Subnet Calculator
The subnet calculator takes any IPv4 address and CIDR prefix (for example 192.168.1.0/24) and returns the full breakdown of that subnet: the network address, broadcast address, dotted-decimal subnet mask, the usable IP range, and the total number of hosts.
It is the fastest way to answer the questions that come up constantly when planning IP space: does this /26 fit 50 devices, where does the range start and end, and what is the broadcast address. Paste an address, pick a prefix, and the results update as you type.
Subnet Calculator
Calculate network address, broadcast, usable range, and host count from an IP and CIDR prefix.
Enter values above to see results.
Frequently Asked Questions
How do I calculate usable hosts in a subnet?
Take the total number of addresses in the subnet (2^(32 - prefix)) and subtract two for the network and broadcast addresses. For example, a /24 has 256 addresses, so it offers 254 usable host addresses.
What is the difference between a network and broadcast address?
The network address is the first address in a subnet and identifies the subnet itself; the broadcast address is the last address and is used to reach every host on the subnet at once. Neither can be assigned to a device.
Read More
Guides that go deeper on the same topic.
Subnetting Guide for Network Engineers
A practical subnetting guide for network engineers covering CIDR notation, subnet plan design, VLAN and VRF mapping, common pitfalls, and tools for keeping your IP space organized at scale.
IP Planning: The Complete Guide, Tools, and Best Practices
Your network grows every week, and so does the number of IP addresses you need to track. This guide covers IP planning best practices, core concepts, and how to choose the right approach for your team.
IP Address Management Best Practices in 2026
IP address management has evolved beyond simple spreadsheets. Learn the key practices, tooling decisions, and operational patterns that define modern IPAM in 2026.
More Tools
Explore the other tools in the toolkit.
CIDR Calculator
Free CIDR calculator: convert any prefix length from /0 to /32 into its dotted-decimal subnet mask, binary mask, wildcard mask, and total usable hosts.
IPv4 Range Calculator
Free IPv4 range calculator: enter a start and end IP address to find the smallest set of CIDR blocks covering the range, plus the total number of addresses.
VLAN Capacity Calculator
Free VLAN capacity calculator: determine the subnet size you need for your number of VLANs and devices per VLAN, including growth headroom.
Rack Power Calculator
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BTU Calculator
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Subnet Overlap Checker
Free subnet overlap checker: paste a list of CIDR blocks and instantly see every pair that shares addresses, before conflicts cause routing or IP assignment problems.
IPv6 Subnet Calculator
Free IPv6 subnet calculator: enter an IPv6 address and prefix length to get the network address, expanded form, total addresses, and the number of /64 subnets.
Batch CIDR Converter
Free batch CIDR converter: paste a list of subnets as CIDR, IP + mask, or bare IP and convert them all to network address, subnet mask, usable range, and host count in one click.
IP Allocation Planner
Free IP allocation planner: assign CIDR blocks inside a supernet to sites, VLANs, or teams and see used, free, and overlapping address space instantly.