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IP Subnet Calculator — CIDR & Mask
Calculate subnet mask, network address, broadcast address, and usable host range from any IP and CIDR.
In this article
Understanding Subnets
A subnet divides a network into smaller segments. The subnet mask determines which bits identify the network vs individual hosts. A /24 (255.255.255.0) allows 254 usable addresses. Each additional CIDR bit halves the host count.
Common Sizes
/32: Single host. /30: 2 hosts (point-to-point). /24: 254 hosts (standard LAN). /16: 65,534 hosts. /8: 16.7M hosts.
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Frequently asked questions
What is a subnet mask?▾
A 32-bit number separating the network portion from the host portion of an IP. 255.255.255.0 (/24) means the first 3 octets are network, the last is hosts — allowing 254 devices.
What does /24 mean?▾
CIDR notation: 24 bits for network prefix = 255.255.255.0 mask = 254 usable hosts. Most common subnet for small networks.
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