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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.

Network250.64.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
250.64.0.0
Broadcast address
250.79.255.255
First usable
250.64.0.1
Last usable
250.79.255.254
Usable hosts
1,048,574 (1,048,576 less the network and broadcast addresses)
Subnet mask
255.240.0.0
Wildcard mask
0.15.255.255 (Cisco ACLs, OSPF)
Prefix length
/12
Type
Reserved 240.0.0.0/4
Future use; not usable on most systems
Old class
E (reserved)
As numbers
Hex FA400000 · Integer 4198498304 to 4199546879
Reverse DNS zones
64.250.in-addr.arpa
65.250.in-addr.arpa
66.250.in-addr.arpa
67.250.in-addr.arpa
68.250.in-addr.arpa
69.250.in-addr.arpa
70.250.in-addr.arpa
71.250.in-addr.arpa
72.250.in-addr.arpa
73.250.in-addr.arpa
74.250.in-addr.arpa
75.250.in-addr.arpa
76.250.in-addr.arpa
77.250.in-addr.arpa
78.250.in-addr.arpa
79.250.in-addr.arpa
/12 is not on a 8-bit boundary, so it takes 16 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address11111010.01000000.00000000.00000000250.64.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network11111010.01000000.00000000.00000000250.64.0.0
Broadcast11111010.01001111.11111111.11111111250.79.255.255
Split into smaller subnets/19
/13 (2)/14 (4)/15 (8)/16 (16)/17 (32)/18 (64)/19 (128)/20 (256)/21 (512)/22 (1,024)/23 (2,048)/24 (4,096)

250.64.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1250.64.0.0/19250.64.0.1 to 250.64.31.254250.64.31.2558,190
2250.64.32.0/19250.64.32.1 to 250.64.63.254250.64.63.2558,190
3250.64.64.0/19250.64.64.1 to 250.64.95.254250.64.95.2558,190
4250.64.96.0/19250.64.96.1 to 250.64.127.254250.64.127.2558,190
5250.64.128.0/19250.64.128.1 to 250.64.159.254250.64.159.2558,190
6250.64.160.0/19250.64.160.1 to 250.64.191.254250.64.191.2558,190
7250.64.192.0/19250.64.192.1 to 250.64.223.254250.64.223.2558,190
8250.64.224.0/19250.64.224.1 to 250.64.255.254250.64.255.2558,190
9250.65.0.0/19250.65.0.1 to 250.65.31.254250.65.31.2558,190
10250.65.32.0/19250.65.32.1 to 250.65.63.254250.65.63.2558,190
11250.65.64.0/19250.65.64.1 to 250.65.95.254250.65.95.2558,190
12250.65.96.0/19250.65.96.1 to 250.65.127.254250.65.127.2558,190
13250.65.128.0/19250.65.128.1 to 250.65.159.254250.65.159.2558,190
14250.65.160.0/19250.65.160.1 to 250.65.191.254250.65.191.2558,190
15250.65.192.0/19250.65.192.1 to 250.65.223.254250.65.223.2558,190
16250.65.224.0/19250.65.224.1 to 250.65.255.254250.65.255.2558,190
17250.66.0.0/19250.66.0.1 to 250.66.31.254250.66.31.2558,190
18250.66.32.0/19250.66.32.1 to 250.66.63.254250.66.63.2558,190
19250.66.64.0/19250.66.64.1 to 250.66.95.254250.66.95.2558,190
20250.66.96.0/19250.66.96.1 to 250.66.127.254250.66.127.2558,190
21250.66.128.0/19250.66.128.1 to 250.66.159.254250.66.159.2558,190
22250.66.160.0/19250.66.160.1 to 250.66.191.254250.66.191.2558,190
23250.66.192.0/19250.66.192.1 to 250.66.223.254250.66.223.2558,190
24250.66.224.0/19250.66.224.1 to 250.66.255.254250.66.255.2558,190
25250.67.0.0/19250.67.0.1 to 250.67.31.254250.67.31.2558,190
26250.67.32.0/19250.67.32.1 to 250.67.63.254250.67.63.2558,190
27250.67.64.0/19250.67.64.1 to 250.67.95.254250.67.95.2558,190
28250.67.96.0/19250.67.96.1 to 250.67.127.254250.67.127.2558,190
29250.67.128.0/19250.67.128.1 to 250.67.159.254250.67.159.2558,190
30250.67.160.0/19250.67.160.1 to 250.67.191.254250.67.191.2558,190
31250.67.192.0/19250.67.192.1 to 250.67.223.254250.67.223.2558,190
32250.67.224.0/19250.67.224.1 to 250.67.255.254250.67.255.2558,190
33250.68.0.0/19250.68.0.1 to 250.68.31.254250.68.31.2558,190
34250.68.32.0/19250.68.32.1 to 250.68.63.254250.68.63.2558,190
35250.68.64.0/19250.68.64.1 to 250.68.95.254250.68.95.2558,190
36250.68.96.0/19250.68.96.1 to 250.68.127.254250.68.127.2558,190
37250.68.128.0/19250.68.128.1 to 250.68.159.254250.68.159.2558,190
38250.68.160.0/19250.68.160.1 to 250.68.191.254250.68.191.2558,190
39250.68.192.0/19250.68.192.1 to 250.68.223.254250.68.223.2558,190
40250.68.224.0/19250.68.224.1 to 250.68.255.254250.68.255.2558,190
41250.69.0.0/19250.69.0.1 to 250.69.31.254250.69.31.2558,190
42250.69.32.0/19250.69.32.1 to 250.69.63.254250.69.63.2558,190
43250.69.64.0/19250.69.64.1 to 250.69.95.254250.69.95.2558,190
44250.69.96.0/19250.69.96.1 to 250.69.127.254250.69.127.2558,190
45250.69.128.0/19250.69.128.1 to 250.69.159.254250.69.159.2558,190
46250.69.160.0/19250.69.160.1 to 250.69.191.254250.69.191.2558,190
47250.69.192.0/19250.69.192.1 to 250.69.223.254250.69.223.2558,190
48250.69.224.0/19250.69.224.1 to 250.69.255.254250.69.255.2558,190
49250.70.0.0/19250.70.0.1 to 250.70.31.254250.70.31.2558,190
50250.70.32.0/19250.70.32.1 to 250.70.63.254250.70.63.2558,190
51250.70.64.0/19250.70.64.1 to 250.70.95.254250.70.95.2558,190
52250.70.96.0/19250.70.96.1 to 250.70.127.254250.70.127.2558,190
53250.70.128.0/19250.70.128.1 to 250.70.159.254250.70.159.2558,190
54250.70.160.0/19250.70.160.1 to 250.70.191.254250.70.191.2558,190
55250.70.192.0/19250.70.192.1 to 250.70.223.254250.70.223.2558,190
56250.70.224.0/19250.70.224.1 to 250.70.255.254250.70.255.2558,190
57250.71.0.0/19250.71.0.1 to 250.71.31.254250.71.31.2558,190
58250.71.32.0/19250.71.32.1 to 250.71.63.254250.71.63.2558,190
59250.71.64.0/19250.71.64.1 to 250.71.95.254250.71.95.2558,190
60250.71.96.0/19250.71.96.1 to 250.71.127.254250.71.127.2558,190
61250.71.128.0/19250.71.128.1 to 250.71.159.254250.71.159.2558,190
62250.71.160.0/19250.71.160.1 to 250.71.191.254250.71.191.2558,190
63250.71.192.0/19250.71.192.1 to 250.71.223.254250.71.223.2558,190
64250.71.224.0/19250.71.224.1 to 250.71.255.254250.71.255.2558,190
65250.72.0.0/19250.72.0.1 to 250.72.31.254250.72.31.2558,190
66250.72.32.0/19250.72.32.1 to 250.72.63.254250.72.63.2558,190
67250.72.64.0/19250.72.64.1 to 250.72.95.254250.72.95.2558,190
68250.72.96.0/19250.72.96.1 to 250.72.127.254250.72.127.2558,190
69250.72.128.0/19250.72.128.1 to 250.72.159.254250.72.159.2558,190
70250.72.160.0/19250.72.160.1 to 250.72.191.254250.72.191.2558,190
71250.72.192.0/19250.72.192.1 to 250.72.223.254250.72.223.2558,190
72250.72.224.0/19250.72.224.1 to 250.72.255.254250.72.255.2558,190
73250.73.0.0/19250.73.0.1 to 250.73.31.254250.73.31.2558,190
74250.73.32.0/19250.73.32.1 to 250.73.63.254250.73.63.2558,190
75250.73.64.0/19250.73.64.1 to 250.73.95.254250.73.95.2558,190
76250.73.96.0/19250.73.96.1 to 250.73.127.254250.73.127.2558,190
77250.73.128.0/19250.73.128.1 to 250.73.159.254250.73.159.2558,190
78250.73.160.0/19250.73.160.1 to 250.73.191.254250.73.191.2558,190
79250.73.192.0/19250.73.192.1 to 250.73.223.254250.73.223.2558,190
80250.73.224.0/19250.73.224.1 to 250.73.255.254250.73.255.2558,190
81250.74.0.0/19250.74.0.1 to 250.74.31.254250.74.31.2558,190
82250.74.32.0/19250.74.32.1 to 250.74.63.254250.74.63.2558,190
83250.74.64.0/19250.74.64.1 to 250.74.95.254250.74.95.2558,190
84250.74.96.0/19250.74.96.1 to 250.74.127.254250.74.127.2558,190
85250.74.128.0/19250.74.128.1 to 250.74.159.254250.74.159.2558,190
86250.74.160.0/19250.74.160.1 to 250.74.191.254250.74.191.2558,190
87250.74.192.0/19250.74.192.1 to 250.74.223.254250.74.223.2558,190
88250.74.224.0/19250.74.224.1 to 250.74.255.254250.74.255.2558,190
89250.75.0.0/19250.75.0.1 to 250.75.31.254250.75.31.2558,190
90250.75.32.0/19250.75.32.1 to 250.75.63.254250.75.63.2558,190
91250.75.64.0/19250.75.64.1 to 250.75.95.254250.75.95.2558,190
92250.75.96.0/19250.75.96.1 to 250.75.127.254250.75.127.2558,190
93250.75.128.0/19250.75.128.1 to 250.75.159.254250.75.159.2558,190
94250.75.160.0/19250.75.160.1 to 250.75.191.254250.75.191.2558,190
95250.75.192.0/19250.75.192.1 to 250.75.223.254250.75.223.2558,190
96250.75.224.0/19250.75.224.1 to 250.75.255.254250.75.255.2558,190
97250.76.0.0/19250.76.0.1 to 250.76.31.254250.76.31.2558,190
98250.76.32.0/19250.76.32.1 to 250.76.63.254250.76.63.2558,190
99250.76.64.0/19250.76.64.1 to 250.76.95.254250.76.95.2558,190
100250.76.96.0/19250.76.96.1 to 250.76.127.254250.76.127.2558,190
101250.76.128.0/19250.76.128.1 to 250.76.159.254250.76.159.2558,190
102250.76.160.0/19250.76.160.1 to 250.76.191.254250.76.191.2558,190
103250.76.192.0/19250.76.192.1 to 250.76.223.254250.76.223.2558,190
104250.76.224.0/19250.76.224.1 to 250.76.255.254250.76.255.2558,190
105250.77.0.0/19250.77.0.1 to 250.77.31.254250.77.31.2558,190
106250.77.32.0/19250.77.32.1 to 250.77.63.254250.77.63.2558,190
107250.77.64.0/19250.77.64.1 to 250.77.95.254250.77.95.2558,190
108250.77.96.0/19250.77.96.1 to 250.77.127.254250.77.127.2558,190
109250.77.128.0/19250.77.128.1 to 250.77.159.254250.77.159.2558,190
110250.77.160.0/19250.77.160.1 to 250.77.191.254250.77.191.2558,190
111250.77.192.0/19250.77.192.1 to 250.77.223.254250.77.223.2558,190
112250.77.224.0/19250.77.224.1 to 250.77.255.254250.77.255.2558,190
113250.78.0.0/19250.78.0.1 to 250.78.31.254250.78.31.2558,190
114250.78.32.0/19250.78.32.1 to 250.78.63.254250.78.63.2558,190
115250.78.64.0/19250.78.64.1 to 250.78.95.254250.78.95.2558,190
116250.78.96.0/19250.78.96.1 to 250.78.127.254250.78.127.2558,190
117250.78.128.0/19250.78.128.1 to 250.78.159.254250.78.159.2558,190
118250.78.160.0/19250.78.160.1 to 250.78.191.254250.78.191.2558,190
119250.78.192.0/19250.78.192.1 to 250.78.223.254250.78.223.2558,190
120250.78.224.0/19250.78.224.1 to 250.78.255.254250.78.255.2558,190
121250.79.0.0/19250.79.0.1 to 250.79.31.254250.79.31.2558,190
122250.79.32.0/19250.79.32.1 to 250.79.63.254250.79.63.2558,190
123250.79.64.0/19250.79.64.1 to 250.79.95.254250.79.95.2558,190
124250.79.96.0/19250.79.96.1 to 250.79.127.254250.79.127.2558,190
125250.79.128.0/19250.79.128.1 to 250.79.159.254250.79.159.2558,190
126250.79.160.0/19250.79.160.1 to 250.79.191.254250.79.191.2558,190
127250.79.192.0/19250.79.192.1 to 250.79.223.254250.79.223.2558,190
128250.79.224.0/19250.79.224.1 to 250.79.255.254250.79.255.2558,190

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.