Subnet Calculator

Network, broadcast, host range and mask for any IPv4 block.

Free
No signup
Nothing uploaded
No watermark

IP address with a prefix or a mask

Network

192.168.1.128

Broadcast

192.168.1.191

Usable hosts

Subnet mask

255.255.255.192

Address: 192.168.1.130
Prefix: /26
Host range: 192.168.1.129 – 192.168.1.190
Wildcard mask: 0.0.0.63used by Cisco ACLs — the inverse of the subnet mask
Total addresses: 64
Address class: Chistorical — classless routing replaced this in 1993
Scope: Private (RFC 1918) — the usual home router range
Address in binary: 11000000.10101000.00000001.10000010
Mask in binary: 11111111.11111111.11111111.11000000

Split this block into smaller subnets

How to Calculate a Subnet From an IP Address

Setting up an office network, a cloud VPC or a lab for a CCNA exam means answering the same questions again and again. Which address is the network? Which is the broadcast? How many devices fit? What range can DHCP hand out?

Type an IPv4 address with a prefix, such as 192.168.1.130/26, or an address followed by a mask. Every answer appears at once, and you can split the block into smaller subnets with one choice from a menu.

No software to install Free Works on any device

Steps to Work Out a Subnet

1

1. Enter the address

Type something like 10.0.0.1/8, or an address and mask like 192.168.1.10 255.255.255.0. Or tap one of the example chips under the box.
2

2. Read the four headline boxes

Network, Broadcast, Usable hosts and Subnet mask appear at the top, with the full host range underneath.
3

3. Check the detail rows

The prefix, wildcard mask, total addresses, historical class, scope and both values in binary are listed below.
4

4. Split it if you need to

Choose a longer prefix from the split menu to see each smaller subnet with its usable range and broadcast address.

Try it now

What Does a Subnet Calculator Do?

A subnet is a slice of an IP network. The prefix length, or the matching subnet mask, decides where the network part of an address ends and the host part begins. From that one number you can work out the first and last address, how many hosts fit, and where the block starts.

This calculator does that arithmetic on the address itself. Nothing is looked up on the internet, which is why it works on private ranges and on networks you have not built yet.

Why Use IP and Network Calculators?

Subnet masks, CIDR ranges and download times all come down to binary maths that is easy to slip on. These calculators do the sums in the page, so you can plan an address range or check a speed claim with confidence.

“One wrong subnet mask can take a whole office offline.”

Subnets worked out instantly
CIDR ranges made clear
Download times estimated
Browser details revealed

Usable host counts shown
IPv4 and IPv6 conversions
MAC addresses checked
No commands to install

Popular Uses for Subnet Calculators

Network jobs at home and at work often start with one of these sums.

Planning an office network Split an address block into subnets for each floor, team or guest WiFi.
Reading CIDR notation See the first address, last address and host count behind a range like /24.
Download estimates Work out how long a large file will take on a given connection speed.
Speed claims Turn megabits per second into megabytes to see what a plan really delivers.
Device lookups Find the maker of a network card from its MAC address prefix.
Browser checks See your user agent and browser details when a support team asks.
WebSocket tests Connect to a WebSocket endpoint and watch messages go back and forth.
IPv6 planning Convert an IPv4 address into IPv6 form while preparing a migration.

What This IPv4 Subnet Tool Covers

Correct /31 and /32 handling

A /31 point-to-point link shows two usable addresses and a /32 shows one host, instead of the zero many calculators print.

Scope labelling

Private RFC 1918 ranges, loopback, link-local, carrier-grade NAT and documentation ranges are named, and public addresses are flagged.

Subnet splitting

Divide a block into up to eight bits more of prefix, with the first 64 resulting subnets listed in a table.

Clear error messages

An invalid mask such as 255.255.0.255 is rejected with a plain explanation of what a real mask looks like.

Why Use ToolXkit for Subnet Calculator?

Your files stay with you

Everything runs inside your browser. Nothing you open or type is uploaded to a server.

Network Tools for Different Users

Network administrators

Plan subnets, check CIDR ranges and size links for expected bandwidth.

Networking students

Practise subnetting for CCNA and other exams, and check answers quickly.

Developers

Test WebSocket servers, parse user agents and inspect TCP header fields.

IT support staff

Collect browser details and estimate transfer times while helping users.

Small office owners

Understand router settings and IP ranges without calling a technician every time.

Streamers and gamers

Check upload speed, latency and packet loss figures before a stream.

Best Times to Work Out a Subnet

Network calculators help when you are:

Setting up a new router
Studying for a networking exam
Adding a guest WiFi network
Estimating a large upload
Comparing broadband plans
Identifying an unknown device
Moving to IPv6
Debugging a WebSocket connection

Tips for Planning Subnets

Leave room to grow. If a floor needs 50 devices today, a /26 with 62 usable addresses is tight; a /25 gives you 126.
Keep the network and broadcast addresses out of your DHCP pool. Hand out addresses from the usable host range only.
For home and office networks, stay inside 10.0.0.0/8, 172.16.0.0/12 or 192.168.0.0/16. The scope row confirms when you are.
Studying for an exam? Compare the binary address with the binary mask to see exactly which bits belong to the network.
When splitting a block for VLANs, write down each subnet from the table before assigning any, so ranges never overlap.

Frequently Asked Questions

Answers to common questions about this tool.

How many usable hosts are in a /24?

254. A /24 has 256 addresses in total, and the first is the network address while the last is the broadcast, leaving 254 for devices. Type any address ending in /24 and the Usable hosts box shows the same answer.

What is a wildcard mask used for?

It is the subnet mask with every bit flipped, so 255.255.255.0 becomes 0.0.0.255. Cisco access control lists and OSPF network statements use it to say which bits of an address must match.

Can I type a subnet mask instead of a prefix?

Yes. Type the address, a space, then the mask, for example 172.16.5.4 255.255.240.0. The calculator converts the mask to its prefix length and fills in everything else.

Does it support IPv6?

No, this page handles IPv4 only, the dotted four-number addresses. ToolXkit has a separate IPv6 calculator for 128-bit addresses and their prefixes.

Why does it show an address class?

For reference only. Classes A, B and C were replaced by classless routing in 1993, but exams and older textbooks still mention them, so the class is shown with a note that it is historical.

Is Subnet Calculator accurate enough for real network work?

The maths behind addresses and ranges is exact, so the results match what a router expects. Double-check the input, especially the prefix length, since one wrong digit changes the whole range.

Do the calculators scan my network?

No. The subnet and speed calculators only work with the numbers you type in. They send no traffic into your network, and the only tool that connects anywhere is the WebSocket Tester, to the address you enter.

Why is my real download slower than the estimate?

The calculator assumes the full connection speed is available. In practice, WiFi, other devices, server limits and protocol overhead eat into it, so real downloads often take somewhat longer.

Is Subnet Calculator free and private?

Yes. It costs nothing and needs no account. What you type stays in your browser and is never sent to ToolXkit, which matters when it describes a real company network.

What is the difference between Mbps and MBps?

Mbps means megabits per second, the unit broadband plans use. MBps means megabytes per second, the unit most download windows show. One byte is eight bits, so 100 Mbps is about 12.5 MBps.

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