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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.

Network241.32.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
241.32.0.0
Broadcast address
241.47.255.255
First usable
241.32.0.1
Last usable
241.47.255.254
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 F1200000 · Integer 4045406208 to 4046454783
Reverse DNS zones
32.241.in-addr.arpa
33.241.in-addr.arpa
34.241.in-addr.arpa
35.241.in-addr.arpa
36.241.in-addr.arpa
37.241.in-addr.arpa
38.241.in-addr.arpa
39.241.in-addr.arpa
40.241.in-addr.arpa
41.241.in-addr.arpa
42.241.in-addr.arpa
43.241.in-addr.arpa
44.241.in-addr.arpa
45.241.in-addr.arpa
46.241.in-addr.arpa
47.241.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
Address11110001.00100000.00000000.00000000241.32.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network11110001.00100000.00000000.00000000241.32.0.0
Broadcast11110001.00101111.11111111.11111111241.47.255.255
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)

241.32.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1241.32.0.0/19241.32.0.1 to 241.32.31.254241.32.31.2558,190
2241.32.32.0/19241.32.32.1 to 241.32.63.254241.32.63.2558,190
3241.32.64.0/19241.32.64.1 to 241.32.95.254241.32.95.2558,190
4241.32.96.0/19241.32.96.1 to 241.32.127.254241.32.127.2558,190
5241.32.128.0/19241.32.128.1 to 241.32.159.254241.32.159.2558,190
6241.32.160.0/19241.32.160.1 to 241.32.191.254241.32.191.2558,190
7241.32.192.0/19241.32.192.1 to 241.32.223.254241.32.223.2558,190
8241.32.224.0/19241.32.224.1 to 241.32.255.254241.32.255.2558,190
9241.33.0.0/19241.33.0.1 to 241.33.31.254241.33.31.2558,190
10241.33.32.0/19241.33.32.1 to 241.33.63.254241.33.63.2558,190
11241.33.64.0/19241.33.64.1 to 241.33.95.254241.33.95.2558,190
12241.33.96.0/19241.33.96.1 to 241.33.127.254241.33.127.2558,190
13241.33.128.0/19241.33.128.1 to 241.33.159.254241.33.159.2558,190
14241.33.160.0/19241.33.160.1 to 241.33.191.254241.33.191.2558,190
15241.33.192.0/19241.33.192.1 to 241.33.223.254241.33.223.2558,190
16241.33.224.0/19241.33.224.1 to 241.33.255.254241.33.255.2558,190
17241.34.0.0/19241.34.0.1 to 241.34.31.254241.34.31.2558,190
18241.34.32.0/19241.34.32.1 to 241.34.63.254241.34.63.2558,190
19241.34.64.0/19241.34.64.1 to 241.34.95.254241.34.95.2558,190
20241.34.96.0/19241.34.96.1 to 241.34.127.254241.34.127.2558,190
21241.34.128.0/19241.34.128.1 to 241.34.159.254241.34.159.2558,190
22241.34.160.0/19241.34.160.1 to 241.34.191.254241.34.191.2558,190
23241.34.192.0/19241.34.192.1 to 241.34.223.254241.34.223.2558,190
24241.34.224.0/19241.34.224.1 to 241.34.255.254241.34.255.2558,190
25241.35.0.0/19241.35.0.1 to 241.35.31.254241.35.31.2558,190
26241.35.32.0/19241.35.32.1 to 241.35.63.254241.35.63.2558,190
27241.35.64.0/19241.35.64.1 to 241.35.95.254241.35.95.2558,190
28241.35.96.0/19241.35.96.1 to 241.35.127.254241.35.127.2558,190
29241.35.128.0/19241.35.128.1 to 241.35.159.254241.35.159.2558,190
30241.35.160.0/19241.35.160.1 to 241.35.191.254241.35.191.2558,190
31241.35.192.0/19241.35.192.1 to 241.35.223.254241.35.223.2558,190
32241.35.224.0/19241.35.224.1 to 241.35.255.254241.35.255.2558,190
33241.36.0.0/19241.36.0.1 to 241.36.31.254241.36.31.2558,190
34241.36.32.0/19241.36.32.1 to 241.36.63.254241.36.63.2558,190
35241.36.64.0/19241.36.64.1 to 241.36.95.254241.36.95.2558,190
36241.36.96.0/19241.36.96.1 to 241.36.127.254241.36.127.2558,190
37241.36.128.0/19241.36.128.1 to 241.36.159.254241.36.159.2558,190
38241.36.160.0/19241.36.160.1 to 241.36.191.254241.36.191.2558,190
39241.36.192.0/19241.36.192.1 to 241.36.223.254241.36.223.2558,190
40241.36.224.0/19241.36.224.1 to 241.36.255.254241.36.255.2558,190
41241.37.0.0/19241.37.0.1 to 241.37.31.254241.37.31.2558,190
42241.37.32.0/19241.37.32.1 to 241.37.63.254241.37.63.2558,190
43241.37.64.0/19241.37.64.1 to 241.37.95.254241.37.95.2558,190
44241.37.96.0/19241.37.96.1 to 241.37.127.254241.37.127.2558,190
45241.37.128.0/19241.37.128.1 to 241.37.159.254241.37.159.2558,190
46241.37.160.0/19241.37.160.1 to 241.37.191.254241.37.191.2558,190
47241.37.192.0/19241.37.192.1 to 241.37.223.254241.37.223.2558,190
48241.37.224.0/19241.37.224.1 to 241.37.255.254241.37.255.2558,190
49241.38.0.0/19241.38.0.1 to 241.38.31.254241.38.31.2558,190
50241.38.32.0/19241.38.32.1 to 241.38.63.254241.38.63.2558,190
51241.38.64.0/19241.38.64.1 to 241.38.95.254241.38.95.2558,190
52241.38.96.0/19241.38.96.1 to 241.38.127.254241.38.127.2558,190
53241.38.128.0/19241.38.128.1 to 241.38.159.254241.38.159.2558,190
54241.38.160.0/19241.38.160.1 to 241.38.191.254241.38.191.2558,190
55241.38.192.0/19241.38.192.1 to 241.38.223.254241.38.223.2558,190
56241.38.224.0/19241.38.224.1 to 241.38.255.254241.38.255.2558,190
57241.39.0.0/19241.39.0.1 to 241.39.31.254241.39.31.2558,190
58241.39.32.0/19241.39.32.1 to 241.39.63.254241.39.63.2558,190
59241.39.64.0/19241.39.64.1 to 241.39.95.254241.39.95.2558,190
60241.39.96.0/19241.39.96.1 to 241.39.127.254241.39.127.2558,190
61241.39.128.0/19241.39.128.1 to 241.39.159.254241.39.159.2558,190
62241.39.160.0/19241.39.160.1 to 241.39.191.254241.39.191.2558,190
63241.39.192.0/19241.39.192.1 to 241.39.223.254241.39.223.2558,190
64241.39.224.0/19241.39.224.1 to 241.39.255.254241.39.255.2558,190
65241.40.0.0/19241.40.0.1 to 241.40.31.254241.40.31.2558,190
66241.40.32.0/19241.40.32.1 to 241.40.63.254241.40.63.2558,190
67241.40.64.0/19241.40.64.1 to 241.40.95.254241.40.95.2558,190
68241.40.96.0/19241.40.96.1 to 241.40.127.254241.40.127.2558,190
69241.40.128.0/19241.40.128.1 to 241.40.159.254241.40.159.2558,190
70241.40.160.0/19241.40.160.1 to 241.40.191.254241.40.191.2558,190
71241.40.192.0/19241.40.192.1 to 241.40.223.254241.40.223.2558,190
72241.40.224.0/19241.40.224.1 to 241.40.255.254241.40.255.2558,190
73241.41.0.0/19241.41.0.1 to 241.41.31.254241.41.31.2558,190
74241.41.32.0/19241.41.32.1 to 241.41.63.254241.41.63.2558,190
75241.41.64.0/19241.41.64.1 to 241.41.95.254241.41.95.2558,190
76241.41.96.0/19241.41.96.1 to 241.41.127.254241.41.127.2558,190
77241.41.128.0/19241.41.128.1 to 241.41.159.254241.41.159.2558,190
78241.41.160.0/19241.41.160.1 to 241.41.191.254241.41.191.2558,190
79241.41.192.0/19241.41.192.1 to 241.41.223.254241.41.223.2558,190
80241.41.224.0/19241.41.224.1 to 241.41.255.254241.41.255.2558,190
81241.42.0.0/19241.42.0.1 to 241.42.31.254241.42.31.2558,190
82241.42.32.0/19241.42.32.1 to 241.42.63.254241.42.63.2558,190
83241.42.64.0/19241.42.64.1 to 241.42.95.254241.42.95.2558,190
84241.42.96.0/19241.42.96.1 to 241.42.127.254241.42.127.2558,190
85241.42.128.0/19241.42.128.1 to 241.42.159.254241.42.159.2558,190
86241.42.160.0/19241.42.160.1 to 241.42.191.254241.42.191.2558,190
87241.42.192.0/19241.42.192.1 to 241.42.223.254241.42.223.2558,190
88241.42.224.0/19241.42.224.1 to 241.42.255.254241.42.255.2558,190
89241.43.0.0/19241.43.0.1 to 241.43.31.254241.43.31.2558,190
90241.43.32.0/19241.43.32.1 to 241.43.63.254241.43.63.2558,190
91241.43.64.0/19241.43.64.1 to 241.43.95.254241.43.95.2558,190
92241.43.96.0/19241.43.96.1 to 241.43.127.254241.43.127.2558,190
93241.43.128.0/19241.43.128.1 to 241.43.159.254241.43.159.2558,190
94241.43.160.0/19241.43.160.1 to 241.43.191.254241.43.191.2558,190
95241.43.192.0/19241.43.192.1 to 241.43.223.254241.43.223.2558,190
96241.43.224.0/19241.43.224.1 to 241.43.255.254241.43.255.2558,190
97241.44.0.0/19241.44.0.1 to 241.44.31.254241.44.31.2558,190
98241.44.32.0/19241.44.32.1 to 241.44.63.254241.44.63.2558,190
99241.44.64.0/19241.44.64.1 to 241.44.95.254241.44.95.2558,190
100241.44.96.0/19241.44.96.1 to 241.44.127.254241.44.127.2558,190
101241.44.128.0/19241.44.128.1 to 241.44.159.254241.44.159.2558,190
102241.44.160.0/19241.44.160.1 to 241.44.191.254241.44.191.2558,190
103241.44.192.0/19241.44.192.1 to 241.44.223.254241.44.223.2558,190
104241.44.224.0/19241.44.224.1 to 241.44.255.254241.44.255.2558,190
105241.45.0.0/19241.45.0.1 to 241.45.31.254241.45.31.2558,190
106241.45.32.0/19241.45.32.1 to 241.45.63.254241.45.63.2558,190
107241.45.64.0/19241.45.64.1 to 241.45.95.254241.45.95.2558,190
108241.45.96.0/19241.45.96.1 to 241.45.127.254241.45.127.2558,190
109241.45.128.0/19241.45.128.1 to 241.45.159.254241.45.159.2558,190
110241.45.160.0/19241.45.160.1 to 241.45.191.254241.45.191.2558,190
111241.45.192.0/19241.45.192.1 to 241.45.223.254241.45.223.2558,190
112241.45.224.0/19241.45.224.1 to 241.45.255.254241.45.255.2558,190
113241.46.0.0/19241.46.0.1 to 241.46.31.254241.46.31.2558,190
114241.46.32.0/19241.46.32.1 to 241.46.63.254241.46.63.2558,190
115241.46.64.0/19241.46.64.1 to 241.46.95.254241.46.95.2558,190
116241.46.96.0/19241.46.96.1 to 241.46.127.254241.46.127.2558,190
117241.46.128.0/19241.46.128.1 to 241.46.159.254241.46.159.2558,190
118241.46.160.0/19241.46.160.1 to 241.46.191.254241.46.191.2558,190
119241.46.192.0/19241.46.192.1 to 241.46.223.254241.46.223.2558,190
120241.46.224.0/19241.46.224.1 to 241.46.255.254241.46.255.2558,190
121241.47.0.0/19241.47.0.1 to 241.47.31.254241.47.31.2558,190
122241.47.32.0/19241.47.32.1 to 241.47.63.254241.47.63.2558,190
123241.47.64.0/19241.47.64.1 to 241.47.95.254241.47.95.2558,190
124241.47.96.0/19241.47.96.1 to 241.47.127.254241.47.127.2558,190
125241.47.128.0/19241.47.128.1 to 241.47.159.254241.47.159.2558,190
126241.47.160.0/19241.47.160.1 to 241.47.191.254241.47.191.2558,190
127241.47.192.0/19241.47.192.1 to 241.47.223.254241.47.223.2558,190
128241.47.224.0/19241.47.224.1 to 241.47.255.254241.47.255.2558,190

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.