ip address range calculator

IPv4 Address (or CIDR notation)

You can enter plain IP or IP/CIDR in one field.

Prefix Length (CIDR)

Valid range: 0 to 32

What this IP address range calculator does

This tool calculates the full IPv4 subnet details from an IP address and prefix length. In one click, you get the network address, broadcast address, first usable host, last usable host, subnet mask, wildcard mask, total addresses, and usable hosts.

It is useful for network planning, firewall rules, VLAN design, DHCP scope checks, and troubleshooting overlap issues between subnets.

Why IP ranges matter

Every device on a network needs an address. Subnetting divides large networks into smaller ranges so traffic can be managed more efficiently. Understanding the usable address range helps avoid conflicts and helps ensure routers, switches, and servers are configured correctly.

Prevents assigning network or broadcast addresses to hosts
Helps size subnets correctly for growth
Improves route summarization and network performance
Supports cleaner segmentation and security policies

Quick subnet reference

Common prefixes

/24 → 256 total, 254 usable (typical small LAN)
/25 → 128 total, 126 usable
/26 → 64 total, 62 usable
/27 → 32 total, 30 usable
/28 → 16 total, 14 usable
/30 → 4 total, 2 usable (legacy point-to-point)
/31 → 2 total, 2 usable (modern point-to-point)
/32 → 1 total, single host route

How calculation works (simple explanation)

1) Convert prefix to subnet mask

A prefix such as /24 means the first 24 bits are network bits. That produces subnet mask 255.255.255.0.

2) Find network address

The network address is computed using a bitwise AND between the IP and subnet mask.

3) Find broadcast address

The broadcast address is the highest address in the subnet. It is computed by setting all host bits to 1.

4) Determine host range

For most subnets, usable hosts are between network+1 and broadcast-1. Special handling applies to /31 and /32.

Tip: If you enter CIDR format like 10.20.30.40/20, the calculator will automatically read the prefix.

Practical examples

Office VLAN example

Input 192.168.50.77 and /26. You can instantly identify the exact block and assign DHCP safely without stepping into another VLAN.

Firewall allow-list example

Need to permit a whole subnet? Use the network and broadcast output to verify your CIDR before building ACL rules.

Common mistakes to avoid

Using the network address for a host
Using the broadcast address for a host
Mixing up /24 with 255.255.255.0 incorrectly
Assuming every subnet always has 2 unusable addresses (not true for /31 and /32)

FAQ

Does this support IPv6?

This page is focused on IPv4 range calculations. IPv6 uses a different addressing model and notation.

What if I only know CIDR notation?

Enter the full value directly in the IP field, like 172.16.4.20/22. The prefix field can remain blank.

Can I use this for cloud networks?

Yes. The math is the same for AWS, Azure, GCP, on-prem, or hybrid environments.