CIDR & Subnet Calculator
Enter any IPv4 CIDR notation and this subnet calculator free tool instantly works out the network address, broadcast address, subnet mask, and usable host range.
Not sure which prefix to use? Enter how many usable hosts you need and get the smallest matching subnet.
About the CIDR & Subnet Calculator
Classless Inter-Domain Routing, or CIDR, notation compresses a subnet mask and an IP address into a single compact string like 192.168.1.0/24. This CIDR calculator online tool parses that notation with pure binary math, then works out the subnet mask, wildcard mask, network address, and broadcast address so you do not have to do the arithmetic by hand.
It also reports the usable host range, correctly handling the special /31 point-to-point and /32 host routes instead of subtracting two hosts blindly, along with an informational IP class and whether the address falls inside a private range like 10.0.0.0/8, 172.16.0.0/12, or 192.168.0.0/16. This release covers IPv4 only and does not calculate IPv6 prefixes.
How to Use
- Enter an IPv4 address with its prefix length, such as
10.0.0.0/16, into the CIDR Notation field. - Click Calculate to see the subnet mask, wildcard mask, network and broadcast addresses, and usable host range.
- Check the IP class and address scope to confirm whether the block is public or a private network.
- Need help sizing a subnet instead? Enter a host count into Hosts Needed and click Suggest Subnet for the smallest matching prefix.
Why Use This Subnet Calculator
Correct Edge Case Handling
/31 point-to-point links and /32 host routes are handled per standard networking convention instead of producing negative or zero host counts.
Accurate 32-bit Math
Every calculation uses unsigned 32-bit integer arithmetic, so large masks and network ranges never produce negative-number bugs.
Reverse Subnet Sizing
Enter the number of hosts you need and instantly get the tightest CIDR prefix that fits, avoiding wasted address space.
Runs in Your Browser
Every address you enter is calculated locally on your device, ideal for internal network ranges you would rather not send anywhere.
Who Should Use This Tool
- Network engineers planning a network address calculator lookup before allocating address blocks across sites.
- System administrators configuring firewalls, routers, or VPCs who need an exact subnet mask and broadcast address.
- Cloud and DevOps engineers sizing VPC or subnet CIDR blocks in AWS, Azure, or GCP without wasting address space.
- Students and certification candidates using a cidr to ip range converter to check subnetting homework and practice exam questions.
Privacy first. No address you enter into this tool is ever uploaded, logged, or stored on a server. All calculations happen directly on your device inside your browser tab.