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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.

Network15.16.0.0/12
Usable hosts1,048,574
Subnet mask255.240.0.0
Addresses1,048,576
Network address
15.16.0.0
Broadcast address
15.31.255.255
First usable
15.16.0.1
Last usable
15.31.255.254
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
Public public
Old class
A (default /8)
As numbers
Hex 0F100000 · Integer 252706816 to 253755391
Reverse DNS zones
16.15.in-addr.arpa
17.15.in-addr.arpa
18.15.in-addr.arpa
19.15.in-addr.arpa
20.15.in-addr.arpa
21.15.in-addr.arpa
22.15.in-addr.arpa
23.15.in-addr.arpa
24.15.in-addr.arpa
25.15.in-addr.arpa
26.15.in-addr.arpa
27.15.in-addr.arpa
28.15.in-addr.arpa
29.15.in-addr.arpa
30.15.in-addr.arpa
31.15.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
Address00001111.00010000.00000000.0000000015.16.0.0
Subnet mask11111111.11110000.00000000.00000000255.240.0.0
Network00001111.00010000.00000000.0000000015.16.0.0
Broadcast00001111.00011111.11111111.1111111115.31.255.255
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)

15.16.0.0/12 makes 128 subnets of /19.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
115.16.0.0/1915.16.0.1 to 15.16.31.25415.16.31.2558,190
215.16.32.0/1915.16.32.1 to 15.16.63.25415.16.63.2558,190
315.16.64.0/1915.16.64.1 to 15.16.95.25415.16.95.2558,190
415.16.96.0/1915.16.96.1 to 15.16.127.25415.16.127.2558,190
515.16.128.0/1915.16.128.1 to 15.16.159.25415.16.159.2558,190
615.16.160.0/1915.16.160.1 to 15.16.191.25415.16.191.2558,190
715.16.192.0/1915.16.192.1 to 15.16.223.25415.16.223.2558,190
815.16.224.0/1915.16.224.1 to 15.16.255.25415.16.255.2558,190
915.17.0.0/1915.17.0.1 to 15.17.31.25415.17.31.2558,190
1015.17.32.0/1915.17.32.1 to 15.17.63.25415.17.63.2558,190
1115.17.64.0/1915.17.64.1 to 15.17.95.25415.17.95.2558,190
1215.17.96.0/1915.17.96.1 to 15.17.127.25415.17.127.2558,190
1315.17.128.0/1915.17.128.1 to 15.17.159.25415.17.159.2558,190
1415.17.160.0/1915.17.160.1 to 15.17.191.25415.17.191.2558,190
1515.17.192.0/1915.17.192.1 to 15.17.223.25415.17.223.2558,190
1615.17.224.0/1915.17.224.1 to 15.17.255.25415.17.255.2558,190
1715.18.0.0/1915.18.0.1 to 15.18.31.25415.18.31.2558,190
1815.18.32.0/1915.18.32.1 to 15.18.63.25415.18.63.2558,190
1915.18.64.0/1915.18.64.1 to 15.18.95.25415.18.95.2558,190
2015.18.96.0/1915.18.96.1 to 15.18.127.25415.18.127.2558,190
2115.18.128.0/1915.18.128.1 to 15.18.159.25415.18.159.2558,190
2215.18.160.0/1915.18.160.1 to 15.18.191.25415.18.191.2558,190
2315.18.192.0/1915.18.192.1 to 15.18.223.25415.18.223.2558,190
2415.18.224.0/1915.18.224.1 to 15.18.255.25415.18.255.2558,190
2515.19.0.0/1915.19.0.1 to 15.19.31.25415.19.31.2558,190
2615.19.32.0/1915.19.32.1 to 15.19.63.25415.19.63.2558,190
2715.19.64.0/1915.19.64.1 to 15.19.95.25415.19.95.2558,190
2815.19.96.0/1915.19.96.1 to 15.19.127.25415.19.127.2558,190
2915.19.128.0/1915.19.128.1 to 15.19.159.25415.19.159.2558,190
3015.19.160.0/1915.19.160.1 to 15.19.191.25415.19.191.2558,190
3115.19.192.0/1915.19.192.1 to 15.19.223.25415.19.223.2558,190
3215.19.224.0/1915.19.224.1 to 15.19.255.25415.19.255.2558,190
3315.20.0.0/1915.20.0.1 to 15.20.31.25415.20.31.2558,190
3415.20.32.0/1915.20.32.1 to 15.20.63.25415.20.63.2558,190
3515.20.64.0/1915.20.64.1 to 15.20.95.25415.20.95.2558,190
3615.20.96.0/1915.20.96.1 to 15.20.127.25415.20.127.2558,190
3715.20.128.0/1915.20.128.1 to 15.20.159.25415.20.159.2558,190
3815.20.160.0/1915.20.160.1 to 15.20.191.25415.20.191.2558,190
3915.20.192.0/1915.20.192.1 to 15.20.223.25415.20.223.2558,190
4015.20.224.0/1915.20.224.1 to 15.20.255.25415.20.255.2558,190
4115.21.0.0/1915.21.0.1 to 15.21.31.25415.21.31.2558,190
4215.21.32.0/1915.21.32.1 to 15.21.63.25415.21.63.2558,190
4315.21.64.0/1915.21.64.1 to 15.21.95.25415.21.95.2558,190
4415.21.96.0/1915.21.96.1 to 15.21.127.25415.21.127.2558,190
4515.21.128.0/1915.21.128.1 to 15.21.159.25415.21.159.2558,190
4615.21.160.0/1915.21.160.1 to 15.21.191.25415.21.191.2558,190
4715.21.192.0/1915.21.192.1 to 15.21.223.25415.21.223.2558,190
4815.21.224.0/1915.21.224.1 to 15.21.255.25415.21.255.2558,190
4915.22.0.0/1915.22.0.1 to 15.22.31.25415.22.31.2558,190
5015.22.32.0/1915.22.32.1 to 15.22.63.25415.22.63.2558,190
5115.22.64.0/1915.22.64.1 to 15.22.95.25415.22.95.2558,190
5215.22.96.0/1915.22.96.1 to 15.22.127.25415.22.127.2558,190
5315.22.128.0/1915.22.128.1 to 15.22.159.25415.22.159.2558,190
5415.22.160.0/1915.22.160.1 to 15.22.191.25415.22.191.2558,190
5515.22.192.0/1915.22.192.1 to 15.22.223.25415.22.223.2558,190
5615.22.224.0/1915.22.224.1 to 15.22.255.25415.22.255.2558,190
5715.23.0.0/1915.23.0.1 to 15.23.31.25415.23.31.2558,190
5815.23.32.0/1915.23.32.1 to 15.23.63.25415.23.63.2558,190
5915.23.64.0/1915.23.64.1 to 15.23.95.25415.23.95.2558,190
6015.23.96.0/1915.23.96.1 to 15.23.127.25415.23.127.2558,190
6115.23.128.0/1915.23.128.1 to 15.23.159.25415.23.159.2558,190
6215.23.160.0/1915.23.160.1 to 15.23.191.25415.23.191.2558,190
6315.23.192.0/1915.23.192.1 to 15.23.223.25415.23.223.2558,190
6415.23.224.0/1915.23.224.1 to 15.23.255.25415.23.255.2558,190
6515.24.0.0/1915.24.0.1 to 15.24.31.25415.24.31.2558,190
6615.24.32.0/1915.24.32.1 to 15.24.63.25415.24.63.2558,190
6715.24.64.0/1915.24.64.1 to 15.24.95.25415.24.95.2558,190
6815.24.96.0/1915.24.96.1 to 15.24.127.25415.24.127.2558,190
6915.24.128.0/1915.24.128.1 to 15.24.159.25415.24.159.2558,190
7015.24.160.0/1915.24.160.1 to 15.24.191.25415.24.191.2558,190
7115.24.192.0/1915.24.192.1 to 15.24.223.25415.24.223.2558,190
7215.24.224.0/1915.24.224.1 to 15.24.255.25415.24.255.2558,190
7315.25.0.0/1915.25.0.1 to 15.25.31.25415.25.31.2558,190
7415.25.32.0/1915.25.32.1 to 15.25.63.25415.25.63.2558,190
7515.25.64.0/1915.25.64.1 to 15.25.95.25415.25.95.2558,190
7615.25.96.0/1915.25.96.1 to 15.25.127.25415.25.127.2558,190
7715.25.128.0/1915.25.128.1 to 15.25.159.25415.25.159.2558,190
7815.25.160.0/1915.25.160.1 to 15.25.191.25415.25.191.2558,190
7915.25.192.0/1915.25.192.1 to 15.25.223.25415.25.223.2558,190
8015.25.224.0/1915.25.224.1 to 15.25.255.25415.25.255.2558,190
8115.26.0.0/1915.26.0.1 to 15.26.31.25415.26.31.2558,190
8215.26.32.0/1915.26.32.1 to 15.26.63.25415.26.63.2558,190
8315.26.64.0/1915.26.64.1 to 15.26.95.25415.26.95.2558,190
8415.26.96.0/1915.26.96.1 to 15.26.127.25415.26.127.2558,190
8515.26.128.0/1915.26.128.1 to 15.26.159.25415.26.159.2558,190
8615.26.160.0/1915.26.160.1 to 15.26.191.25415.26.191.2558,190
8715.26.192.0/1915.26.192.1 to 15.26.223.25415.26.223.2558,190
8815.26.224.0/1915.26.224.1 to 15.26.255.25415.26.255.2558,190
8915.27.0.0/1915.27.0.1 to 15.27.31.25415.27.31.2558,190
9015.27.32.0/1915.27.32.1 to 15.27.63.25415.27.63.2558,190
9115.27.64.0/1915.27.64.1 to 15.27.95.25415.27.95.2558,190
9215.27.96.0/1915.27.96.1 to 15.27.127.25415.27.127.2558,190
9315.27.128.0/1915.27.128.1 to 15.27.159.25415.27.159.2558,190
9415.27.160.0/1915.27.160.1 to 15.27.191.25415.27.191.2558,190
9515.27.192.0/1915.27.192.1 to 15.27.223.25415.27.223.2558,190
9615.27.224.0/1915.27.224.1 to 15.27.255.25415.27.255.2558,190
9715.28.0.0/1915.28.0.1 to 15.28.31.25415.28.31.2558,190
9815.28.32.0/1915.28.32.1 to 15.28.63.25415.28.63.2558,190
9915.28.64.0/1915.28.64.1 to 15.28.95.25415.28.95.2558,190
10015.28.96.0/1915.28.96.1 to 15.28.127.25415.28.127.2558,190
10115.28.128.0/1915.28.128.1 to 15.28.159.25415.28.159.2558,190
10215.28.160.0/1915.28.160.1 to 15.28.191.25415.28.191.2558,190
10315.28.192.0/1915.28.192.1 to 15.28.223.25415.28.223.2558,190
10415.28.224.0/1915.28.224.1 to 15.28.255.25415.28.255.2558,190
10515.29.0.0/1915.29.0.1 to 15.29.31.25415.29.31.2558,190
10615.29.32.0/1915.29.32.1 to 15.29.63.25415.29.63.2558,190
10715.29.64.0/1915.29.64.1 to 15.29.95.25415.29.95.2558,190
10815.29.96.0/1915.29.96.1 to 15.29.127.25415.29.127.2558,190
10915.29.128.0/1915.29.128.1 to 15.29.159.25415.29.159.2558,190
11015.29.160.0/1915.29.160.1 to 15.29.191.25415.29.191.2558,190
11115.29.192.0/1915.29.192.1 to 15.29.223.25415.29.223.2558,190
11215.29.224.0/1915.29.224.1 to 15.29.255.25415.29.255.2558,190
11315.30.0.0/1915.30.0.1 to 15.30.31.25415.30.31.2558,190
11415.30.32.0/1915.30.32.1 to 15.30.63.25415.30.63.2558,190
11515.30.64.0/1915.30.64.1 to 15.30.95.25415.30.95.2558,190
11615.30.96.0/1915.30.96.1 to 15.30.127.25415.30.127.2558,190
11715.30.128.0/1915.30.128.1 to 15.30.159.25415.30.159.2558,190
11815.30.160.0/1915.30.160.1 to 15.30.191.25415.30.191.2558,190
11915.30.192.0/1915.30.192.1 to 15.30.223.25415.30.223.2558,190
12015.30.224.0/1915.30.224.1 to 15.30.255.25415.30.255.2558,190
12115.31.0.0/1915.31.0.1 to 15.31.31.25415.31.31.2558,190
12215.31.32.0/1915.31.32.1 to 15.31.63.25415.31.63.2558,190
12315.31.64.0/1915.31.64.1 to 15.31.95.25415.31.95.2558,190
12415.31.96.0/1915.31.96.1 to 15.31.127.25415.31.127.2558,190
12515.31.128.0/1915.31.128.1 to 15.31.159.25415.31.159.2558,190
12615.31.160.0/1915.31.160.1 to 15.31.191.25415.31.191.2558,190
12715.31.192.0/1915.31.192.1 to 15.31.223.25415.31.223.2558,190
12815.31.224.0/1915.31.224.1 to 15.31.255.25415.31.255.2558,190

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.