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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.

Network205.35.0.0/18
Usable hosts16,382
Subnet mask255.255.192.0
Addresses16,384
Network address
205.35.0.0
Broadcast address
205.35.63.255
First usable
205.35.0.1
Last usable
205.35.63.254
Usable hosts
16,382 (16,384 less the network and broadcast addresses)
Subnet mask
255.255.192.0
Wildcard mask
0.0.63.255 (Cisco ACLs, OSPF)
Prefix length
/18
Type
Public public
Old class
C (default /24)
As numbers
Hex CD230000 · Integer 3441623040 to 3441639423
Reverse DNS zones
0.35.205.in-addr.arpa
1.35.205.in-addr.arpa
2.35.205.in-addr.arpa
3.35.205.in-addr.arpa
4.35.205.in-addr.arpa
5.35.205.in-addr.arpa
6.35.205.in-addr.arpa
7.35.205.in-addr.arpa
8.35.205.in-addr.arpa
9.35.205.in-addr.arpa
10.35.205.in-addr.arpa
11.35.205.in-addr.arpa
12.35.205.in-addr.arpa
13.35.205.in-addr.arpa
14.35.205.in-addr.arpa
15.35.205.in-addr.arpa
and 48 more
/18 is not on a 8-bit boundary, so it takes 64 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11001101.00100011.00000000.00000000205.35.0.0
Subnet mask11111111.11111111.11000000.00000000255.255.192.0
Network11001101.00100011.00000000.00000000205.35.0.0
Broadcast11001101.00100011.00111111.11111111205.35.63.255
Split into smaller subnets/25
/19 (2)/20 (4)/21 (8)/22 (16)/23 (32)/24 (64)/25 (128)/26 (256)/27 (512)/28 (1,024)/29 (2,048)/30 (4,096)

205.35.0.0/18 makes 128 subnets of /25.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1205.35.0.0/25205.35.0.1 to 205.35.0.126205.35.0.127126
2205.35.0.128/25205.35.0.129 to 205.35.0.254205.35.0.255126
3205.35.1.0/25205.35.1.1 to 205.35.1.126205.35.1.127126
4205.35.1.128/25205.35.1.129 to 205.35.1.254205.35.1.255126
5205.35.2.0/25205.35.2.1 to 205.35.2.126205.35.2.127126
6205.35.2.128/25205.35.2.129 to 205.35.2.254205.35.2.255126
7205.35.3.0/25205.35.3.1 to 205.35.3.126205.35.3.127126
8205.35.3.128/25205.35.3.129 to 205.35.3.254205.35.3.255126
9205.35.4.0/25205.35.4.1 to 205.35.4.126205.35.4.127126
10205.35.4.128/25205.35.4.129 to 205.35.4.254205.35.4.255126
11205.35.5.0/25205.35.5.1 to 205.35.5.126205.35.5.127126
12205.35.5.128/25205.35.5.129 to 205.35.5.254205.35.5.255126
13205.35.6.0/25205.35.6.1 to 205.35.6.126205.35.6.127126
14205.35.6.128/25205.35.6.129 to 205.35.6.254205.35.6.255126
15205.35.7.0/25205.35.7.1 to 205.35.7.126205.35.7.127126
16205.35.7.128/25205.35.7.129 to 205.35.7.254205.35.7.255126
17205.35.8.0/25205.35.8.1 to 205.35.8.126205.35.8.127126
18205.35.8.128/25205.35.8.129 to 205.35.8.254205.35.8.255126
19205.35.9.0/25205.35.9.1 to 205.35.9.126205.35.9.127126
20205.35.9.128/25205.35.9.129 to 205.35.9.254205.35.9.255126
21205.35.10.0/25205.35.10.1 to 205.35.10.126205.35.10.127126
22205.35.10.128/25205.35.10.129 to 205.35.10.254205.35.10.255126
23205.35.11.0/25205.35.11.1 to 205.35.11.126205.35.11.127126
24205.35.11.128/25205.35.11.129 to 205.35.11.254205.35.11.255126
25205.35.12.0/25205.35.12.1 to 205.35.12.126205.35.12.127126
26205.35.12.128/25205.35.12.129 to 205.35.12.254205.35.12.255126
27205.35.13.0/25205.35.13.1 to 205.35.13.126205.35.13.127126
28205.35.13.128/25205.35.13.129 to 205.35.13.254205.35.13.255126
29205.35.14.0/25205.35.14.1 to 205.35.14.126205.35.14.127126
30205.35.14.128/25205.35.14.129 to 205.35.14.254205.35.14.255126
31205.35.15.0/25205.35.15.1 to 205.35.15.126205.35.15.127126
32205.35.15.128/25205.35.15.129 to 205.35.15.254205.35.15.255126
33205.35.16.0/25205.35.16.1 to 205.35.16.126205.35.16.127126
34205.35.16.128/25205.35.16.129 to 205.35.16.254205.35.16.255126
35205.35.17.0/25205.35.17.1 to 205.35.17.126205.35.17.127126
36205.35.17.128/25205.35.17.129 to 205.35.17.254205.35.17.255126
37205.35.18.0/25205.35.18.1 to 205.35.18.126205.35.18.127126
38205.35.18.128/25205.35.18.129 to 205.35.18.254205.35.18.255126
39205.35.19.0/25205.35.19.1 to 205.35.19.126205.35.19.127126
40205.35.19.128/25205.35.19.129 to 205.35.19.254205.35.19.255126
41205.35.20.0/25205.35.20.1 to 205.35.20.126205.35.20.127126
42205.35.20.128/25205.35.20.129 to 205.35.20.254205.35.20.255126
43205.35.21.0/25205.35.21.1 to 205.35.21.126205.35.21.127126
44205.35.21.128/25205.35.21.129 to 205.35.21.254205.35.21.255126
45205.35.22.0/25205.35.22.1 to 205.35.22.126205.35.22.127126
46205.35.22.128/25205.35.22.129 to 205.35.22.254205.35.22.255126
47205.35.23.0/25205.35.23.1 to 205.35.23.126205.35.23.127126
48205.35.23.128/25205.35.23.129 to 205.35.23.254205.35.23.255126
49205.35.24.0/25205.35.24.1 to 205.35.24.126205.35.24.127126
50205.35.24.128/25205.35.24.129 to 205.35.24.254205.35.24.255126
51205.35.25.0/25205.35.25.1 to 205.35.25.126205.35.25.127126
52205.35.25.128/25205.35.25.129 to 205.35.25.254205.35.25.255126
53205.35.26.0/25205.35.26.1 to 205.35.26.126205.35.26.127126
54205.35.26.128/25205.35.26.129 to 205.35.26.254205.35.26.255126
55205.35.27.0/25205.35.27.1 to 205.35.27.126205.35.27.127126
56205.35.27.128/25205.35.27.129 to 205.35.27.254205.35.27.255126
57205.35.28.0/25205.35.28.1 to 205.35.28.126205.35.28.127126
58205.35.28.128/25205.35.28.129 to 205.35.28.254205.35.28.255126
59205.35.29.0/25205.35.29.1 to 205.35.29.126205.35.29.127126
60205.35.29.128/25205.35.29.129 to 205.35.29.254205.35.29.255126
61205.35.30.0/25205.35.30.1 to 205.35.30.126205.35.30.127126
62205.35.30.128/25205.35.30.129 to 205.35.30.254205.35.30.255126
63205.35.31.0/25205.35.31.1 to 205.35.31.126205.35.31.127126
64205.35.31.128/25205.35.31.129 to 205.35.31.254205.35.31.255126
65205.35.32.0/25205.35.32.1 to 205.35.32.126205.35.32.127126
66205.35.32.128/25205.35.32.129 to 205.35.32.254205.35.32.255126
67205.35.33.0/25205.35.33.1 to 205.35.33.126205.35.33.127126
68205.35.33.128/25205.35.33.129 to 205.35.33.254205.35.33.255126
69205.35.34.0/25205.35.34.1 to 205.35.34.126205.35.34.127126
70205.35.34.128/25205.35.34.129 to 205.35.34.254205.35.34.255126
71205.35.35.0/25205.35.35.1 to 205.35.35.126205.35.35.127126
72205.35.35.128/25205.35.35.129 to 205.35.35.254205.35.35.255126
73205.35.36.0/25205.35.36.1 to 205.35.36.126205.35.36.127126
74205.35.36.128/25205.35.36.129 to 205.35.36.254205.35.36.255126
75205.35.37.0/25205.35.37.1 to 205.35.37.126205.35.37.127126
76205.35.37.128/25205.35.37.129 to 205.35.37.254205.35.37.255126
77205.35.38.0/25205.35.38.1 to 205.35.38.126205.35.38.127126
78205.35.38.128/25205.35.38.129 to 205.35.38.254205.35.38.255126
79205.35.39.0/25205.35.39.1 to 205.35.39.126205.35.39.127126
80205.35.39.128/25205.35.39.129 to 205.35.39.254205.35.39.255126
81205.35.40.0/25205.35.40.1 to 205.35.40.126205.35.40.127126
82205.35.40.128/25205.35.40.129 to 205.35.40.254205.35.40.255126
83205.35.41.0/25205.35.41.1 to 205.35.41.126205.35.41.127126
84205.35.41.128/25205.35.41.129 to 205.35.41.254205.35.41.255126
85205.35.42.0/25205.35.42.1 to 205.35.42.126205.35.42.127126
86205.35.42.128/25205.35.42.129 to 205.35.42.254205.35.42.255126
87205.35.43.0/25205.35.43.1 to 205.35.43.126205.35.43.127126
88205.35.43.128/25205.35.43.129 to 205.35.43.254205.35.43.255126
89205.35.44.0/25205.35.44.1 to 205.35.44.126205.35.44.127126
90205.35.44.128/25205.35.44.129 to 205.35.44.254205.35.44.255126
91205.35.45.0/25205.35.45.1 to 205.35.45.126205.35.45.127126
92205.35.45.128/25205.35.45.129 to 205.35.45.254205.35.45.255126
93205.35.46.0/25205.35.46.1 to 205.35.46.126205.35.46.127126
94205.35.46.128/25205.35.46.129 to 205.35.46.254205.35.46.255126
95205.35.47.0/25205.35.47.1 to 205.35.47.126205.35.47.127126
96205.35.47.128/25205.35.47.129 to 205.35.47.254205.35.47.255126
97205.35.48.0/25205.35.48.1 to 205.35.48.126205.35.48.127126
98205.35.48.128/25205.35.48.129 to 205.35.48.254205.35.48.255126
99205.35.49.0/25205.35.49.1 to 205.35.49.126205.35.49.127126
100205.35.49.128/25205.35.49.129 to 205.35.49.254205.35.49.255126
101205.35.50.0/25205.35.50.1 to 205.35.50.126205.35.50.127126
102205.35.50.128/25205.35.50.129 to 205.35.50.254205.35.50.255126
103205.35.51.0/25205.35.51.1 to 205.35.51.126205.35.51.127126
104205.35.51.128/25205.35.51.129 to 205.35.51.254205.35.51.255126
105205.35.52.0/25205.35.52.1 to 205.35.52.126205.35.52.127126
106205.35.52.128/25205.35.52.129 to 205.35.52.254205.35.52.255126
107205.35.53.0/25205.35.53.1 to 205.35.53.126205.35.53.127126
108205.35.53.128/25205.35.53.129 to 205.35.53.254205.35.53.255126
109205.35.54.0/25205.35.54.1 to 205.35.54.126205.35.54.127126
110205.35.54.128/25205.35.54.129 to 205.35.54.254205.35.54.255126
111205.35.55.0/25205.35.55.1 to 205.35.55.126205.35.55.127126
112205.35.55.128/25205.35.55.129 to 205.35.55.254205.35.55.255126
113205.35.56.0/25205.35.56.1 to 205.35.56.126205.35.56.127126
114205.35.56.128/25205.35.56.129 to 205.35.56.254205.35.56.255126
115205.35.57.0/25205.35.57.1 to 205.35.57.126205.35.57.127126
116205.35.57.128/25205.35.57.129 to 205.35.57.254205.35.57.255126
117205.35.58.0/25205.35.58.1 to 205.35.58.126205.35.58.127126
118205.35.58.128/25205.35.58.129 to 205.35.58.254205.35.58.255126
119205.35.59.0/25205.35.59.1 to 205.35.59.126205.35.59.127126
120205.35.59.128/25205.35.59.129 to 205.35.59.254205.35.59.255126
121205.35.60.0/25205.35.60.1 to 205.35.60.126205.35.60.127126
122205.35.60.128/25205.35.60.129 to 205.35.60.254205.35.60.255126
123205.35.61.0/25205.35.61.1 to 205.35.61.126205.35.61.127126
124205.35.61.128/25205.35.61.129 to 205.35.61.254205.35.61.255126
125205.35.62.0/25205.35.62.1 to 205.35.62.126205.35.62.127126
126205.35.62.128/25205.35.62.129 to 205.35.62.254205.35.62.255126
127205.35.63.0/25205.35.63.1 to 205.35.63.126205.35.63.127126
128205.35.63.128/25205.35.63.129 to 205.35.63.254205.35.63.255126

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.