Subnet Calculator

By the 19216811 Editorial Team · Updated August 2026

This free subnet calculator turns any IPv4 address and CIDR prefix into a full network breakdown. Enter an address, pick a mask, and get the network, broadcast, host range, and more instantly.

It works as a CIDR calculator too. Switch the prefix from /0 to /32 and every result updates in real time, with copy buttons for each value. No sign-up, no limits.

How to Use This Subnet Calculator

Get a full subnet breakdown in three quick steps.

1. Type an IPv4 address, such as 192.168.1.10.
2. Choose a CIDR prefix or subnet mask.
3. Read the results and copy any value.

What Is a Subnet Calculator?

A subnet calculator works out the structure of an IP network from one address and a mask. Instead of doing binary math by hand, you get every address and range in seconds.

Network admins use it to plan address space, split networks, and avoid overlaps. Students use it to check subnetting homework. Anyone setting up a router can use it to understand their LAN.

What Is CIDR Notation?

CIDR notation writes a network as an address plus a slash and a number, like 192.168.1.0/24. The number is the prefix length: how many bits are fixed for the network part.

A larger prefix means a smaller network. A /24 leaves 8 host bits, giving 254 usable hosts. A /30 leaves 2 host bits, giving just 2. Use this CIDR calculator to see the numbers.

A few common prefixes show how CIDR notation maps to a subnet mask and host count. This table lists the ones you will meet most often on home and office networks.

CIDR	Subnet mask	Usable hosts	Typical use
/24	255.255.255.0	254	Standard home or office network
/25	255.255.255.128	126	Half of a class C block
/26	255.255.255.192	62	Small department or subnet
/27	255.255.255.224	30	Small office or lab group
/28	255.255.255.240	14	Tiny subnet or DMZ
/30	255.255.255.252	2	Point-to-point router link

The usable host count is always two fewer than the total, because each subnet reserves a network and a broadcast address.

Subnet Mask and Wildcard Mask

The subnet mask marks which bits are the network. In 255.255.255.0, the first three groups are fixed and the last is free for hosts. The wildcard mask is simply its inverse.

Wildcard masks appear in firewall and access-list rules, where 0 means match and 255 means ignore. This subnet calculator shows both the mask and its wildcard, so you never convert by hand.

CIDR Notation Chart (/0 to /32)

This complete chart maps every CIDR prefix from /0 to /32 to its subnet mask, wildcard mask, total addresses, and usable hosts. It is a handy reference for any IP subnetting calculator task.

Prefixes /31 and /32 are special: /31 gives two point-to-point hosts, and /32 identifies a single address.

Public, Private, and Special IP Ranges

Not every address is routable on the internet. Some blocks are reserved for private networks, loopback, and link-local use. The calculator labels each address so you know its type at a glance.

These reserved ranges show up constantly in subnetting work. Keep them in mind, because a private address behind a router is normal, while a public one is reachable across the internet.

Range	CIDR	Common use	Routable on internet
10.0.0.0	/8	Large private networks	No, private only
172.16.0.0	/12	Medium business networks	No, private only
192.168.0.0	/16	Home and office LAN addresses	No, private only
127.0.0.0	/8	Loopback to this device	No, local only
169.254.0.0	/16	Link-local when DHCP fails	No, single link

If the calculator labels your address as private, it lives behind a router and cannot be reached directly from the internet.

Worked Example: Subnetting 192.168.1.0/24

Say you have 192.168.1.0/24 and need four smaller subnets. Borrow two host bits to make /26 blocks. Each /26 then holds 62 usable hosts, which is plenty for a small team.

The four /26 subnets break down like this.

• First subnet: 192.168.1.0 to 192.168.1.63.
• Second subnet: 192.168.1.64 to 192.168.1.127.
• Third subnet: 192.168.1.128 to 192.168.1.191.
• Fourth subnet: 192.168.1.192 to 192.168.1.255.

Plug any of these into the calculator above to confirm the network, broadcast, and host range. It is the fastest way to check your subnetting before you configure a router.

Frequently Asked Questions

What is a subnet calculator used for?

It converts an IP address and subnet mask into the network address, broadcast address, usable host range, and host count. It saves you from doing binary subnetting math by hand.

Is this a CIDR calculator too?

Yes. Pick any prefix from /0 to /32 and it works as a CIDR calculator. It shows the CIDR notation, subnet mask, and wildcard mask for the block you enter.

How many usable hosts are in a /24?

A /24 has 256 total addresses and 254 usable hosts. The network keeps one address for itself and one for broadcast, leaving 254 for devices.

What is CIDR notation?

CIDR notation writes a network as an address and a prefix length, like 10.0.0.0/8. The prefix counts the network bits. This CIDR notation calculator turns that into full details.

Does it support IPv6?

This tool focuses on IPv4, which covers most home and office subnetting. IPv6 uses much larger prefixes and a different format, so it needs a separate calculator.

Is my data sent anywhere?

No. All subnetting math runs in your browser. Nothing you type is uploaded or stored, so you can use this IP subnetting calculator on private network plans safely.

Related Tools and Guides

Explore more free tools and guides on the site.

• What Is My IP Address tool
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• Default Router Passwords
• 192.168.1.1 Admin Login
• Router Brand Login guides

Bottom Line

This subnet calculator gives you the full picture of any IPv4 block in one place. Use it as a CIDR calculator, a subnetting checker, or a quick reference whenever you plan a network.