Calculate Classless Inter-Domain Routing (CIDR) IPv4 blocks online for free with our CIDR Calculator. Compute netmasks, network addresses, broadcast IPs, usable host ranges, and total host allocations directly inside client browser RAM.
Type an IPv4 address and select a CIDR routing prefix (/0 to /32).
View netmask, network address, broadcast address, and usable host IP ranges.
Check total host count and usable host allocations calculated via bitmath.
Uses 32-bit unsigned bitwise shifting (~0 << (32 - prefix)) to calculate exact network bounds.
Supports standard subnets (/1 to /30), /31 point-to-point links (RFC 3021), and /32 single host routes.
All IP network calculations execute inside client browser memory. Zero network addresses are transmitted over the internet.
Classless Inter-Domain Routing (CIDR) represents IPv4 subnet masks as a prefix length ($/N$). The 32-bit subnet mask is constructed by left-shifting $N$ consecutive 1 bits: $ ext{Mask} = (\sim 0 \ll (32 - N)) \ggg 0$.
The Network Address is computed via bitwise AND ($ ext{IP} \mathbin{\&} ext{Mask}$), while the Broadcast Address is computed by applying the wildcard mask ($ ext{Network} \mid \sim ext{Mask}$). Total hosts equal $2^{32 - N}$, with usable hosts equal to $2^{32 - N} - 2$.
Executing 32-bit unsigned bitwise operations in browser RAM produces instant netmask, range, and host counts with 100% client-side privacy.