CIDR Calculator

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Type an IPv4 address and prefix (e.g. 10.0.0.0/24), or drag the slider. Everything below recomputes instantly — network and broadcast addresses, the usable host range, masks, a bit-by-bit view of the network/host boundary, equal-subnet splitting, and an address-membership check. All client-side; nothing is sent anywhere.

Address / prefix

/24

Binary · network vs host bits

Each bit of the address and mask, grouped into four octets. The glowing divider marks the prefix boundary — teal bits belong to the network, indigo bits address the host.

Mask

Split into equal subnets

Carve the current network into a power-of-two number of equal subnets, each one prefix longer.

Divide into

Which subnet does an address belong to?

Enter any IPv4 address to see which subnet (at the current prefix) it falls into, and whether it's inside the base network.

Address to check

All arithmetic is unsigned 32-bit integer math, computed locally in your browser. /31 is treated as an RFC 3021 point-to-point link (both addresses usable) and /32 as a single host route.