Subnet Calculator

Calculate network address, broadcast, usable hosts and subnet mask from IP/CIDR

What is it and how does it work?

A subnet calculator takes an IP address and a CIDR prefix — like 192.168.1.0/24 — and works out everything that defines the network: the network address, the broadcast address, the subnet mask, and the range of usable host addresses with how many there are. Subnetting splits an IP range into smaller networks, and the maths behind it is binary and easy to get wrong by hand, because the boundaries fall on bit positions, not the friendly decimal numbers we read.

The CIDR number is the key: it says how many bits at the front of the address are fixed as the network portion, leaving the rest for hosts. A /24 fixes 24 bits and leaves 8 for hosts, giving 256 addresses (254 usable after the network and broadcast are reserved). This tool does the binary arithmetic instantly, so you can plan an addressing scheme, check whether two addresses sit in the same subnet, or size a network for a needed number of hosts — without converting to binary in your head. Everything runs in your browser.

Common use cases

• Planning a network: enter an IP and CIDR to see the usable host range and how many devices the subnet supports.
• Checking if two IPs share a subnet: confirm whether two addresses fall within the same network range.
• Sizing a subnet: work out which prefix length gives enough usable hosts for a given number of devices.

Frequently asked questions

What does the /24 in an address mean?

The number after the slash is the CIDR prefix — how many leading bits define the network portion of the address. A /24 means the first 24 bits are the network and the remaining 8 are for hosts, which corresponds to the subnet mask 255.255.255.0.

Why are there two fewer usable hosts than total addresses?

Each subnet reserves two addresses: the network address (all host bits 0) identifies the subnet itself, and the broadcast address (all host bits 1) reaches every host at once. Neither can be assigned to a device, so usable hosts are total addresses minus two.

What is the difference between the network and broadcast address?

The network address is the first address in the range and names the subnet; the broadcast address is the last and is used to send to all hosts on that subnet simultaneously. The usable host addresses are all the ones in between.

How do I know if two addresses are on the same subnet?

Apply the subnet mask to both addresses: if they produce the same network address, they are on the same subnet and can communicate directly. This calculator shows the network address, so you can compare it for any two IPs with the same mask.

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