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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.

Network128.0.0.0/3
Usable hosts536,870,910
Subnet mask224.0.0.0
Addresses536,870,912
Network address
128.0.0.0
Broadcast address
159.255.255.255
First usable
128.0.0.1
Last usable
159.255.255.254
Usable hosts
536,870,910 (536,870,912 less the network and broadcast addresses)
Subnet mask
224.0.0.0
Wildcard mask
31.255.255.255 (Cisco ACLs, OSPF)
Prefix length
/3
Type
Public public
Old class
B (default /16)
As numbers
Hex 80000000 · Integer 2147483648 to 2684354559
Reverse DNS zones
128.in-addr.arpa
129.in-addr.arpa
130.in-addr.arpa
131.in-addr.arpa
132.in-addr.arpa
133.in-addr.arpa
134.in-addr.arpa
135.in-addr.arpa
136.in-addr.arpa
137.in-addr.arpa
138.in-addr.arpa
139.in-addr.arpa
140.in-addr.arpa
141.in-addr.arpa
142.in-addr.arpa
143.in-addr.arpa
and 16 more
/3 is not on a 8-bit boundary, so it takes 32 /8 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10000000.00000000.00000000.00000000128.0.0.0
Subnet mask11100000.00000000.00000000.00000000224.0.0.0
Network10000000.00000000.00000000.00000000128.0.0.0
Broadcast10011111.11111111.11111111.11111111159.255.255.255
Split into smaller subnets/10
/4 (2)/5 (4)/6 (8)/7 (16)/8 (32)/9 (64)/10 (128)/11 (256)/12 (512)/13 (1,024)/14 (2,048)/15 (4,096)

128.0.0.0/3 makes 128 subnets of /10.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1128.0.0.0/10128.0.0.1 to 128.63.255.254128.63.255.2554,194,302
2128.64.0.0/10128.64.0.1 to 128.127.255.254128.127.255.2554,194,302
3128.128.0.0/10128.128.0.1 to 128.191.255.254128.191.255.2554,194,302
4128.192.0.0/10128.192.0.1 to 128.255.255.254128.255.255.2554,194,302
5129.0.0.0/10129.0.0.1 to 129.63.255.254129.63.255.2554,194,302
6129.64.0.0/10129.64.0.1 to 129.127.255.254129.127.255.2554,194,302
7129.128.0.0/10129.128.0.1 to 129.191.255.254129.191.255.2554,194,302
8129.192.0.0/10129.192.0.1 to 129.255.255.254129.255.255.2554,194,302
9130.0.0.0/10130.0.0.1 to 130.63.255.254130.63.255.2554,194,302
10130.64.0.0/10130.64.0.1 to 130.127.255.254130.127.255.2554,194,302
11130.128.0.0/10130.128.0.1 to 130.191.255.254130.191.255.2554,194,302
12130.192.0.0/10130.192.0.1 to 130.255.255.254130.255.255.2554,194,302
13131.0.0.0/10131.0.0.1 to 131.63.255.254131.63.255.2554,194,302
14131.64.0.0/10131.64.0.1 to 131.127.255.254131.127.255.2554,194,302
15131.128.0.0/10131.128.0.1 to 131.191.255.254131.191.255.2554,194,302
16131.192.0.0/10131.192.0.1 to 131.255.255.254131.255.255.2554,194,302
17132.0.0.0/10132.0.0.1 to 132.63.255.254132.63.255.2554,194,302
18132.64.0.0/10132.64.0.1 to 132.127.255.254132.127.255.2554,194,302
19132.128.0.0/10132.128.0.1 to 132.191.255.254132.191.255.2554,194,302
20132.192.0.0/10132.192.0.1 to 132.255.255.254132.255.255.2554,194,302
21133.0.0.0/10133.0.0.1 to 133.63.255.254133.63.255.2554,194,302
22133.64.0.0/10133.64.0.1 to 133.127.255.254133.127.255.2554,194,302
23133.128.0.0/10133.128.0.1 to 133.191.255.254133.191.255.2554,194,302
24133.192.0.0/10133.192.0.1 to 133.255.255.254133.255.255.2554,194,302
25134.0.0.0/10134.0.0.1 to 134.63.255.254134.63.255.2554,194,302
26134.64.0.0/10134.64.0.1 to 134.127.255.254134.127.255.2554,194,302
27134.128.0.0/10134.128.0.1 to 134.191.255.254134.191.255.2554,194,302
28134.192.0.0/10134.192.0.1 to 134.255.255.254134.255.255.2554,194,302
29135.0.0.0/10135.0.0.1 to 135.63.255.254135.63.255.2554,194,302
30135.64.0.0/10135.64.0.1 to 135.127.255.254135.127.255.2554,194,302
31135.128.0.0/10135.128.0.1 to 135.191.255.254135.191.255.2554,194,302
32135.192.0.0/10135.192.0.1 to 135.255.255.254135.255.255.2554,194,302
33136.0.0.0/10136.0.0.1 to 136.63.255.254136.63.255.2554,194,302
34136.64.0.0/10136.64.0.1 to 136.127.255.254136.127.255.2554,194,302
35136.128.0.0/10136.128.0.1 to 136.191.255.254136.191.255.2554,194,302
36136.192.0.0/10136.192.0.1 to 136.255.255.254136.255.255.2554,194,302
37137.0.0.0/10137.0.0.1 to 137.63.255.254137.63.255.2554,194,302
38137.64.0.0/10137.64.0.1 to 137.127.255.254137.127.255.2554,194,302
39137.128.0.0/10137.128.0.1 to 137.191.255.254137.191.255.2554,194,302
40137.192.0.0/10137.192.0.1 to 137.255.255.254137.255.255.2554,194,302
41138.0.0.0/10138.0.0.1 to 138.63.255.254138.63.255.2554,194,302
42138.64.0.0/10138.64.0.1 to 138.127.255.254138.127.255.2554,194,302
43138.128.0.0/10138.128.0.1 to 138.191.255.254138.191.255.2554,194,302
44138.192.0.0/10138.192.0.1 to 138.255.255.254138.255.255.2554,194,302
45139.0.0.0/10139.0.0.1 to 139.63.255.254139.63.255.2554,194,302
46139.64.0.0/10139.64.0.1 to 139.127.255.254139.127.255.2554,194,302
47139.128.0.0/10139.128.0.1 to 139.191.255.254139.191.255.2554,194,302
48139.192.0.0/10139.192.0.1 to 139.255.255.254139.255.255.2554,194,302
49140.0.0.0/10140.0.0.1 to 140.63.255.254140.63.255.2554,194,302
50140.64.0.0/10140.64.0.1 to 140.127.255.254140.127.255.2554,194,302
51140.128.0.0/10140.128.0.1 to 140.191.255.254140.191.255.2554,194,302
52140.192.0.0/10140.192.0.1 to 140.255.255.254140.255.255.2554,194,302
53141.0.0.0/10141.0.0.1 to 141.63.255.254141.63.255.2554,194,302
54141.64.0.0/10141.64.0.1 to 141.127.255.254141.127.255.2554,194,302
55141.128.0.0/10141.128.0.1 to 141.191.255.254141.191.255.2554,194,302
56141.192.0.0/10141.192.0.1 to 141.255.255.254141.255.255.2554,194,302
57142.0.0.0/10142.0.0.1 to 142.63.255.254142.63.255.2554,194,302
58142.64.0.0/10142.64.0.1 to 142.127.255.254142.127.255.2554,194,302
59142.128.0.0/10142.128.0.1 to 142.191.255.254142.191.255.2554,194,302
60142.192.0.0/10142.192.0.1 to 142.255.255.254142.255.255.2554,194,302
61143.0.0.0/10143.0.0.1 to 143.63.255.254143.63.255.2554,194,302
62143.64.0.0/10143.64.0.1 to 143.127.255.254143.127.255.2554,194,302
63143.128.0.0/10143.128.0.1 to 143.191.255.254143.191.255.2554,194,302
64143.192.0.0/10143.192.0.1 to 143.255.255.254143.255.255.2554,194,302
65144.0.0.0/10144.0.0.1 to 144.63.255.254144.63.255.2554,194,302
66144.64.0.0/10144.64.0.1 to 144.127.255.254144.127.255.2554,194,302
67144.128.0.0/10144.128.0.1 to 144.191.255.254144.191.255.2554,194,302
68144.192.0.0/10144.192.0.1 to 144.255.255.254144.255.255.2554,194,302
69145.0.0.0/10145.0.0.1 to 145.63.255.254145.63.255.2554,194,302
70145.64.0.0/10145.64.0.1 to 145.127.255.254145.127.255.2554,194,302
71145.128.0.0/10145.128.0.1 to 145.191.255.254145.191.255.2554,194,302
72145.192.0.0/10145.192.0.1 to 145.255.255.254145.255.255.2554,194,302
73146.0.0.0/10146.0.0.1 to 146.63.255.254146.63.255.2554,194,302
74146.64.0.0/10146.64.0.1 to 146.127.255.254146.127.255.2554,194,302
75146.128.0.0/10146.128.0.1 to 146.191.255.254146.191.255.2554,194,302
76146.192.0.0/10146.192.0.1 to 146.255.255.254146.255.255.2554,194,302
77147.0.0.0/10147.0.0.1 to 147.63.255.254147.63.255.2554,194,302
78147.64.0.0/10147.64.0.1 to 147.127.255.254147.127.255.2554,194,302
79147.128.0.0/10147.128.0.1 to 147.191.255.254147.191.255.2554,194,302
80147.192.0.0/10147.192.0.1 to 147.255.255.254147.255.255.2554,194,302
81148.0.0.0/10148.0.0.1 to 148.63.255.254148.63.255.2554,194,302
82148.64.0.0/10148.64.0.1 to 148.127.255.254148.127.255.2554,194,302
83148.128.0.0/10148.128.0.1 to 148.191.255.254148.191.255.2554,194,302
84148.192.0.0/10148.192.0.1 to 148.255.255.254148.255.255.2554,194,302
85149.0.0.0/10149.0.0.1 to 149.63.255.254149.63.255.2554,194,302
86149.64.0.0/10149.64.0.1 to 149.127.255.254149.127.255.2554,194,302
87149.128.0.0/10149.128.0.1 to 149.191.255.254149.191.255.2554,194,302
88149.192.0.0/10149.192.0.1 to 149.255.255.254149.255.255.2554,194,302
89150.0.0.0/10150.0.0.1 to 150.63.255.254150.63.255.2554,194,302
90150.64.0.0/10150.64.0.1 to 150.127.255.254150.127.255.2554,194,302
91150.128.0.0/10150.128.0.1 to 150.191.255.254150.191.255.2554,194,302
92150.192.0.0/10150.192.0.1 to 150.255.255.254150.255.255.2554,194,302
93151.0.0.0/10151.0.0.1 to 151.63.255.254151.63.255.2554,194,302
94151.64.0.0/10151.64.0.1 to 151.127.255.254151.127.255.2554,194,302
95151.128.0.0/10151.128.0.1 to 151.191.255.254151.191.255.2554,194,302
96151.192.0.0/10151.192.0.1 to 151.255.255.254151.255.255.2554,194,302
97152.0.0.0/10152.0.0.1 to 152.63.255.254152.63.255.2554,194,302
98152.64.0.0/10152.64.0.1 to 152.127.255.254152.127.255.2554,194,302
99152.128.0.0/10152.128.0.1 to 152.191.255.254152.191.255.2554,194,302
100152.192.0.0/10152.192.0.1 to 152.255.255.254152.255.255.2554,194,302
101153.0.0.0/10153.0.0.1 to 153.63.255.254153.63.255.2554,194,302
102153.64.0.0/10153.64.0.1 to 153.127.255.254153.127.255.2554,194,302
103153.128.0.0/10153.128.0.1 to 153.191.255.254153.191.255.2554,194,302
104153.192.0.0/10153.192.0.1 to 153.255.255.254153.255.255.2554,194,302
105154.0.0.0/10154.0.0.1 to 154.63.255.254154.63.255.2554,194,302
106154.64.0.0/10154.64.0.1 to 154.127.255.254154.127.255.2554,194,302
107154.128.0.0/10154.128.0.1 to 154.191.255.254154.191.255.2554,194,302
108154.192.0.0/10154.192.0.1 to 154.255.255.254154.255.255.2554,194,302
109155.0.0.0/10155.0.0.1 to 155.63.255.254155.63.255.2554,194,302
110155.64.0.0/10155.64.0.1 to 155.127.255.254155.127.255.2554,194,302
111155.128.0.0/10155.128.0.1 to 155.191.255.254155.191.255.2554,194,302
112155.192.0.0/10155.192.0.1 to 155.255.255.254155.255.255.2554,194,302
113156.0.0.0/10156.0.0.1 to 156.63.255.254156.63.255.2554,194,302
114156.64.0.0/10156.64.0.1 to 156.127.255.254156.127.255.2554,194,302
115156.128.0.0/10156.128.0.1 to 156.191.255.254156.191.255.2554,194,302
116156.192.0.0/10156.192.0.1 to 156.255.255.254156.255.255.2554,194,302
117157.0.0.0/10157.0.0.1 to 157.63.255.254157.63.255.2554,194,302
118157.64.0.0/10157.64.0.1 to 157.127.255.254157.127.255.2554,194,302
119157.128.0.0/10157.128.0.1 to 157.191.255.254157.191.255.2554,194,302
120157.192.0.0/10157.192.0.1 to 157.255.255.254157.255.255.2554,194,302
121158.0.0.0/10158.0.0.1 to 158.63.255.254158.63.255.2554,194,302
122158.64.0.0/10158.64.0.1 to 158.127.255.254158.127.255.2554,194,302
123158.128.0.0/10158.128.0.1 to 158.191.255.254158.191.255.2554,194,302
124158.192.0.0/10158.192.0.1 to 158.255.255.254158.255.255.2554,194,302
125159.0.0.0/10159.0.0.1 to 159.63.255.254159.63.255.2554,194,302
126159.64.0.0/10159.64.0.1 to 159.127.255.254159.127.255.2554,194,302
127159.128.0.0/10159.128.0.1 to 159.191.255.254159.191.255.2554,194,302
128159.192.0.0/10159.192.0.1 to 159.255.255.254159.255.255.2554,194,302

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.