Why are two addresses in a subnet not usable?

The first address is the network identifier and the last is the broadcast address, so a /24 has 256 total but 254 assignable to devices. That's why host counts are always two fewer than the block size (for IPv4).

Is any network data sent anywhere?

No. The calculation is pure math done locally in your browser, so the addresses you enter never leave your device.

IP Subnet Calculator

Calculate network address, broadcast, subnet mask and usable IPs.

IP Address

CIDR (Netmask)/24

Mask: 255.255.255.0

Network Class

Private Network

Network Address

192.168.1.0

Broadcast Address

192.168.1.255

Subnet Mask

255.255.255.0

Wildcard Mask

0.0.0.255

First Usable IP

192.168.1.1

Last Usable IP

192.168.1.254

Usable Hosts254

Total IPs: 256

Binary Visualization

IP Address11000000.10101000.00000001.00000001

Subnet Mask11111111.11111111.11111111.00000000

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Calculating IP Subnets and CIDR Ranges

Overview

A subnet calculator takes an IP address and a subnet mask (or CIDR prefix like /24) and works out the network's key numbers: the network address, broadcast address, usable host range, and how many devices fit. This saves you the error-prone binary math when planning or troubleshooting a network. It computes everything instantly in your browser, with nothing sent to a server.

How to Use (Step by Step)

1
Enter the IP and mask
Type an IP address and a subnet mask or CIDR prefix like /24.
2
Calculate the subnet
The tool derives the network address, broadcast, usable host range, and host count.
3
Apply the results
Use the ranges to configure devices, plan address space, or verify connectivity.

How It Works

You enter an IP and a mask, in either dotted form (255.255.255.0) or CIDR (/24). The tool converts them to binary internally, applies the mask to find the network and broadcast addresses, and derives the first and last usable host addresses and the total host count. It handles IPv4 (and often IPv6) and shows the results in a readable table — all computed locally.

When to Use This

Planning how to split a network into subnets of the right size. Finding the usable IP range for a given CIDR block. Checking whether two addresses are on the same subnet. Configuring a router, firewall, or DHCP scope. Studying for a networking certification. Troubleshooting why a device can't reach another on the LAN.

Frequently Asked Questions

It's the number of bits fixed for the network portion. /24 means the first 24 bits identify the network, leaving 8 bits (256 addresses, 254 usable) for hosts. A smaller number means a larger network.

Important Notes

Subnetting rules differ between IPv4 and IPv6, and point-to-point links (/31) or single hosts (/32) are special cases. Double-check the mask matches your intent before applying it to live equipment.