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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.

Network151.4.0.0/17
Usable hosts32,766
Subnet mask255.255.128.0
Addresses32,768
Network address
151.4.0.0
Broadcast address
151.4.127.255
First usable
151.4.0.1
Last usable
151.4.127.254
Usable hosts
32,766 (32,768 less the network and broadcast addresses)
Subnet mask
255.255.128.0
Wildcard mask
0.0.127.255 (Cisco ACLs, OSPF)
Prefix length
/17
Type
Public public
Old class
B (default /16)
As numbers
Hex 97040000 · Integer 2533621760 to 2533654527
Reverse DNS zones
0.4.151.in-addr.arpa
1.4.151.in-addr.arpa
2.4.151.in-addr.arpa
3.4.151.in-addr.arpa
4.4.151.in-addr.arpa
5.4.151.in-addr.arpa
6.4.151.in-addr.arpa
7.4.151.in-addr.arpa
8.4.151.in-addr.arpa
9.4.151.in-addr.arpa
10.4.151.in-addr.arpa
11.4.151.in-addr.arpa
12.4.151.in-addr.arpa
13.4.151.in-addr.arpa
14.4.151.in-addr.arpa
15.4.151.in-addr.arpa
and 112 more
/17 is not on a 8-bit boundary, so it takes 128 /24 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10010111.00000100.00000000.00000000151.4.0.0
Subnet mask11111111.11111111.10000000.00000000255.255.128.0
Network10010111.00000100.00000000.00000000151.4.0.0
Broadcast10010111.00000100.01111111.11111111151.4.127.255
Split into smaller subnets/24
/18 (2)/19 (4)/20 (8)/21 (16)/22 (32)/23 (64)/24 (128)/25 (256)/26 (512)/27 (1,024)/28 (2,048)/29 (4,096)

151.4.0.0/17 makes 128 subnets of /24.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1151.4.0.0/24151.4.0.1 to 151.4.0.254151.4.0.255254
2151.4.1.0/24151.4.1.1 to 151.4.1.254151.4.1.255254
3151.4.2.0/24151.4.2.1 to 151.4.2.254151.4.2.255254
4151.4.3.0/24151.4.3.1 to 151.4.3.254151.4.3.255254
5151.4.4.0/24151.4.4.1 to 151.4.4.254151.4.4.255254
6151.4.5.0/24151.4.5.1 to 151.4.5.254151.4.5.255254
7151.4.6.0/24151.4.6.1 to 151.4.6.254151.4.6.255254
8151.4.7.0/24151.4.7.1 to 151.4.7.254151.4.7.255254
9151.4.8.0/24151.4.8.1 to 151.4.8.254151.4.8.255254
10151.4.9.0/24151.4.9.1 to 151.4.9.254151.4.9.255254
11151.4.10.0/24151.4.10.1 to 151.4.10.254151.4.10.255254
12151.4.11.0/24151.4.11.1 to 151.4.11.254151.4.11.255254
13151.4.12.0/24151.4.12.1 to 151.4.12.254151.4.12.255254
14151.4.13.0/24151.4.13.1 to 151.4.13.254151.4.13.255254
15151.4.14.0/24151.4.14.1 to 151.4.14.254151.4.14.255254
16151.4.15.0/24151.4.15.1 to 151.4.15.254151.4.15.255254
17151.4.16.0/24151.4.16.1 to 151.4.16.254151.4.16.255254
18151.4.17.0/24151.4.17.1 to 151.4.17.254151.4.17.255254
19151.4.18.0/24151.4.18.1 to 151.4.18.254151.4.18.255254
20151.4.19.0/24151.4.19.1 to 151.4.19.254151.4.19.255254
21151.4.20.0/24151.4.20.1 to 151.4.20.254151.4.20.255254
22151.4.21.0/24151.4.21.1 to 151.4.21.254151.4.21.255254
23151.4.22.0/24151.4.22.1 to 151.4.22.254151.4.22.255254
24151.4.23.0/24151.4.23.1 to 151.4.23.254151.4.23.255254
25151.4.24.0/24151.4.24.1 to 151.4.24.254151.4.24.255254
26151.4.25.0/24151.4.25.1 to 151.4.25.254151.4.25.255254
27151.4.26.0/24151.4.26.1 to 151.4.26.254151.4.26.255254
28151.4.27.0/24151.4.27.1 to 151.4.27.254151.4.27.255254
29151.4.28.0/24151.4.28.1 to 151.4.28.254151.4.28.255254
30151.4.29.0/24151.4.29.1 to 151.4.29.254151.4.29.255254
31151.4.30.0/24151.4.30.1 to 151.4.30.254151.4.30.255254
32151.4.31.0/24151.4.31.1 to 151.4.31.254151.4.31.255254
33151.4.32.0/24151.4.32.1 to 151.4.32.254151.4.32.255254
34151.4.33.0/24151.4.33.1 to 151.4.33.254151.4.33.255254
35151.4.34.0/24151.4.34.1 to 151.4.34.254151.4.34.255254
36151.4.35.0/24151.4.35.1 to 151.4.35.254151.4.35.255254
37151.4.36.0/24151.4.36.1 to 151.4.36.254151.4.36.255254
38151.4.37.0/24151.4.37.1 to 151.4.37.254151.4.37.255254
39151.4.38.0/24151.4.38.1 to 151.4.38.254151.4.38.255254
40151.4.39.0/24151.4.39.1 to 151.4.39.254151.4.39.255254
41151.4.40.0/24151.4.40.1 to 151.4.40.254151.4.40.255254
42151.4.41.0/24151.4.41.1 to 151.4.41.254151.4.41.255254
43151.4.42.0/24151.4.42.1 to 151.4.42.254151.4.42.255254
44151.4.43.0/24151.4.43.1 to 151.4.43.254151.4.43.255254
45151.4.44.0/24151.4.44.1 to 151.4.44.254151.4.44.255254
46151.4.45.0/24151.4.45.1 to 151.4.45.254151.4.45.255254
47151.4.46.0/24151.4.46.1 to 151.4.46.254151.4.46.255254
48151.4.47.0/24151.4.47.1 to 151.4.47.254151.4.47.255254
49151.4.48.0/24151.4.48.1 to 151.4.48.254151.4.48.255254
50151.4.49.0/24151.4.49.1 to 151.4.49.254151.4.49.255254
51151.4.50.0/24151.4.50.1 to 151.4.50.254151.4.50.255254
52151.4.51.0/24151.4.51.1 to 151.4.51.254151.4.51.255254
53151.4.52.0/24151.4.52.1 to 151.4.52.254151.4.52.255254
54151.4.53.0/24151.4.53.1 to 151.4.53.254151.4.53.255254
55151.4.54.0/24151.4.54.1 to 151.4.54.254151.4.54.255254
56151.4.55.0/24151.4.55.1 to 151.4.55.254151.4.55.255254
57151.4.56.0/24151.4.56.1 to 151.4.56.254151.4.56.255254
58151.4.57.0/24151.4.57.1 to 151.4.57.254151.4.57.255254
59151.4.58.0/24151.4.58.1 to 151.4.58.254151.4.58.255254
60151.4.59.0/24151.4.59.1 to 151.4.59.254151.4.59.255254
61151.4.60.0/24151.4.60.1 to 151.4.60.254151.4.60.255254
62151.4.61.0/24151.4.61.1 to 151.4.61.254151.4.61.255254
63151.4.62.0/24151.4.62.1 to 151.4.62.254151.4.62.255254
64151.4.63.0/24151.4.63.1 to 151.4.63.254151.4.63.255254
65151.4.64.0/24151.4.64.1 to 151.4.64.254151.4.64.255254
66151.4.65.0/24151.4.65.1 to 151.4.65.254151.4.65.255254
67151.4.66.0/24151.4.66.1 to 151.4.66.254151.4.66.255254
68151.4.67.0/24151.4.67.1 to 151.4.67.254151.4.67.255254
69151.4.68.0/24151.4.68.1 to 151.4.68.254151.4.68.255254
70151.4.69.0/24151.4.69.1 to 151.4.69.254151.4.69.255254
71151.4.70.0/24151.4.70.1 to 151.4.70.254151.4.70.255254
72151.4.71.0/24151.4.71.1 to 151.4.71.254151.4.71.255254
73151.4.72.0/24151.4.72.1 to 151.4.72.254151.4.72.255254
74151.4.73.0/24151.4.73.1 to 151.4.73.254151.4.73.255254
75151.4.74.0/24151.4.74.1 to 151.4.74.254151.4.74.255254
76151.4.75.0/24151.4.75.1 to 151.4.75.254151.4.75.255254
77151.4.76.0/24151.4.76.1 to 151.4.76.254151.4.76.255254
78151.4.77.0/24151.4.77.1 to 151.4.77.254151.4.77.255254
79151.4.78.0/24151.4.78.1 to 151.4.78.254151.4.78.255254
80151.4.79.0/24151.4.79.1 to 151.4.79.254151.4.79.255254
81151.4.80.0/24151.4.80.1 to 151.4.80.254151.4.80.255254
82151.4.81.0/24151.4.81.1 to 151.4.81.254151.4.81.255254
83151.4.82.0/24151.4.82.1 to 151.4.82.254151.4.82.255254
84151.4.83.0/24151.4.83.1 to 151.4.83.254151.4.83.255254
85151.4.84.0/24151.4.84.1 to 151.4.84.254151.4.84.255254
86151.4.85.0/24151.4.85.1 to 151.4.85.254151.4.85.255254
87151.4.86.0/24151.4.86.1 to 151.4.86.254151.4.86.255254
88151.4.87.0/24151.4.87.1 to 151.4.87.254151.4.87.255254
89151.4.88.0/24151.4.88.1 to 151.4.88.254151.4.88.255254
90151.4.89.0/24151.4.89.1 to 151.4.89.254151.4.89.255254
91151.4.90.0/24151.4.90.1 to 151.4.90.254151.4.90.255254
92151.4.91.0/24151.4.91.1 to 151.4.91.254151.4.91.255254
93151.4.92.0/24151.4.92.1 to 151.4.92.254151.4.92.255254
94151.4.93.0/24151.4.93.1 to 151.4.93.254151.4.93.255254
95151.4.94.0/24151.4.94.1 to 151.4.94.254151.4.94.255254
96151.4.95.0/24151.4.95.1 to 151.4.95.254151.4.95.255254
97151.4.96.0/24151.4.96.1 to 151.4.96.254151.4.96.255254
98151.4.97.0/24151.4.97.1 to 151.4.97.254151.4.97.255254
99151.4.98.0/24151.4.98.1 to 151.4.98.254151.4.98.255254
100151.4.99.0/24151.4.99.1 to 151.4.99.254151.4.99.255254
101151.4.100.0/24151.4.100.1 to 151.4.100.254151.4.100.255254
102151.4.101.0/24151.4.101.1 to 151.4.101.254151.4.101.255254
103151.4.102.0/24151.4.102.1 to 151.4.102.254151.4.102.255254
104151.4.103.0/24151.4.103.1 to 151.4.103.254151.4.103.255254
105151.4.104.0/24151.4.104.1 to 151.4.104.254151.4.104.255254
106151.4.105.0/24151.4.105.1 to 151.4.105.254151.4.105.255254
107151.4.106.0/24151.4.106.1 to 151.4.106.254151.4.106.255254
108151.4.107.0/24151.4.107.1 to 151.4.107.254151.4.107.255254
109151.4.108.0/24151.4.108.1 to 151.4.108.254151.4.108.255254
110151.4.109.0/24151.4.109.1 to 151.4.109.254151.4.109.255254
111151.4.110.0/24151.4.110.1 to 151.4.110.254151.4.110.255254
112151.4.111.0/24151.4.111.1 to 151.4.111.254151.4.111.255254
113151.4.112.0/24151.4.112.1 to 151.4.112.254151.4.112.255254
114151.4.113.0/24151.4.113.1 to 151.4.113.254151.4.113.255254
115151.4.114.0/24151.4.114.1 to 151.4.114.254151.4.114.255254
116151.4.115.0/24151.4.115.1 to 151.4.115.254151.4.115.255254
117151.4.116.0/24151.4.116.1 to 151.4.116.254151.4.116.255254
118151.4.117.0/24151.4.117.1 to 151.4.117.254151.4.117.255254
119151.4.118.0/24151.4.118.1 to 151.4.118.254151.4.118.255254
120151.4.119.0/24151.4.119.1 to 151.4.119.254151.4.119.255254
121151.4.120.0/24151.4.120.1 to 151.4.120.254151.4.120.255254
122151.4.121.0/24151.4.121.1 to 151.4.121.254151.4.121.255254
123151.4.122.0/24151.4.122.1 to 151.4.122.254151.4.122.255254
124151.4.123.0/24151.4.123.1 to 151.4.123.254151.4.123.255254
125151.4.124.0/24151.4.124.1 to 151.4.124.254151.4.124.255254
126151.4.125.0/24151.4.125.1 to 151.4.125.254151.4.125.255254
127151.4.126.0/24151.4.126.1 to 151.4.126.254151.4.126.255254
128151.4.127.0/24151.4.127.1 to 151.4.127.254151.4.127.255254

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.