161.7.0.0/17161.7.0.1 to 161.7.127.254161.7.127.25532,766
16161.7.128.0/17161.7.128.1 to 161.7.255.254161.7.255.25532,766
17161.8.0.0/17161.8.0.1 to 161.8.127.254161.8.127.25532,766
18161.8.128.0/17161.8.128.1 to 161.8.255.254161.8.255.25532,766
19161.9.0.0/17161.9.0.1 to 161.9.127.254161.9.127.25532,766
20161.9.128.0/17161.9.128.1 to 161.9.255.254161.9.255.25532,766
21161.10.0.0/17161.10.0.1 to 161.10.127.254161.10.127.25532,766
22161.10.128.0/17161.10.128.1 to 161.10.255.254161.10.255.25532,766
23161.11.0.0/17161.11.0.1 to 161.11.127.254161.11.127.25532,766
24161.11.128.0/17161.11.128.1 to 161.11.255.254161.11.255.25532,766
25161.12.0.0/17161.12.0.1 to 161.12.127.254161.12.127.25532,766
26161.12.128.0/17161.12.128.1 to 161.12.255.254161.12.255.25532,766
27161.13.0.0/17161.13.0.1 to 161.13.127.254161.13.127.25532,766
28161.13.128.0/17161.13.128.1 to 161.13.255.254161.13.255.25532,766
29161.14.0.0/17161.14.0.1 to 161.14.127.254161.14.127.25532,766
30161.14.128.0/17161.14.128.1 to 161.14.255.254161.14.255.25532,766
31161.15.0.0/17161.15.0.1 to 161.15.127.254161.15.127.25532,766
32161.15.128.0/17161.15.128.1 to 161.15.255.254161.15.255.25532,766
33161.16.0.0/17161.16.0.1 to 161.16.127.254161.16.127.25532,766
34161.16.128.0/17161.16.128.1 to 161.16.255.254161.16.255.25532,766
35161.17.0.0/17161.17.0.1 to 161.17.127.254161.17.127.25532,766
36161.17.128.0/17161.17.128.1 to 161.17.255.254161.17.255.25532,766
37161.18.0.0/17161.18.0.1 to 161.18.127.254161.18.127.25532,766
38161.18.128.0/17161.18.128.1 to 161.18.255.254161.18.255.25532,766
39161.19.0.0/17161.19.0.1 to 161.19.127.254161.19.127.25532,766
40161.19.128.0/17161.19.128.1 to 161.19.255.254161.19.255.25532,766
41161.20.0.0/17161.20.0.1 to 161.20.127.254161.20.127.25532,766
42161.20.128.0/17161.20.128.1 to 161.20.255.254161.20.255.25532,766
43161.21.0.0/17161.21.0.1 to 161.21.127.254161.21.127.25532,766
44161.21.128.0/17161.21.128.1 to 161.21.255.254161.21.255.25532,766
45161.22.0.0/17161.22.0.1 to 161.22.127.254161.22.127.25532,766
46161.22.128.0/17161.22.128.1 to 161.22.255.254161.22.255.25532,766
47161.23.0.0/17161.23.0.1 to 161.23.127.254161.23.127.25532,766
48161.23.128.0/17161.23.128.1 to 161.23.255.254161.23.255.25532,766
49161.24.0.0/17161.24.0.1 to 161.24.127.254161.24.127.25532,766
50161.24.128.0/17161.24.128.1 to 161.24.255.254161.24.255.25532,766
51161.25.0.0/17161.25.0.1 to 161.25.127.254161.25.127.25532,766
52161.25.128.0/17161.25.128.1 to 161.25.255.254161.25.255.25532,766
53161.26.0.0/17161.26.0.1 to 161.26.127.254161.26.127.25532,766
54161.26.128.0/17161.26.128.1 to 161.26.255.254161.26.255.25532,766
55161.27.0.0/17161.27.0.1 to 161.27.127.254161.27.127.25532,766
56161.27.128.0/17161.27.128.1 to 161.27.255.254161.27.255.25532,766
57161.28.0.0/17161.28.0.1 to 161.28.127.254161.28.127.25532,766
58161.28.128.0/17161.28.128.1 to 161.28.255.254161.28.255.25532,766
59161.29.0.0/17161.29.0.1 to 161.29.127.254161.29.127.25532,766
60161.29.128.0/17161.29.128.1 to 161.29.255.254161.29.255.25532,766
61161.30.0.0/17161.30.0.1 to 161.30.127.254161.30.127.25532,766
62161.30.128.0/17161.30.128.1 to 161.30.255.254161.30.255.25532,766
63161.31.0.0/17161.31.0.1 to 161.31.127.254161.31.127.25532,766
64161.31.128.0/17161.31.128.1 to 161.31.255.254161.31.255.25532,766
65161.32.0.0/17161.32.0.1 to 161.32.127.254161.32.127.25532,766
66161.32.128.0/17161.32.128.1 to 161.32.255.254161.32.255.25532,766
67161.33.0.0/17161.33.0.1 to 161.33.127.254161.33.127.25532,766
68161.33.128.0/17161.33.128.1 to 161.33.255.254161.33.255.25532,766
69161.34.0.0/17161.34.0.1 to 161.34.127.254161.34.127.25532,766
70161.34.128.0/17161.34.128.1 to 161.34.255.254161.34.255.25532,766
71161.35.0.0/17161.35.0.1 to 161.35.127.254161.35.127.25532,766
72161.35.128.0/17161.35.128.1 to 161.35.255.254161.35.255.25532,766
73161.36.0.0/17161.36.0.1 to 161.36.127.254161.36.127.25532,766
74161.36.128.0/17161.36.128.1 to 161.36.255.254161.36.255.25532,766
75161.37.0.0/17161.37.0.1 to 161.37.127.254161.37.127.25532,766
76161.37.128.0/17161.37.128.1 to 161.37.255.254161.37.255.25532,766
77161.38.0.0/17161.38.0.1 to 161.38.127.254161.38.127.25532,766
78161.38.128.0/17161.38.128.1 to 161.38.255.254161.38.255.25532,766
79161.39.0.0/17161.39.0.1 to 161.39.127.254161.39.127.25532,766
80161.39.128.0/17161.39.128.1 to 161.39.255.254161.39.255.25532,766
81161.40.0.0/17161.40.0.1 to 161.40.127.254161.40.127.25532,766
82161.40.128.0/17161.40.128.1 to 161.40.255.254161.40.255.25532,766
83161.41.0.0/17161.41.0.1 to 161.41.127.254161.41.127.25532,766
84161.41.128.0/17161.41.128.1 to 161.41.255.254161.41.255.25532,766
85161.42.0.0/17161.42.0.1 to 161.42.127.254161.42.127.25532,766
86161.42.128.0/17161.42.128.1 to 161.42.255.254161.42.255.25532,766
87161.43.0.0/17161.43.0.1 to 161.43.127.254161.43.127.25532,766
88161.43.128.0/17161.43.128.1 to 161.43.255.254161.43.255.25532,766
89161.44.0.0/17161.44.0.1 to 161.44.127.254161.44.127.25532,766
90161.44.128.0/17161.44.128.1 to 161.44.255.254161.44.255.25532,766
91161.45.0.0/17161.45.0.1 to 161.45.127.254161.45.127.25532,766
92161.45.128.0/17161.45.128.1 to 161.45.255.254161.45.255.25532,766
93161.46.0.0/17161.46.0.1 to 161.46.127.254161.46.127.25532,766
94161.46.128.0/17161.46.128.1 to 161.46.255.254161.46.255.25532,766
95161.47.0.0/17161.47.0.1 to 161.47.127.254161.47.127.25532,766
96161.47.128.0/17161.47.128.1 to 161.47.255.254161.47.255.25532,766
97161.48.0.0/17161.48.0.1 to 161.48.127.254161.48.127.25532,766
98161.48.128.0/17161.48.128.1 to 161.48.255.254161.48.255.25532,766
99161.49.0.0/17161.49.0.1 to 161.49.127.254161.49.127.25532,766
100161.49.128.0/17161.49.128.1 to 161.49.255.254161.49.255.25532,766
101161.50.0.0/17161.50.0.1 to 161.50.127.254161.50.127.25532,766
102161.50.128.0/17161.50.128.1 to 161.50.255.254161.50.255.25532,766
103161.51.0.0/17161.51.0.1 to 161.51.127.254161.51.127.25532,766
104161.51.128.0/17161.51.128.1 to 161.51.255.254161.51.255.25532,766
105161.52.0.0/17161.52.0.1 to 161.52.127.254161.52.127.25532,766
106161.52.128.0/17161.52.128.1 to 161.52.255.254161.52.255.25532,766
107161.53.0.0/17161.53.0.1 to 161.53.127.254161.53.127.25532,766
108161.53.128.0/17161.53.128.1 to 161.53.255.254161.53.255.25532,766
109161.54.0.0/17161.54.0.1 to 161.54.127.254161.54.127.25532,766
110161.54.128.0/17161.54.128.1 to 161.54.255.254161.54.255.25532,766
111161.55.0.0/17161.55.0.1 to 161.55.127.254161.55.127.25532,766
112161.55.128.0/17161.55.128.1 to 161.55.255.254161.55.255.25532,766
113161.56.0.0/17161.56.0.1 to 161.56.127.254161.56.127.25532,766
114161.56.128.0/17161.56.128.1 to 161.56.255.254161.56.255.25532,766
115161.57.0.0/17161.57.0.1 to 161.57.127.254161.57.127.25532,766
116161.57.128.0/17161.57.128.1 to 161.57.255.254161.57.255.25532,766
117161.58.0.0/17161.58.0.1 to 161.58.127.254161.58.127.25532,766
118161.58.128.0/17161.58.128.1 to 161.58.255.254161.58.255.25532,766
119161.59.0.0/17161.59.0.1 to 161.59.127.254161.59.127.25532,766
120161.59.128.0/17161.59.128.1 to 161.59.255.254161.59.255.25532,766
121161.60.0.0/17161.60.0.1 to 161.60.127.254161.60.127.25532,766
122161.60.128.0/17161.60.128.1 to 161.60.255.254161.60.255.25532,766
123161.61.0.0/17161.61.0.1 to 161.61.127.254161.61.127.25532,766
124161.61.128.0/17161.61.128.1 to 161.61.255.254161.61.255.25532,766
125161.62.0.0/17161.62.0.1 to 161.62.127.254161.62.127.25532,766
126161.62.128.0/17161.62.128.1 to 161.62.255.254161.62.255.25532,766
127161.63.0.0/17161.63.0.1 to 161.63.127.254161.63.127.25532,766
128161.63.128.0/17161.63.128.1 to 161.63.255.254161.63.255.25532,766

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.