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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:

IP/Netmask bits: /


Usable addresses:
First usable:
Last usable:

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)

result: /

Subnet Mask Converter (bits format to dotted decimal)



Number of required addresses to netmask converter

number of addresses needed:


mask: / dotted dec. mask:
usable amount of addresses:

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



Convert hex IP-address or mask dotted decimal


dotted decimal:

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


Convert a Network Mask to amount of usable addresses

Mask: /


Usable amount of addr: Total number of addr:
Netmaks in dotted decimal format:

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". - Well-known multicast addresses, control channels - Globally-scoped (Internet-wide) multicast addresses - 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): - A 24-bit block, /8, class A network - A 20-bit block, /12, set of 16 contiguous class B network numbers - A 16-bit block, /16, set of 255 contiguous class C network numbers

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

Overview of common subnets and masks

Mask Hosts  Usable Netmask          Hex Mask
/30  4      2  fffffffc  this is 1/64 of a Class C net
/29  8      6  fffffff8  this is 1/32 of a Class C net
/28  16     14  fffffff0  this is 1/16 of a Class C net
/27  32     30  ffffffe0  this is 1/8 of a Class C net
/26  64     62  ffffffc0  this is 1/4 of a Class C net
/24  256    254    ffffff00  this is a Class C net
/23  512    510    fffffe00  these are 2 Class C net
/22  1024   1022    fffffc00  these are 4 Class C net
/21  2048   2046    fffff800  these are 8 Class C net
/20  4096   4094    fffff000  these are 16 Class C net
/19  8192   8190    ffffe000  these are 32 Class C net
/18  16384  16382    ffffc000  these are 64 Class C net
/17  32768  32766    ffff8000  these are 128 Class C net
/16  65536  65534      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)

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