Subnet Calculator
Subnet Calculator find network broadcast address cidr host range ipv4 subnet maskInspect an offline IPv4 CIDR block
Enter a dotted-decimal IPv4 address and a prefix from 0 through 32. The tool applies the mask locally and reports the containing network, broadcast address, total size, and traditional host range.
What a CIDR prefix means
IPv4 addresses contain 32 bits. A /24 prefix assigns the first 24 bits to the network and leaves eight bits for addresses within that block. A longer prefix creates a smaller block; a shorter prefix creates a larger one. The dotted subnet mask shows the same boundary in another notation.
Calculation method
The address is converted into one unsigned 32-bit value. Network bits are retained while host bits are cleared to find the network address. Setting all host bits finds the broadcast address. The block contains two raised to the number of host bits total addresses.
Worked example
For 192.168.1.130/24, the mask is 255.255.255.0. The containing network is 192.168.1.0 and the broadcast address is 192.168.1.255. Under traditional subnetting, host addresses run from 192.168.1.1 through 192.168.1.254.
Special /31 and /32 prefixes
A /31 contains two addresses and has no traditional network-and-broadcast-separated host range; it can be used on certain point-to-point links under modern conventions. A /32 identifies one address. The page reports these explicitly instead of subtracting two and displaying a negative host count.
Private-looking addresses are not verified connectivity
The calculator performs arithmetic only. It does not contact the address, inspect interfaces, identify ownership, confirm routing, scan ports, or determine whether an address is public, private, assigned, reachable, or safe. Actual network configuration may use routes and policies beyond this block.
Security and limitations
This is IPv4-only and accepts canonical four-octet dotted decimal. It does not calculate IPv6, wildcard masks, variable-length subnet plans, route aggregation, VLANs, DHCP pools, gateways, reserved infrastructure addresses, or firewall rules. Have a network administrator review production changes.
Subnet Calculator FAQ
Does the entered address need to be the network address?
No. Any address in the block can be entered; the tool finds its network.
Why are two addresses normally excluded?
Traditional IPv4 subnets reserve the all-zero host value for the network and the all-one value for broadcast.
Does this reveal my current IP address?
No. It only processes the address you type.