Web Network, IP Address, and Hex Calculators and Notes

June, 2020

Want to convert from hexadecimal to binary? Or convert between dotted IP address format and hex? Or find out a CIDR notation IP address range? The tools on this page, all created in Javascript, will do all this and more. Give them a try. IPv6 notes included, but read on for simple methods that obviate an ipv6 subnet calculator.

Network and IPv4 address (CIDR) calculator

IPv6 Notes Below
Show network, broadcast, first and last address for a given network:

The netmask in "bits format" is also known as mask in CIDR format (CIDR=Classless Inter-Domain Routing). Output here equivalent to whatmask.

Converters for Network and IP address

Subnet Mask Converter (dotted decimal to bits format)

Subnet Mask Converter (bits format to dotted decimal)

Number of required addresses to netmask converter

Convert dotted decimal IP-address or mask to binary and hex

Convert hex IP-address or mask dotted decimal

Calculate the bit-complement of an IP-address (invert)

Convert a Network Mask to amount of usable addresses

Convert decimal to binary and hex

Convert binary to decimal and hex

Convert hex to decimal and binary

IP Multicast address ranges

All multicast addresses can easily be recognized because they start with the bit pattern "1110".

224.0.0.0 - 224.0.0.255 Well-known multicast addresses, control channels
224.0.1.0 - 238.255.255.255 Globally-scoped (Internet-wide) multicast addresses
239.0.0.0 - 239.255.255.255 Local multicast addresses

Special and private address ranges

Private address ranges are not routed on the Internet and can be freely allocated in any private network. NAT (network address translation) is required when connecting such a network to the Internet.

Private network addresses (RFC1597/RFC1918 addresses):
10.0.0.0 - 10.255.255.255 A 24-bit block, /8, class A network
172.16.0.0 - 172.31.255.255 A 20-bit block, /12, set of 16 contiguous class B network numbers
192.168.0.0 - 192.168.255.255 A 16-bit block, /16, set of 255 contiguous class C network numbers

Special addresses:
127.0.0.0 - 127.255.255.255 Special address range for the localhost. You can normally not use those addresses for anything else. 127.0.0.1 is generally assigned to the loopback device
0.0.0.0 Special host address commonly reserved for the default route

Overview of common subnets and masks

Mask Hosts  Usable Netmask          Hex Mask
/30  4      2      255.255.255.252  fffffffc  this is 1/64 of a Class C net
/29  8      6      255.255.255.248  fffffff8  this is 1/32 of a Class C net
/28  16     14     255.255.255.240  fffffff0  this is 1/16 of a Class C net
/27  32     30     255.255.255.224  ffffffe0  this is 1/8 of a Class C net
/26  64     62     255.255.255.192  ffffffc0  this is 1/4 of a Class C net
/24  256    254    255.255.255.0    ffffff00  this is a Class C net
/23  512    510    255.255.254.0    fffffe00  these are 2 Class C net
/22  1024   1022   255.255.252.0    fffffc00  these are 4 Class C net
/21  2048   2046   255.255.248.0    fffff800  these are 8 Class C net
/20  4096   4094   255.255.240.0    fffff000  these are 16 Class C net
/19  8192   8190   255.255.224.0    ffffe000  these are 32 Class C net
/18  16384  16382  255.255.192.0    ffffc000  these are 64 Class C net
/17  32768  32766  255.255.128.0    ffff8000  these are 128 Class C net
/16  65536  65534  255.255.0.0      ffff0000  these are 256 Class C net = Class B net

IPv6 common netmasks

Subnet calculators are often not required, since IPv6 uses hexadecimal. As long as the prefix length is a multiple of 4, it becomes easy.

Mask Prefix                                   Addresses   /64
/128 2400:111a:9999:0001:222b:1113:444f:9999  1
/64  2400:111a:9999:0001:XXXX:XXXX:XXXX:XXXX  16E          1
/56  2400:111a:9999:11XX:XXXX:XXXX:XXXX:XXXX  4Z          256
/32  2400:111a:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX  65536Y      4G

Units based on IEC 60027-2: 
G = 1,073,741,824;  E = 1,152,921,504,606,846,976; 
Y = 1,208,925,819,614,629,174,706,176; 
Z = 1,180,591,620,717,411,303,424;

Special and private IPv6 addresses

::1/128 localhost
fe80::/10 link local
fc00::/7 unique local unicast (RFC 4193)
fc00::/8 routed internally to a site (RFC 4193)
fd00::/8 free for all, routed internally to a site (RFC 4193)
ff00::/8 multicast
2000::/3 global unicast
2001::/16 /32 subnets for providers, from which /48, /56, /64 are to the customer
2001:db8::/32 reserved for use in documentation
2001:678::/29 provider independent (PI) addressess and TLD nameservers
2002::/16 6to4 scope (RFC 3068)