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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.

Network245.0.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
245.0.0.0
Broadcast address
245.63.255.255
First usable
245.0.0.1
Last usable
245.63.255.254
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
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex F5000000 · Integer 4110417920 to 4114612223
Reverse DNS zones
0.245.in-addr.arpa
1.245.in-addr.arpa
2.245.in-addr.arpa
3.245.in-addr.arpa
4.245.in-addr.arpa
5.245.in-addr.arpa
6.245.in-addr.arpa
7.245.in-addr.arpa
8.245.in-addr.arpa
9.245.in-addr.arpa
10.245.in-addr.arpa
11.245.in-addr.arpa
12.245.in-addr.arpa
13.245.in-addr.arpa
14.245.in-addr.arpa
15.245.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
Address11110101.00000000.00000000.00000000245.0.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network11110101.00000000.00000000.00000000245.0.0.0
Broadcast11110101.00111111.11111111.11111111245.63.255.255
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)

245.0.0.0/10 makes 64 subnets of /16.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1245.0.0.0/16245.0.0.1 to 245.0.255.254245.0.255.25565,534
2245.1.0.0/16245.1.0.1 to 245.1.255.254245.1.255.25565,534
3245.2.0.0/16245.2.0.1 to 245.2.255.254245.2.255.25565,534
4245.3.0.0/16245.3.0.1 to 245.3.255.254245.3.255.25565,534
5245.4.0.0/16245.4.0.1 to 245.4.255.254245.4.255.25565,534
6245.5.0.0/16245.5.0.1 to 245.5.255.254245.5.255.25565,534
7245.6.0.0/16245.6.0.1 to 245.6.255.254245.6.255.25565,534
8245.7.0.0/16245.7.0.1 to 245.7.255.254245.7.255.25565,534
9245.8.0.0/16245.8.0.1 to 245.8.255.254245.8.255.25565,534
10245.9.0.0/16245.9.0.1 to 245.9.255.254245.9.255.25565,534
11245.10.0.0/16245.10.0.1 to 245.10.255.254245.10.255.25565,534
12245.11.0.0/16245.11.0.1 to 245.11.255.254245.11.255.25565,534
13245.12.0.0/16245.12.0.1 to 245.12.255.254245.12.255.25565,534
14245.13.0.0/16245.13.0.1 to 245.13.255.254245.13.255.25565,534
15245.14.0.0/16245.14.0.1 to 245.14.255.254245.14.255.25565,534
16245.15.0.0/16245.15.0.1 to 245.15.255.254245.15.255.25565,534
17245.16.0.0/16245.16.0.1 to 245.16.255.254245.16.255.25565,534
18245.17.0.0/16245.17.0.1 to 245.17.255.254245.17.255.25565,534
19245.18.0.0/16245.18.0.1 to 245.18.255.254245.18.255.25565,534
20245.19.0.0/16245.19.0.1 to 245.19.255.254245.19.255.25565,534
21245.20.0.0/16245.20.0.1 to 245.20.255.254245.20.255.25565,534
22245.21.0.0/16245.21.0.1 to 245.21.255.254245.21.255.25565,534
23245.22.0.0/16245.22.0.1 to 245.22.255.254245.22.255.25565,534
24245.23.0.0/16245.23.0.1 to 245.23.255.254245.23.255.25565,534
25245.24.0.0/16245.24.0.1 to 245.24.255.254245.24.255.25565,534
26245.25.0.0/16245.25.0.1 to 245.25.255.254245.25.255.25565,534
27245.26.0.0/16245.26.0.1 to 245.26.255.254245.26.255.25565,534
28245.27.0.0/16245.27.0.1 to 245.27.255.254245.27.255.25565,534
29245.28.0.0/16245.28.0.1 to 245.28.255.254245.28.255.25565,534
30245.29.0.0/16245.29.0.1 to 245.29.255.254245.29.255.25565,534
31245.30.0.0/16245.30.0.1 to 245.30.255.254245.30.255.25565,534
32245.31.0.0/16245.31.0.1 to 245.31.255.254245.31.255.25565,534
33245.32.0.0/16245.32.0.1 to 245.32.255.254245.32.255.25565,534
34245.33.0.0/16245.33.0.1 to 245.33.255.254245.33.255.25565,534
35245.34.0.0/16245.34.0.1 to 245.34.255.254245.34.255.25565,534
36245.35.0.0/16245.35.0.1 to 245.35.255.254245.35.255.25565,534
37245.36.0.0/16245.36.0.1 to 245.36.255.254245.36.255.25565,534
38245.37.0.0/16245.37.0.1 to 245.37.255.254245.37.255.25565,534
39245.38.0.0/16245.38.0.1 to 245.38.255.254245.38.255.25565,534
40245.39.0.0/16245.39.0.1 to 245.39.255.254245.39.255.25565,534
41245.40.0.0/16245.40.0.1 to 245.40.255.254245.40.255.25565,534
42245.41.0.0/16245.41.0.1 to 245.41.255.254245.41.255.25565,534
43245.42.0.0/16245.42.0.1 to 245.42.255.254245.42.255.25565,534
44245.43.0.0/16245.43.0.1 to 245.43.255.254245.43.255.25565,534
45245.44.0.0/16245.44.0.1 to 245.44.255.254245.44.255.25565,534
46245.45.0.0/16245.45.0.1 to 245.45.255.254245.45.255.25565,534
47245.46.0.0/16245.46.0.1 to 245.46.255.254245.46.255.25565,534
48245.47.0.0/16245.47.0.1 to 245.47.255.254245.47.255.25565,534
49245.48.0.0/16245.48.0.1 to 245.48.255.254245.48.255.25565,534
50245.49.0.0/16245.49.0.1 to 245.49.255.254245.49.255.25565,534
51245.50.0.0/16245.50.0.1 to 245.50.255.254245.50.255.25565,534
52245.51.0.0/16245.51.0.1 to 245.51.255.254245.51.255.25565,534
53245.52.0.0/16245.52.0.1 to 245.52.255.254245.52.255.25565,534
54245.53.0.0/16245.53.0.1 to 245.53.255.254245.53.255.25565,534
55245.54.0.0/16245.54.0.1 to 245.54.255.254245.54.255.25565,534
56245.55.0.0/16245.55.0.1 to 245.55.255.254245.55.255.25565,534
57245.56.0.0/16245.56.0.1 to 245.56.255.254245.56.255.25565,534
58245.57.0.0/16245.57.0.1 to 245.57.255.254245.57.255.25565,534
59245.58.0.0/16245.58.0.1 to 245.58.255.254245.58.255.25565,534
60245.59.0.0/16245.59.0.1 to 245.59.255.254245.59.255.25565,534
61245.60.0.0/16245.60.0.1 to 245.60.255.254245.60.255.25565,534
62245.61.0.0/16245.61.0.1 to 245.61.255.254245.61.255.25565,534
63245.62.0.0/16245.62.0.1 to 245.62.255.254245.62.255.25565,534
64245.63.0.0/16245.63.0.1 to 245.63.255.254245.63.255.25565,534

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.