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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.

Network237.64.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
237.64.0.0
Broadcast address
237.127.255.255
First usable
237.64.0.1
Last usable
237.127.255.254
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
Multicast 224.0.0.0/4
One-to-many traffic, such as IPTV and routing protocols
Old class
D (multicast)
As numbers
Hex ED400000 · Integer 3980394496 to 3984588799
Reverse DNS zones
64.237.in-addr.arpa
65.237.in-addr.arpa
66.237.in-addr.arpa
67.237.in-addr.arpa
68.237.in-addr.arpa
69.237.in-addr.arpa
70.237.in-addr.arpa
71.237.in-addr.arpa
72.237.in-addr.arpa
73.237.in-addr.arpa
74.237.in-addr.arpa
75.237.in-addr.arpa
76.237.in-addr.arpa
77.237.in-addr.arpa
78.237.in-addr.arpa
79.237.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
Address11101101.01000000.00000000.00000000237.64.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network11101101.01000000.00000000.00000000237.64.0.0
Broadcast11101101.01111111.11111111.11111111237.127.255.255
Split into smaller subnets/16
/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)

237.64.0.0/10 makes 64 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1237.64.0.0/16237.64.0.1 to 237.64.255.254237.64.255.25565,534
2237.65.0.0/16237.65.0.1 to 237.65.255.254237.65.255.25565,534
3237.66.0.0/16237.66.0.1 to 237.66.255.254237.66.255.25565,534
4237.67.0.0/16237.67.0.1 to 237.67.255.254237.67.255.25565,534
5237.68.0.0/16237.68.0.1 to 237.68.255.254237.68.255.25565,534
6237.69.0.0/16237.69.0.1 to 237.69.255.254237.69.255.25565,534
7237.70.0.0/16237.70.0.1 to 237.70.255.254237.70.255.25565,534
8237.71.0.0/16237.71.0.1 to 237.71.255.254237.71.255.25565,534
9237.72.0.0/16237.72.0.1 to 237.72.255.254237.72.255.25565,534
10237.73.0.0/16237.73.0.1 to 237.73.255.254237.73.255.25565,534
11237.74.0.0/16237.74.0.1 to 237.74.255.254237.74.255.25565,534
12237.75.0.0/16237.75.0.1 to 237.75.255.254237.75.255.25565,534
13237.76.0.0/16237.76.0.1 to 237.76.255.254237.76.255.25565,534
14237.77.0.0/16237.77.0.1 to 237.77.255.254237.77.255.25565,534
15237.78.0.0/16237.78.0.1 to 237.78.255.254237.78.255.25565,534
16237.79.0.0/16237.79.0.1 to 237.79.255.254237.79.255.25565,534
17237.80.0.0/16237.80.0.1 to 237.80.255.254237.80.255.25565,534
18237.81.0.0/16237.81.0.1 to 237.81.255.254237.81.255.25565,534
19237.82.0.0/16237.82.0.1 to 237.82.255.254237.82.255.25565,534
20237.83.0.0/16237.83.0.1 to 237.83.255.254237.83.255.25565,534
21237.84.0.0/16237.84.0.1 to 237.84.255.254237.84.255.25565,534
22237.85.0.0/16237.85.0.1 to 237.85.255.254237.85.255.25565,534
23237.86.0.0/16237.86.0.1 to 237.86.255.254237.86.255.25565,534
24237.87.0.0/16237.87.0.1 to 237.87.255.254237.87.255.25565,534
25237.88.0.0/16237.88.0.1 to 237.88.255.254237.88.255.25565,534
26237.89.0.0/16237.89.0.1 to 237.89.255.254237.89.255.25565,534
27237.90.0.0/16237.90.0.1 to 237.90.255.254237.90.255.25565,534
28237.91.0.0/16237.91.0.1 to 237.91.255.254237.91.255.25565,534
29237.92.0.0/16237.92.0.1 to 237.92.255.254237.92.255.25565,534
30237.93.0.0/16237.93.0.1 to 237.93.255.254237.93.255.25565,534
31237.94.0.0/16237.94.0.1 to 237.94.255.254237.94.255.25565,534
32237.95.0.0/16237.95.0.1 to 237.95.255.254237.95.255.25565,534
33237.96.0.0/16237.96.0.1 to 237.96.255.254237.96.255.25565,534
34237.97.0.0/16237.97.0.1 to 237.97.255.254237.97.255.25565,534
35237.98.0.0/16237.98.0.1 to 237.98.255.254237.98.255.25565,534
36237.99.0.0/16237.99.0.1 to 237.99.255.254237.99.255.25565,534
37237.100.0.0/16237.100.0.1 to 237.100.255.254237.100.255.25565,534
38237.101.0.0/16237.101.0.1 to 237.101.255.254237.101.255.25565,534
39237.102.0.0/16237.102.0.1 to 237.102.255.254237.102.255.25565,534
40237.103.0.0/16237.103.0.1 to 237.103.255.254237.103.255.25565,534
41237.104.0.0/16237.104.0.1 to 237.104.255.254237.104.255.25565,534
42237.105.0.0/16237.105.0.1 to 237.105.255.254237.105.255.25565,534
43237.106.0.0/16237.106.0.1 to 237.106.255.254237.106.255.25565,534
44237.107.0.0/16237.107.0.1 to 237.107.255.254237.107.255.25565,534
45237.108.0.0/16237.108.0.1 to 237.108.255.254237.108.255.25565,534
46237.109.0.0/16237.109.0.1 to 237.109.255.254237.109.255.25565,534
47237.110.0.0/16237.110.0.1 to 237.110.255.254237.110.255.25565,534
48237.111.0.0/16237.111.0.1 to 237.111.255.254237.111.255.25565,534
49237.112.0.0/16237.112.0.1 to 237.112.255.254237.112.255.25565,534
50237.113.0.0/16237.113.0.1 to 237.113.255.254237.113.255.25565,534
51237.114.0.0/16237.114.0.1 to 237.114.255.254237.114.255.25565,534
52237.115.0.0/16237.115.0.1 to 237.115.255.254237.115.255.25565,534
53237.116.0.0/16237.116.0.1 to 237.116.255.254237.116.255.25565,534
54237.117.0.0/16237.117.0.1 to 237.117.255.254237.117.255.25565,534
55237.118.0.0/16237.118.0.1 to 237.118.255.254237.118.255.25565,534
56237.119.0.0/16237.119.0.1 to 237.119.255.254237.119.255.25565,534
57237.120.0.0/16237.120.0.1 to 237.120.255.254237.120.255.25565,534
58237.121.0.0/16237.121.0.1 to 237.121.255.254237.121.255.25565,534
59237.122.0.0/16237.122.0.1 to 237.122.255.254237.122.255.25565,534
60237.123.0.0/16237.123.0.1 to 237.123.255.254237.123.255.25565,534
61237.124.0.0/16237.124.0.1 to 237.124.255.254237.124.255.25565,534
62237.125.0.0/16237.125.0.1 to 237.125.255.254237.125.255.25565,534
63237.126.0.0/16237.126.0.1 to 237.126.255.254237.126.255.25565,534
64237.127.0.0/16237.127.0.1 to 237.127.255.254237.127.255.25565,534

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.