What is CIDR notation?

CIDR notation writes an IPv4 address with a slash and a prefix length, such as 192.168.1.0/24. The number after the slash is how many bits belong to the network portion; the rest are host bits.

How do I calculate a /24 network?

A /24 uses 24 network bits and 8 host bits. Enter 192.168.1.0/24 in this calculator to see mask 255.255.255.0, network 192.168.1.0, broadcast 192.168.1.255, and 254 usable hosts.

How many hosts are in a /24 subnet?

A /24 has 256 total addresses. After you reserve the network and broadcast addresses, 254 usable hosts remain.

How do I convert CIDR to a subnet mask?

Write prefix-length ones from the left, fill the rest with zeros, then convert each octet to decimal. /24 becomes 255.255.255.0. This tool shows the dotted mask and binary mask together so you can check your conversion.

Can I calculate IPv4 network and broadcast addresses?

Yes. Enter any valid IPv4 CIDR string and the calculator returns the network address, broadcast address, and usable host range for that block.

What is CIDR Calculator?

A CIDR calculator takes an IPv4 address written with a prefix (for example 10.0.0.0/8) and works out the matching subnet mask, host counts, and network boundaries. This one is free and runs in your browser.

How does the CIDR Calculator work?

It reads the prefix length, builds the matching 32-bit mask, applies that mask to the address to find the network ID, then derives broadcast, usable range, and host counts from the remaining host bits.

How do I use the CIDR Calculator?

Type an address with a slash prefix such as 172.16.0.0/12, or pick an example button. Results update as you type, no account and no download.

Is this CIDR Calculator free to use?

Yes. It is free for beginners, CCNA students, network engineers, and anyone practising subnetting. No sign-up is required.

Can I use the CIDR Calculator on mobile?

Yes. The page works in a mobile browser, so you can check CIDR maths on a phone or tablet as well as on a desktop.

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Networking

CIDR Calculator

Free online CIDR calculator for beginners, CCNA students, and network engineers. Enter IPv4 CIDR notation to get subnet mask, network, broadcast, and usable hosts.

Runs in your browser — your data stays on your device

Free tool

CIDR notation looks simple, just a slash and a number, but that prefix decides your network size, your host count, and where the broadcast address sits. This free CIDR calculator is built for people who need a clear answer fast: paste an address such as 192.168.1.0/24 and read the subnet mask, network ID, broadcast, usable range, binary mask, and host maths in one place. We use the same workflow in class when CCNA students check subnetting practice before they trust a live config.

How to use the CIDR Calculator

1
Enter an IPv4 address with CIDR notation in one field, for example 192.168.1.0/24 or 10.0.0.0/8.
2
Or tap one of the example buttons to load a common home-network or lab prefix.
3
Read the results: CIDR prefix, dotted subnet mask, binary mask, network and broadcast addresses, usable hosts, and total addresses.

Why a dedicated CIDR calculator helps

Routing tables, firewall rules, cloud VPCs, and Cisco exam questions all speak in CIDR. Beginners often convert /24 correctly and then stall on /26 or /30. Network engineers still double-check unusual prefixes before they push a change. This tool keeps the focus on CIDR notation itself: one string in, full IPv4 picture out, so you can practise subnetting for home networks, IT coursework, or network administration without switching between formats mid-thought.

IPv4 CIDR example

Try 192.168.10.0/26. The calculator returns mask 255.255.255.192, network 192.168.10.0, broadcast 192.168.10.63, and 62 usable hosts (192.168.10.1-192.168.10.62). That is a classic CCNA-style block: small enough to force careful host-bit counting, common enough that you will see it in labs and on Cisco networking exams.

Guides and next steps

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This CIDR calculator runs locally in your browser. Nothing you type is sent to our servers.

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