Subnet netmask calculator - supports IPv4 and IPv6, subnet splitting, CSV export, and reverse lookup
Subnet Calculator
Free IP CIDR Calculator & Subnet Mask Tool for IPv4 and IPv6
IPv4
IPv6
Dark
Light
Calculator
Reverse lookup
Dotted decimal
CIDR
IP ADDRESS
SUBNET MASK
CIDR
Calculate
BINARY REPRESENTATION
network bits
host bits
SUBNET SPLITTER
NEW PREFIX LENGTH
Split
SUBNET MASK OR PREFIX (e.g. 255.255.0.0, /16, or 16)
Look up
FULL REFERENCE TABLE
Calculator
Reverse lookup
IPV6 ADDRESS / PREFIX
Calculate
BINARY REPRESENTATION (first 64 bits)
network bits
host bits
SUBNET SPLITTER
NEW PREFIX LENGTH
Split
PREFIX LENGTH (e.g. /48 or 48)
Look up
COMMON PREFIX REFERENCE