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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.

Network242.0.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
242.0.0.0
Broadcast address
242.63.255.255
First usable
242.0.0.1
Last usable
242.63.255.254
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 F2000000 · Integer 4060086272 to 4064280575
Reverse DNS zones
0.242.in-addr.arpa
1.242.in-addr.arpa
2.242.in-addr.arpa
3.242.in-addr.arpa
4.242.in-addr.arpa
5.242.in-addr.arpa
6.242.in-addr.arpa
7.242.in-addr.arpa
8.242.in-addr.arpa
9.242.in-addr.arpa
10.242.in-addr.arpa
11.242.in-addr.arpa
12.242.in-addr.arpa
13.242.in-addr.arpa
14.242.in-addr.arpa
15.242.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
Address11110010.00000000.00000000.00000000242.0.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network11110010.00000000.00000000.00000000242.0.0.0
Broadcast11110010.00111111.11111111.11111111242.63.255.255
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)

242.0.0.0/10 makes 128 subnets of /17.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1242.0.0.0/17242.0.0.1 to 242.0.127.254242.0.127.25532,766
2242.0.128.0/17242.0.128.1 to 242.0.255.254242.0.255.25532,766
3242.1.0.0/17242.1.0.1 to 242.1.127.254242.1.127.25532,766
4242.1.128.0/17242.1.128.1 to 242.1.255.254242.1.255.25532,766
5242.2.0.0/17242.2.0.1 to 242.2.127.254242.2.127.25532,766
6242.2.128.0/17242.2.128.1 to 242.2.255.254242.2.255.25532,766
7242.3.0.0/17242.3.0.1 to 242.3.127.254242.3.127.25532,766
8242.3.128.0/17242.3.128.1 to 242.3.255.254242.3.255.25532,766
9242.4.0.0/17242.4.0.1 to 242.4.127.254242.4.127.25532,766
10242.4.128.0/17242.4.128.1 to 242.4.255.254242.4.255.25532,766
11242.5.0.0/17242.5.0.1 to 242.5.127.254242.5.127.25532,766
12242.5.128.0/17242.5.128.1 to 242.5.255.254242.5.255.25532,766
13242.6.0.0/17242.6.0.1 to 242.6.127.254242.6.127.25532,766
14242.6.128.0/17242.6.128.1 to 242.6.255.254242.6.255.25532,766
15242.7.0.0/17242.7.0.1 to 242.7.127.254242.7.127.25532,766
16242.7.128.0/17242.7.128.1 to 242.7.255.254242.7.255.25532,766
17242.8.0.0/17242.8.0.1 to 242.8.127.254242.8.127.25532,766
18242.8.128.0/17242.8.128.1 to 242.8.255.254242.8.255.25532,766
19242.9.0.0/17242.9.0.1 to 242.9.127.254242.9.127.25532,766
20242.9.128.0/17242.9.128.1 to 242.9.255.254242.9.255.25532,766
21242.10.0.0/17242.10.0.1 to 242.10.127.254242.10.127.25532,766
22242.10.128.0/17242.10.128.1 to 242.10.255.254242.10.255.25532,766
23242.11.0.0/17242.11.0.1 to 242.11.127.254242.11.127.25532,766
24242.11.128.0/17242.11.128.1 to 242.11.255.254242.11.255.25532,766
25242.12.0.0/17242.12.0.1 to 242.12.127.254242.12.127.25532,766
26242.12.128.0/17242.12.128.1 to 242.12.255.254242.12.255.25532,766
27242.13.0.0/17242.13.0.1 to 242.13.127.254242.13.127.25532,766
28242.13.128.0/17242.13.128.1 to 242.13.255.254242.13.255.25532,766
29242.14.0.0/17242.14.0.1 to 242.14.127.254242.14.127.25532,766
30242.14.128.0/17242.14.128.1 to 242.14.255.254242.14.255.25532,766
31242.15.0.0/17242.15.0.1 to 242.15.127.254242.15.127.25532,766
32242.15.128.0/17242.15.128.1 to 242.15.255.254242.15.255.25532,766
33242.16.0.0/17242.16.0.1 to 242.16.127.254242.16.127.25532,766
34242.16.128.0/17242.16.128.1 to 242.16.255.254242.16.255.25532,766
35242.17.0.0/17242.17.0.1 to 242.17.127.254242.17.127.25532,766
36242.17.128.0/17242.17.128.1 to 242.17.255.254242.17.255.25532,766
37242.18.0.0/17242.18.0.1 to 242.18.127.254242.18.127.25532,766
38242.18.128.0/17242.18.128.1 to 242.18.255.254242.18.255.25532,766
39242.19.0.0/17242.19.0.1 to 242.19.127.254242.19.127.25532,766
40242.19.128.0/17242.19.128.1 to 242.19.255.254242.19.255.25532,766
41242.20.0.0/17242.20.0.1 to 242.20.127.254242.20.127.25532,766
42242.20.128.0/17242.20.128.1 to 242.20.255.254242.20.255.25532,766
43242.21.0.0/17242.21.0.1 to 242.21.127.254242.21.127.25532,766
44242.21.128.0/17242.21.128.1 to 242.21.255.254242.21.255.25532,766
45242.22.0.0/17242.22.0.1 to 242.22.127.254242.22.127.25532,766
46242.22.128.0/17242.22.128.1 to 242.22.255.254242.22.255.25532,766
47242.23.0.0/17242.23.0.1 to 242.23.127.254242.23.127.25532,766
48242.23.128.0/17242.23.128.1 to 242.23.255.254242.23.255.25532,766
49242.24.0.0/17242.24.0.1 to 242.24.127.254242.24.127.25532,766
50242.24.128.0/17242.24.128.1 to 242.24.255.254242.24.255.25532,766
51242.25.0.0/17242.25.0.1 to 242.25.127.254242.25.127.25532,766
52242.25.128.0/17242.25.128.1 to 242.25.255.254242.25.255.25532,766
53242.26.0.0/17242.26.0.1 to 242.26.127.254242.26.127.25532,766
54242.26.128.0/17242.26.128.1 to 242.26.255.254242.26.255.25532,766
55242.27.0.0/17242.27.0.1 to 242.27.127.254242.27.127.25532,766
56242.27.128.0/17242.27.128.1 to 242.27.255.254242.27.255.25532,766
57242.28.0.0/17242.28.0.1 to 242.28.127.254242.28.127.25532,766
58242.28.128.0/17242.28.128.1 to 242.28.255.254242.28.255.25532,766
59242.29.0.0/17242.29.0.1 to 242.29.127.254242.29.127.25532,766
60242.29.128.0/17242.29.128.1 to 242.29.255.254242.29.255.25532,766
61242.30.0.0/17242.30.0.1 to 242.30.127.254242.30.127.25532,766
62242.30.128.0/17242.30.128.1 to 242.30.255.254242.30.255.25532,766
63242.31.0.0/17242.31.0.1 to 242.31.127.254242.31.127.25532,766
64242.31.128.0/17242.31.128.1 to 242.31.255.254242.31.255.25532,766
65242.32.0.0/17242.32.0.1 to 242.32.127.254242.32.127.25532,766
66242.32.128.0/17242.32.128.1 to 242.32.255.254242.32.255.25532,766
67242.33.0.0/17242.33.0.1 to 242.33.127.254242.33.127.25532,766
68242.33.128.0/17242.33.128.1 to 242.33.255.254242.33.255.25532,766
69242.34.0.0/17242.34.0.1 to 242.34.127.254242.34.127.25532,766
70242.34.128.0/17242.34.128.1 to 242.34.255.254242.34.255.25532,766
71242.35.0.0/17242.35.0.1 to 242.35.127.254242.35.127.25532,766
72242.35.128.0/17242.35.128.1 to 242.35.255.254242.35.255.25532,766
73242.36.0.0/17242.36.0.1 to 242.36.127.254242.36.127.25532,766
74242.36.128.0/17242.36.128.1 to 242.36.255.254242.36.255.25532,766
75242.37.0.0/17242.37.0.1 to 242.37.127.254242.37.127.25532,766
76242.37.128.0/17242.37.128.1 to 242.37.255.254242.37.255.25532,766
77242.38.0.0/17242.38.0.1 to 242.38.127.254242.38.127.25532,766
78242.38.128.0/17242.38.128.1 to 242.38.255.254242.38.255.25532,766
79242.39.0.0/17242.39.0.1 to 242.39.127.254242.39.127.25532,766
80242.39.128.0/17242.39.128.1 to 242.39.255.254242.39.255.25532,766
81242.40.0.0/17242.40.0.1 to 242.40.127.254242.40.127.25532,766
82242.40.128.0/17242.40.128.1 to 242.40.255.254242.40.255.25532,766
83242.41.0.0/17242.41.0.1 to 242.41.127.254242.41.127.25532,766
84242.41.128.0/17242.41.128.1 to 242.41.255.254242.41.255.25532,766
85242.42.0.0/17242.42.0.1 to 242.42.127.254242.42.127.25532,766
86242.42.128.0/17242.42.128.1 to 242.42.255.254242.42.255.25532,766
87242.43.0.0/17242.43.0.1 to 242.43.127.254242.43.127.25532,766
88242.43.128.0/17242.43.128.1 to 242.43.255.254242.43.255.25532,766
89242.44.0.0/17242.44.0.1 to 242.44.127.254242.44.127.25532,766
90242.44.128.0/17242.44.128.1 to 242.44.255.254242.44.255.25532,766
91242.45.0.0/17242.45.0.1 to 242.45.127.254242.45.127.25532,766
92242.45.128.0/17242.45.128.1 to 242.45.255.254242.45.255.25532,766
93242.46.0.0/17242.46.0.1 to 242.46.127.254242.46.127.25532,766
94242.46.128.0/17242.46.128.1 to 242.46.255.254242.46.255.25532,766
95242.47.0.0/17242.47.0.1 to 242.47.127.254242.47.127.25532,766
96242.47.128.0/17242.47.128.1 to 242.47.255.254242.47.255.25532,766
97242.48.0.0/17242.48.0.1 to 242.48.127.254242.48.127.25532,766
98242.48.128.0/17242.48.128.1 to 242.48.255.254242.48.255.25532,766
99242.49.0.0/17242.49.0.1 to 242.49.127.254242.49.127.25532,766
100242.49.128.0/17242.49.128.1 to 242.49.255.254242.49.255.25532,766
101242.50.0.0/17242.50.0.1 to 242.50.127.254242.50.127.25532,766
102242.50.128.0/17242.50.128.1 to 242.50.255.254242.50.255.25532,766
103242.51.0.0/17242.51.0.1 to 242.51.127.254242.51.127.25532,766
104242.51.128.0/17242.51.128.1 to 242.51.255.254242.51.255.25532,766
105242.52.0.0/17242.52.0.1 to 242.52.127.254242.52.127.25532,766
106242.52.128.0/17242.52.128.1 to 242.52.255.254242.52.255.25532,766
107242.53.0.0/17242.53.0.1 to 242.53.127.254242.53.127.25532,766
108242.53.128.0/17242.53.128.1 to 242.53.255.254242.53.255.25532,766
109242.54.0.0/17242.54.0.1 to 242.54.127.254242.54.127.25532,766
110242.54.128.0/17242.54.128.1 to 242.54.255.254242.54.255.25532,766
111242.55.0.0/17242.55.0.1 to 242.55.127.254242.55.127.25532,766
112242.55.128.0/17242.55.128.1 to 242.55.255.254242.55.255.25532,766
113242.56.0.0/17242.56.0.1 to 242.56.127.254242.56.127.25532,766
114242.56.128.0/17242.56.128.1 to 242.56.255.254242.56.255.25532,766
115242.57.0.0/17242.57.0.1 to 242.57.127.254242.57.127.25532,766
116242.57.128.0/17242.57.128.1 to 242.57.255.254242.57.255.25532,766
117242.58.0.0/17242.58.0.1 to 242.58.127.254242.58.127.25532,766
118242.58.128.0/17242.58.128.1 to 242.58.255.254242.58.255.25532,766
119242.59.0.0/17242.59.0.1 to 242.59.127.254242.59.127.25532,766
120242.59.128.0/17242.59.128.1 to 242.59.255.254242.59.255.25532,766
121242.60.0.0/17242.60.0.1 to 242.60.127.254242.60.127.25532,766
122242.60.128.0/17242.60.128.1 to 242.60.255.254242.60.255.25532,766
123242.61.0.0/17242.61.0.1 to 242.61.127.254242.61.127.25532,766
124242.61.128.0/17242.61.128.1 to 242.61.255.254242.61.255.25532,766
125242.62.0.0/17242.62.0.1 to 242.62.127.254242.62.127.25532,766
126242.62.128.0/17242.62.128.1 to 242.62.255.254242.62.255.25532,766
127242.63.0.0/17242.63.0.1 to 242.63.127.254242.63.127.25532,766
128242.63.128.0/17242.63.128.1 to 242.63.255.254242.63.255.25532,766

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.