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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.

Network28.0.0.0/10
Usable hosts4,194,302
Subnet mask255.192.0.0
Addresses4,194,304
Network address
28.0.0.0
Broadcast address
28.63.255.255
First usable
28.0.0.1
Last usable
28.63.255.254
Usable hosts
4,194,302 (4,194,304 less the network and broadcast addresses)
Subnet mask
255.192.0.0
Wildcard mask
0.63.255.255 (Cisco ACLs, OSPF)
Prefix length
/10
Type
Public public
Old class
A (default /8)
As numbers
Hex 1C000000 · Integer 469762048 to 473956351
Reverse DNS zones
0.28.in-addr.arpa
1.28.in-addr.arpa
2.28.in-addr.arpa
3.28.in-addr.arpa
4.28.in-addr.arpa
5.28.in-addr.arpa
6.28.in-addr.arpa
7.28.in-addr.arpa
8.28.in-addr.arpa
9.28.in-addr.arpa
10.28.in-addr.arpa
11.28.in-addr.arpa
12.28.in-addr.arpa
13.28.in-addr.arpa
14.28.in-addr.arpa
15.28.in-addr.arpa
and 48 more
/10 is not on a 8-bit boundary, so it takes 64 /16 zones.
Binary
Binary view
Binary (network bits bold, host bits grey)Dotted
Address00011100.00000000.00000000.0000000028.0.0.0
Subnet mask11111111.11000000.00000000.00000000255.192.0.0
Network00011100.00000000.00000000.0000000028.0.0.0
Broadcast00011100.00111111.11111111.1111111128.63.255.255
Split into smaller subnets/17
/11 (2)/12 (4)/13 (8)/14 (16)/15 (32)/16 (64)/17 (128)/18 (256)/19 (512)/20 (1,024)/21 (2,048)/22 (4,096)

28.0.0.0/10 makes 128 subnets of /17.

Subnets
#SubnetUsable hosts rangeBroadcastHosts
128.0.0.0/1728.0.0.1 to 28.0.127.25428.0.127.25532,766
228.0.128.0/1728.0.128.1 to 28.0.255.25428.0.255.25532,766
328.1.0.0/1728.1.0.1 to 28.1.127.25428.1.127.25532,766
428.1.128.0/1728.1.128.1 to 28.1.255.25428.1.255.25532,766
528.2.0.0/1728.2.0.1 to 28.2.127.25428.2.127.25532,766
628.2.128.0/1728.2.128.1 to 28.2.255.25428.2.255.25532,766
728.3.0.0/1728.3.0.1 to 28.3.127.25428.3.127.25532,766
828.3.128.0/1728.3.128.1 to 28.3.255.25428.3.255.25532,766
928.4.0.0/1728.4.0.1 to 28.4.127.25428.4.127.25532,766
1028.4.128.0/1728.4.128.1 to 28.4.255.25428.4.255.25532,766
1128.5.0.0/1728.5.0.1 to 28.5.127.25428.5.127.25532,766
1228.5.128.0/1728.5.128.1 to 28.5.255.25428.5.255.25532,766
1328.6.0.0/1728.6.0.1 to 28.6.127.25428.6.127.25532,766
1428.6.128.0/1728.6.128.1 to 28.6.255.25428.6.255.25532,766
1528.7.0.0/1728.7.0.1 to 28.7.127.25428.7.127.25532,766
1628.7.128.0/1728.7.128.1 to 28.7.255.25428.7.255.25532,766
1728.8.0.0/1728.8.0.1 to 28.8.127.25428.8.127.25532,766
1828.8.128.0/1728.8.128.1 to 28.8.255.25428.8.255.25532,766
1928.9.0.0/1728.9.0.1 to 28.9.127.25428.9.127.25532,766
2028.9.128.0/1728.9.128.1 to 28.9.255.25428.9.255.25532,766
2128.10.0.0/1728.10.0.1 to 28.10.127.25428.10.127.25532,766
2228.10.128.0/1728.10.128.1 to 28.10.255.25428.10.255.25532,766
2328.11.0.0/1728.11.0.1 to 28.11.127.25428.11.127.25532,766
2428.11.128.0/1728.11.128.1 to 28.11.255.25428.11.255.25532,766
2528.12.0.0/1728.12.0.1 to 28.12.127.25428.12.127.25532,766
2628.12.128.0/1728.12.128.1 to 28.12.255.25428.12.255.25532,766
2728.13.0.0/1728.13.0.1 to 28.13.127.25428.13.127.25532,766
2828.13.128.0/1728.13.128.1 to 28.13.255.25428.13.255.25532,766
2928.14.0.0/1728.14.0.1 to 28.14.127.25428.14.127.25532,766
3028.14.128.0/1728.14.128.1 to 28.14.255.25428.14.255.25532,766
3128.15.0.0/1728.15.0.1 to 28.15.127.25428.15.127.25532,766
3228.15.128.0/1728.15.128.1 to 28.15.255.25428.15.255.25532,766
3328.16.0.0/1728.16.0.1 to 28.16.127.25428.16.127.25532,766
3428.16.128.0/1728.16.128.1 to 28.16.255.25428.16.255.25532,766
3528.17.0.0/1728.17.0.1 to 28.17.127.25428.17.127.25532,766
3628.17.128.0/1728.17.128.1 to 28.17.255.25428.17.255.25532,766
3728.18.0.0/1728.18.0.1 to 28.18.127.25428.18.127.25532,766
3828.18.128.0/1728.18.128.1 to 28.18.255.25428.18.255.25532,766
3928.19.0.0/1728.19.0.1 to 28.19.127.25428.19.127.25532,766
4028.19.128.0/1728.19.128.1 to 28.19.255.25428.19.255.25532,766
4128.20.0.0/1728.20.0.1 to 28.20.127.25428.20.127.25532,766
4228.20.128.0/1728.20.128.1 to 28.20.255.25428.20.255.25532,766
4328.21.0.0/1728.21.0.1 to 28.21.127.25428.21.127.25532,766
4428.21.128.0/1728.21.128.1 to 28.21.255.25428.21.255.25532,766
4528.22.0.0/1728.22.0.1 to 28.22.127.25428.22.127.25532,766
4628.22.128.0/1728.22.128.1 to 28.22.255.25428.22.255.25532,766
4728.23.0.0/1728.23.0.1 to 28.23.127.25428.23.127.25532,766
4828.23.128.0/1728.23.128.1 to 28.23.255.25428.23.255.25532,766
4928.24.0.0/1728.24.0.1 to 28.24.127.25428.24.127.25532,766
5028.24.128.0/1728.24.128.1 to 28.24.255.25428.24.255.25532,766
5128.25.0.0/1728.25.0.1 to 28.25.127.25428.25.127.25532,766
5228.25.128.0/1728.25.128.1 to 28.25.255.25428.25.255.25532,766
5328.26.0.0/1728.26.0.1 to 28.26.127.25428.26.127.25532,766
5428.26.128.0/1728.26.128.1 to 28.26.255.25428.26.255.25532,766
5528.27.0.0/1728.27.0.1 to 28.27.127.25428.27.127.25532,766
5628.27.128.0/1728.27.128.1 to 28.27.255.25428.27.255.25532,766
5728.28.0.0/1728.28.0.1 to 28.28.127.25428.28.127.25532,766
5828.28.128.0/1728.28.128.1 to 28.28.255.25428.28.255.25532,766
5928.29.0.0/1728.29.0.1 to 28.29.127.25428.29.127.25532,766
6028.29.128.0/1728.29.128.1 to 28.29.255.25428.29.255.25532,766
6128.30.0.0/1728.30.0.1 to 28.30.127.25428.30.127.25532,766
6228.30.128.0/1728.30.128.1 to 28.30.255.25428.30.255.25532,766
6328.31.0.0/1728.31.0.1 to 28.31.127.25428.31.127.25532,766
6428.31.128.0/1728.31.128.1 to 28.31.255.25428.31.255.25532,766
6528.32.0.0/1728.32.0.1 to 28.32.127.25428.32.127.25532,766
6628.32.128.0/1728.32.128.1 to 28.32.255.25428.32.255.25532,766
6728.33.0.0/1728.33.0.1 to 28.33.127.25428.33.127.25532,766
6828.33.128.0/1728.33.128.1 to 28.33.255.25428.33.255.25532,766
6928.34.0.0/1728.34.0.1 to 28.34.127.25428.34.127.25532,766
7028.34.128.0/1728.34.128.1 to 28.34.255.25428.34.255.25532,766
7128.35.0.0/1728.35.0.1 to 28.35.127.25428.35.127.25532,766
7228.35.128.0/1728.35.128.1 to 28.35.255.25428.35.255.25532,766
7328.36.0.0/1728.36.0.1 to 28.36.127.25428.36.127.25532,766
7428.36.128.0/1728.36.128.1 to 28.36.255.25428.36.255.25532,766
7528.37.0.0/1728.37.0.1 to 28.37.127.25428.37.127.25532,766
7628.37.128.0/1728.37.128.1 to 28.37.255.25428.37.255.25532,766
7728.38.0.0/1728.38.0.1 to 28.38.127.25428.38.127.25532,766
7828.38.128.0/1728.38.128.1 to 28.38.255.25428.38.255.25532,766
7928.39.0.0/1728.39.0.1 to 28.39.127.25428.39.127.25532,766
8028.39.128.0/1728.39.128.1 to 28.39.255.25428.39.255.25532,766
8128.40.0.0/1728.40.0.1 to 28.40.127.25428.40.127.25532,766
8228.40.128.0/1728.40.128.1 to 28.40.255.25428.40.255.25532,766
8328.41.0.0/1728.41.0.1 to 28.41.127.25428.41.127.25532,766
8428.41.128.0/1728.41.128.1 to 28.41.255.25428.41.255.25532,766
8528.42.0.0/1728.42.0.1 to 28.42.127.25428.42.127.25532,766
8628.42.128.0/1728.42.128.1 to 28.42.255.25428.42.255.25532,766
8728.43.0.0/1728.43.0.1 to 28.43.127.25428.43.127.25532,766
8828.43.128.0/1728.43.128.1 to 28.43.255.25428.43.255.25532,766
8928.44.0.0/1728.44.0.1 to 28.44.127.25428.44.127.25532,766
9028.44.128.0/1728.44.128.1 to 28.44.255.25428.44.255.25532,766
9128.45.0.0/1728.45.0.1 to 28.45.127.25428.45.127.25532,766
9228.45.128.0/1728.45.128.1 to 28.45.255.25428.45.255.25532,766
9328.46.0.0/1728.46.0.1 to 28.46.127.25428.46.127.25532,766
9428.46.128.0/1728.46.128.1 to 28.46.255.25428.46.255.25532,766
9528.47.0.0/1728.47.0.1 to 28.47.127.25428.47.127.25532,766
9628.47.128.0/1728.47.128.1 to 28.47.255.25428.47.255.25532,766
9728.48.0.0/1728.48.0.1 to 28.48.127.25428.48.127.25532,766
9828.48.128.0/1728.48.128.1 to 28.48.255.25428.48.255.25532,766
9928.49.0.0/1728.49.0.1 to 28.49.127.25428.49.127.25532,766
10028.49.128.0/1728.49.128.1 to 28.49.255.25428.49.255.25532,766
10128.50.0.0/1728.50.0.1 to 28.50.127.25428.50.127.25532,766
10228.50.128.0/1728.50.128.1 to 28.50.255.25428.50.255.25532,766
10328.51.0.0/1728.51.0.1 to 28.51.127.25428.51.127.25532,766
10428.51.128.0/1728.51.128.1 to 28.51.255.25428.51.255.25532,766
10528.52.0.0/1728.52.0.1 to 28.52.127.25428.52.127.25532,766
10628.52.128.0/1728.52.128.1 to 28.52.255.25428.52.255.25532,766
10728.53.0.0/1728.53.0.1 to 28.53.127.25428.53.127.25532,766
10828.53.128.0/1728.53.128.1 to 28.53.255.25428.53.255.25532,766
10928.54.0.0/1728.54.0.1 to 28.54.127.25428.54.127.25532,766
11028.54.128.0/1728.54.128.1 to 28.54.255.25428.54.255.25532,766
11128.55.0.0/1728.55.0.1 to 28.55.127.25428.55.127.25532,766
11228.55.128.0/1728.55.128.1 to 28.55.255.25428.55.255.25532,766
11328.56.0.0/1728.56.0.1 to 28.56.127.25428.56.127.25532,766
11428.56.128.0/1728.56.128.1 to 28.56.255.25428.56.255.25532,766
11528.57.0.0/1728.57.0.1 to 28.57.127.25428.57.127.25532,766
11628.57.128.0/1728.57.128.1 to 28.57.255.25428.57.255.25532,766
11728.58.0.0/1728.58.0.1 to 28.58.127.25428.58.127.25532,766
11828.58.128.0/1728.58.128.1 to 28.58.255.25428.58.255.25532,766
11928.59.0.0/1728.59.0.1 to 28.59.127.25428.59.127.25532,766
12028.59.128.0/1728.59.128.1 to 28.59.255.25428.59.255.25532,766
12128.60.0.0/1728.60.0.1 to 28.60.127.25428.60.127.25532,766
12228.60.128.0/1728.60.128.1 to 28.60.255.25428.60.255.25532,766
12328.61.0.0/1728.61.0.1 to 28.61.127.25428.61.127.25532,766
12428.61.128.0/1728.61.128.1 to 28.61.255.25428.61.255.25532,766
12528.62.0.0/1728.62.0.1 to 28.62.127.25428.62.127.25532,766
12628.62.128.0/1728.62.128.1 to 28.62.255.25428.62.255.25532,766
12728.63.0.0/1728.63.0.1 to 28.63.127.25428.63.127.25532,766
12828.63.128.0/1728.63.128.1 to 28.63.255.25428.63.255.25532,766

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.