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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.

Network210.37.64.0/18
Usable hosts16,382
Subnet mask255.255.192.0
Addresses16,384
Network address
210.37.64.0
Broadcast address
210.37.127.255
First usable
210.37.64.1
Last usable
210.37.127.254
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 D2254000 · Integer 3525656576 to 3525672959
Reverse DNS zones
64.37.210.in-addr.arpa
65.37.210.in-addr.arpa
66.37.210.in-addr.arpa
67.37.210.in-addr.arpa
68.37.210.in-addr.arpa
69.37.210.in-addr.arpa
70.37.210.in-addr.arpa
71.37.210.in-addr.arpa
72.37.210.in-addr.arpa
73.37.210.in-addr.arpa
74.37.210.in-addr.arpa
75.37.210.in-addr.arpa
76.37.210.in-addr.arpa
77.37.210.in-addr.arpa
78.37.210.in-addr.arpa
79.37.210.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
Address11010010.00100101.01000000.00000000210.37.64.0
Subnet mask11111111.11111111.11000000.00000000255.255.192.0
Network11010010.00100101.01000000.00000000210.37.64.0
Broadcast11010010.00100101.01111111.11111111210.37.127.255
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)

210.37.64.0/18 makes 128 subnets of /25.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1210.37.64.0/25210.37.64.1 to 210.37.64.126210.37.64.127126
2210.37.64.128/25210.37.64.129 to 210.37.64.254210.37.64.255126
3210.37.65.0/25210.37.65.1 to 210.37.65.126210.37.65.127126
4210.37.65.128/25210.37.65.129 to 210.37.65.254210.37.65.255126
5210.37.66.0/25210.37.66.1 to 210.37.66.126210.37.66.127126
6210.37.66.128/25210.37.66.129 to 210.37.66.254210.37.66.255126
7210.37.67.0/25210.37.67.1 to 210.37.67.126210.37.67.127126
8210.37.67.128/25210.37.67.129 to 210.37.67.254210.37.67.255126
9210.37.68.0/25210.37.68.1 to 210.37.68.126210.37.68.127126
10210.37.68.128/25210.37.68.129 to 210.37.68.254210.37.68.255126
11210.37.69.0/25210.37.69.1 to 210.37.69.126210.37.69.127126
12210.37.69.128/25210.37.69.129 to 210.37.69.254210.37.69.255126
13210.37.70.0/25210.37.70.1 to 210.37.70.126210.37.70.127126
14210.37.70.128/25210.37.70.129 to 210.37.70.254210.37.70.255126
15210.37.71.0/25210.37.71.1 to 210.37.71.126210.37.71.127126
16210.37.71.128/25210.37.71.129 to 210.37.71.254210.37.71.255126
17210.37.72.0/25210.37.72.1 to 210.37.72.126210.37.72.127126
18210.37.72.128/25210.37.72.129 to 210.37.72.254210.37.72.255126
19210.37.73.0/25210.37.73.1 to 210.37.73.126210.37.73.127126
20210.37.73.128/25210.37.73.129 to 210.37.73.254210.37.73.255126
21210.37.74.0/25210.37.74.1 to 210.37.74.126210.37.74.127126
22210.37.74.128/25210.37.74.129 to 210.37.74.254210.37.74.255126
23210.37.75.0/25210.37.75.1 to 210.37.75.126210.37.75.127126
24210.37.75.128/25210.37.75.129 to 210.37.75.254210.37.75.255126
25210.37.76.0/25210.37.76.1 to 210.37.76.126210.37.76.127126
26210.37.76.128/25210.37.76.129 to 210.37.76.254210.37.76.255126
27210.37.77.0/25210.37.77.1 to 210.37.77.126210.37.77.127126
28210.37.77.128/25210.37.77.129 to 210.37.77.254210.37.77.255126
29210.37.78.0/25210.37.78.1 to 210.37.78.126210.37.78.127126
30210.37.78.128/25210.37.78.129 to 210.37.78.254210.37.78.255126
31210.37.79.0/25210.37.79.1 to 210.37.79.126210.37.79.127126
32210.37.79.128/25210.37.79.129 to 210.37.79.254210.37.79.255126
33210.37.80.0/25210.37.80.1 to 210.37.80.126210.37.80.127126
34210.37.80.128/25210.37.80.129 to 210.37.80.254210.37.80.255126
35210.37.81.0/25210.37.81.1 to 210.37.81.126210.37.81.127126
36210.37.81.128/25210.37.81.129 to 210.37.81.254210.37.81.255126
37210.37.82.0/25210.37.82.1 to 210.37.82.126210.37.82.127126
38210.37.82.128/25210.37.82.129 to 210.37.82.254210.37.82.255126
39210.37.83.0/25210.37.83.1 to 210.37.83.126210.37.83.127126
40210.37.83.128/25210.37.83.129 to 210.37.83.254210.37.83.255126
41210.37.84.0/25210.37.84.1 to 210.37.84.126210.37.84.127126
42210.37.84.128/25210.37.84.129 to 210.37.84.254210.37.84.255126
43210.37.85.0/25210.37.85.1 to 210.37.85.126210.37.85.127126
44210.37.85.128/25210.37.85.129 to 210.37.85.254210.37.85.255126
45210.37.86.0/25210.37.86.1 to 210.37.86.126210.37.86.127126
46210.37.86.128/25210.37.86.129 to 210.37.86.254210.37.86.255126
47210.37.87.0/25210.37.87.1 to 210.37.87.126210.37.87.127126
48210.37.87.128/25210.37.87.129 to 210.37.87.254210.37.87.255126
49210.37.88.0/25210.37.88.1 to 210.37.88.126210.37.88.127126
50210.37.88.128/25210.37.88.129 to 210.37.88.254210.37.88.255126
51210.37.89.0/25210.37.89.1 to 210.37.89.126210.37.89.127126
52210.37.89.128/25210.37.89.129 to 210.37.89.254210.37.89.255126
53210.37.90.0/25210.37.90.1 to 210.37.90.126210.37.90.127126
54210.37.90.128/25210.37.90.129 to 210.37.90.254210.37.90.255126
55210.37.91.0/25210.37.91.1 to 210.37.91.126210.37.91.127126
56210.37.91.128/25210.37.91.129 to 210.37.91.254210.37.91.255126
57210.37.92.0/25210.37.92.1 to 210.37.92.126210.37.92.127126
58210.37.92.128/25210.37.92.129 to 210.37.92.254210.37.92.255126
59210.37.93.0/25210.37.93.1 to 210.37.93.126210.37.93.127126
60210.37.93.128/25210.37.93.129 to 210.37.93.254210.37.93.255126
61210.37.94.0/25210.37.94.1 to 210.37.94.126210.37.94.127126
62210.37.94.128/25210.37.94.129 to 210.37.94.254210.37.94.255126
63210.37.95.0/25210.37.95.1 to 210.37.95.126210.37.95.127126
64210.37.95.128/25210.37.95.129 to 210.37.95.254210.37.95.255126
65210.37.96.0/25210.37.96.1 to 210.37.96.126210.37.96.127126
66210.37.96.128/25210.37.96.129 to 210.37.96.254210.37.96.255126
67210.37.97.0/25210.37.97.1 to 210.37.97.126210.37.97.127126
68210.37.97.128/25210.37.97.129 to 210.37.97.254210.37.97.255126
69210.37.98.0/25210.37.98.1 to 210.37.98.126210.37.98.127126
70210.37.98.128/25210.37.98.129 to 210.37.98.254210.37.98.255126
71210.37.99.0/25210.37.99.1 to 210.37.99.126210.37.99.127126
72210.37.99.128/25210.37.99.129 to 210.37.99.254210.37.99.255126
73210.37.100.0/25210.37.100.1 to 210.37.100.126210.37.100.127126
74210.37.100.128/25210.37.100.129 to 210.37.100.254210.37.100.255126
75210.37.101.0/25210.37.101.1 to 210.37.101.126210.37.101.127126
76210.37.101.128/25210.37.101.129 to 210.37.101.254210.37.101.255126
77210.37.102.0/25210.37.102.1 to 210.37.102.126210.37.102.127126
78210.37.102.128/25210.37.102.129 to 210.37.102.254210.37.102.255126
79210.37.103.0/25210.37.103.1 to 210.37.103.126210.37.103.127126
80210.37.103.128/25210.37.103.129 to 210.37.103.254210.37.103.255126
81210.37.104.0/25210.37.104.1 to 210.37.104.126210.37.104.127126
82210.37.104.128/25210.37.104.129 to 210.37.104.254210.37.104.255126
83210.37.105.0/25210.37.105.1 to 210.37.105.126210.37.105.127126
84210.37.105.128/25210.37.105.129 to 210.37.105.254210.37.105.255126
85210.37.106.0/25210.37.106.1 to 210.37.106.126210.37.106.127126
86210.37.106.128/25210.37.106.129 to 210.37.106.254210.37.106.255126
87210.37.107.0/25210.37.107.1 to 210.37.107.126210.37.107.127126
88210.37.107.128/25210.37.107.129 to 210.37.107.254210.37.107.255126
89210.37.108.0/25210.37.108.1 to 210.37.108.126210.37.108.127126
90210.37.108.128/25210.37.108.129 to 210.37.108.254210.37.108.255126
91210.37.109.0/25210.37.109.1 to 210.37.109.126210.37.109.127126
92210.37.109.128/25210.37.109.129 to 210.37.109.254210.37.109.255126
93210.37.110.0/25210.37.110.1 to 210.37.110.126210.37.110.127126
94210.37.110.128/25210.37.110.129 to 210.37.110.254210.37.110.255126
95210.37.111.0/25210.37.111.1 to 210.37.111.126210.37.111.127126
96210.37.111.128/25210.37.111.129 to 210.37.111.254210.37.111.255126
97210.37.112.0/25210.37.112.1 to 210.37.112.126210.37.112.127126
98210.37.112.128/25210.37.112.129 to 210.37.112.254210.37.112.255126
99210.37.113.0/25210.37.113.1 to 210.37.113.126210.37.113.127126
100210.37.113.128/25210.37.113.129 to 210.37.113.254210.37.113.255126
101210.37.114.0/25210.37.114.1 to 210.37.114.126210.37.114.127126
102210.37.114.128/25210.37.114.129 to 210.37.114.254210.37.114.255126
103210.37.115.0/25210.37.115.1 to 210.37.115.126210.37.115.127126
104210.37.115.128/25210.37.115.129 to 210.37.115.254210.37.115.255126
105210.37.116.0/25210.37.116.1 to 210.37.116.126210.37.116.127126
106210.37.116.128/25210.37.116.129 to 210.37.116.254210.37.116.255126
107210.37.117.0/25210.37.117.1 to 210.37.117.126210.37.117.127126
108210.37.117.128/25210.37.117.129 to 210.37.117.254210.37.117.255126
109210.37.118.0/25210.37.118.1 to 210.37.118.126210.37.118.127126
110210.37.118.128/25210.37.118.129 to 210.37.118.254210.37.118.255126
111210.37.119.0/25210.37.119.1 to 210.37.119.126210.37.119.127126
112210.37.119.128/25210.37.119.129 to 210.37.119.254210.37.119.255126
113210.37.120.0/25210.37.120.1 to 210.37.120.126210.37.120.127126
114210.37.120.128/25210.37.120.129 to 210.37.120.254210.37.120.255126
115210.37.121.0/25210.37.121.1 to 210.37.121.126210.37.121.127126
116210.37.121.128/25210.37.121.129 to 210.37.121.254210.37.121.255126
117210.37.122.0/25210.37.122.1 to 210.37.122.126210.37.122.127126
118210.37.122.128/25210.37.122.129 to 210.37.122.254210.37.122.255126
119210.37.123.0/25210.37.123.1 to 210.37.123.126210.37.123.127126
120210.37.123.128/25210.37.123.129 to 210.37.123.254210.37.123.255126
121210.37.124.0/25210.37.124.1 to 210.37.124.126210.37.124.127126
122210.37.124.128/25210.37.124.129 to 210.37.124.254210.37.124.255126
123210.37.125.0/25210.37.125.1 to 210.37.125.126210.37.125.127126
124210.37.125.128/25210.37.125.129 to 210.37.125.254210.37.125.255126
125210.37.126.0/25210.37.126.1 to 210.37.126.126210.37.126.127126
126210.37.126.128/25210.37.126.129 to 210.37.126.254210.37.126.255126
127210.37.127.0/25210.37.127.1 to 210.37.127.126210.37.127.127126
128210.37.127.128/25210.37.127.129 to 210.37.127.254210.37.127.255126

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.