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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.

Network157.76.0.0/15
Usable hosts131,070
Subnet mask255.254.0.0
Addresses131,072
Network address
157.76.0.0
Broadcast address
157.77.255.255
First usable
157.76.0.1
Last usable
157.77.255.254
Usable hosts
131,070 (131,072 less the network and broadcast addresses)
Subnet mask
255.254.0.0
Wildcard mask
0.1.255.255 (Cisco ACLs, OSPF)
Prefix length
/15
Type
Public public
Old class
B (default /16)
As numbers
Hex 9D4C0000 · Integer 2639003648 to 2639134719
Reverse DNS zones
76.157.in-addr.arpa
77.157.in-addr.arpa
/15 is not on a 8-bit boundary, so it takes 2 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address10011101.01001100.00000000.00000000157.76.0.0
Subnet mask11111111.11111110.00000000.00000000255.254.0.0
Network10011101.01001100.00000000.00000000157.76.0.0
Broadcast10011101.01001101.11111111.11111111157.77.255.255
Split into smaller subnets/21
/16 (2)/17 (4)/18 (8)/19 (16)/20 (32)/21 (64)/22 (128)/23 (256)/24 (512)/25 (1,024)/26 (2,048)/27 (4,096)

157.76.0.0/15 makes 64 subnets of /21.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
1157.76.0.0/21157.76.0.1 to 157.76.7.254157.76.7.2552,046
2157.76.8.0/21157.76.8.1 to 157.76.15.254157.76.15.2552,046
3157.76.16.0/21157.76.16.1 to 157.76.23.254157.76.23.2552,046
4157.76.24.0/21157.76.24.1 to 157.76.31.254157.76.31.2552,046
5157.76.32.0/21157.76.32.1 to 157.76.39.254157.76.39.2552,046
6157.76.40.0/21157.76.40.1 to 157.76.47.254157.76.47.2552,046
7157.76.48.0/21157.76.48.1 to 157.76.55.254157.76.55.2552,046
8157.76.56.0/21157.76.56.1 to 157.76.63.254157.76.63.2552,046
9157.76.64.0/21157.76.64.1 to 157.76.71.254157.76.71.2552,046
10157.76.72.0/21157.76.72.1 to 157.76.79.254157.76.79.2552,046
11157.76.80.0/21157.76.80.1 to 157.76.87.254157.76.87.2552,046
12157.76.88.0/21157.76.88.1 to 157.76.95.254157.76.95.2552,046
13157.76.96.0/21157.76.96.1 to 157.76.103.254157.76.103.2552,046
14157.76.104.0/21157.76.104.1 to 157.76.111.254157.76.111.2552,046
15157.76.112.0/21157.76.112.1 to 157.76.119.254157.76.119.2552,046
16157.76.120.0/21157.76.120.1 to 157.76.127.254157.76.127.2552,046
17157.76.128.0/21157.76.128.1 to 157.76.135.254157.76.135.2552,046
18157.76.136.0/21157.76.136.1 to 157.76.143.254157.76.143.2552,046
19157.76.144.0/21157.76.144.1 to 157.76.151.254157.76.151.2552,046
20157.76.152.0/21157.76.152.1 to 157.76.159.254157.76.159.2552,046
21157.76.160.0/21157.76.160.1 to 157.76.167.254157.76.167.2552,046
22157.76.168.0/21157.76.168.1 to 157.76.175.254157.76.175.2552,046
23157.76.176.0/21157.76.176.1 to 157.76.183.254157.76.183.2552,046
24157.76.184.0/21157.76.184.1 to 157.76.191.254157.76.191.2552,046
25157.76.192.0/21157.76.192.1 to 157.76.199.254157.76.199.2552,046
26157.76.200.0/21157.76.200.1 to 157.76.207.254157.76.207.2552,046
27157.76.208.0/21157.76.208.1 to 157.76.215.254157.76.215.2552,046
28157.76.216.0/21157.76.216.1 to 157.76.223.254157.76.223.2552,046
29157.76.224.0/21157.76.224.1 to 157.76.231.254157.76.231.2552,046
30157.76.232.0/21157.76.232.1 to 157.76.239.254157.76.239.2552,046
31157.76.240.0/21157.76.240.1 to 157.76.247.254157.76.247.2552,046
32157.76.248.0/21157.76.248.1 to 157.76.255.254157.76.255.2552,046
33157.77.0.0/21157.77.0.1 to 157.77.7.254157.77.7.2552,046
34157.77.8.0/21157.77.8.1 to 157.77.15.254157.77.15.2552,046
35157.77.16.0/21157.77.16.1 to 157.77.23.254157.77.23.2552,046
36157.77.24.0/21157.77.24.1 to 157.77.31.254157.77.31.2552,046
37157.77.32.0/21157.77.32.1 to 157.77.39.254157.77.39.2552,046
38157.77.40.0/21157.77.40.1 to 157.77.47.254157.77.47.2552,046
39157.77.48.0/21157.77.48.1 to 157.77.55.254157.77.55.2552,046
40157.77.56.0/21157.77.56.1 to 157.77.63.254157.77.63.2552,046
41157.77.64.0/21157.77.64.1 to 157.77.71.254157.77.71.2552,046
42157.77.72.0/21157.77.72.1 to 157.77.79.254157.77.79.2552,046
43157.77.80.0/21157.77.80.1 to 157.77.87.254157.77.87.2552,046
44157.77.88.0/21157.77.88.1 to 157.77.95.254157.77.95.2552,046
45157.77.96.0/21157.77.96.1 to 157.77.103.254157.77.103.2552,046
46157.77.104.0/21157.77.104.1 to 157.77.111.254157.77.111.2552,046
47157.77.112.0/21157.77.112.1 to 157.77.119.254157.77.119.2552,046
48157.77.120.0/21157.77.120.1 to 157.77.127.254157.77.127.2552,046
49157.77.128.0/21157.77.128.1 to 157.77.135.254157.77.135.2552,046
50157.77.136.0/21157.77.136.1 to 157.77.143.254157.77.143.2552,046
51157.77.144.0/21157.77.144.1 to 157.77.151.254157.77.151.2552,046
52157.77.152.0/21157.77.152.1 to 157.77.159.254157.77.159.2552,046
53157.77.160.0/21157.77.160.1 to 157.77.167.254157.77.167.2552,046
54157.77.168.0/21157.77.168.1 to 157.77.175.254157.77.175.2552,046
55157.77.176.0/21157.77.176.1 to 157.77.183.254157.77.183.2552,046
56157.77.184.0/21157.77.184.1 to 157.77.191.254157.77.191.2552,046
57157.77.192.0/21157.77.192.1 to 157.77.199.254157.77.199.2552,046
58157.77.200.0/21157.77.200.1 to 157.77.207.254157.77.207.2552,046
59157.77.208.0/21157.77.208.1 to 157.77.215.254157.77.215.2552,046
60157.77.216.0/21157.77.216.1 to 157.77.223.254157.77.223.2552,046
61157.77.224.0/21157.77.224.1 to 157.77.231.254157.77.231.2552,046
62157.77.232.0/21157.77.232.1 to 157.77.239.254157.77.239.2552,046
63157.77.240.0/21157.77.240.1 to 157.77.247.254157.77.247.2552,046
64157.77.248.0/21157.77.248.1 to 157.77.255.254157.77.255.2552,046

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.