How to Find Your Network Address and Usable IP Ranges Using a Subnet Mask

What a subnet mask actually does

A subnet mask is a filter that tells your devices which part of an IP address identifies the network and which part identifies individual devices on that network. When you know your IP address and subnet mask together, you can figure out what other devices can talk to yours directly, and which ones need to go through a router instead. This matters for home networks because it helps you understand which devices are "local" to you and which are remote.

The subnet mask looks like an IP address — for example, 255.255.255.0 — but it works differently. Instead of identifying a device, it's a pattern that separates the network portion from the device portion. In a home network, the most common subnet mask is 255.255.255.0, which means the first three numbers of your IP address identify your network, and the last number identifies your device.

Key Takeaways

A subnet mask like 255.255.255.0 means your network is identified by the first three numbers of your IP address, and the last number identifies your device.
Your network address is found by replacing the device portion with zeros — so 192.168.1.50 with mask 255.255.255.0 gives you network 192.168.1.0.
The broadcast address is found by replacing the device portion with 255 — so 192.168.1.255 in the same example.
Usable device addresses fall between the network address and broadcast address, excluding both endpoints.
You can do this math by hand for common home masks, or use an online subnet calculator if you're working with less common masks.

Finding your network address by hand

Start with your IP address and your subnet mask. Let's say your IP is 192.168.1.50 and your mask is 255.255.255.0. The 255s in the mask tell you "keep this part of the IP address." The 0s tell you "this part changes for different devices."

To find your network address, replace every part of the IP that corresponds to a 0 in the mask with 0. In this example, the mask is 255.255.255.0, so you keep 192.168.1 and replace the last number with 0. Your network address is 192.168.1.0. Every device on your home network will have an address starting with 192.168.1.

This works the same way for other common home masks. If your mask is 255.255.0.0 (less common, but used in some setups), you keep only the first two numbers. An IP of 172.16.50.100 with that mask gives you a network address of 172.16.0.0.

Finding your broadcast address

The broadcast address is the last address in your network range. To find it, replace every part of the IP that corresponds to a 0 in the mask with 255 instead of 0. Using the same example — IP 192.168.1.50 with mask 255.255.255.0 — you replace the last number with 255. Your broadcast address is 192.168.1.255.

The broadcast address is not assigned to any device. It's a special address that means "send this message to everyone on this network." Your router uses it, and some network tools use it, but you won't see it assigned to a computer or phone.

Calculating usable device addresses

The usable addresses for actual devices fall between the network address and the broadcast address, but not including either one. With network address 192.168.1.0 and broadcast address 192.168.1.255, your usable range is 192.168.1.1 through 192.168.1.254. That's 254 possible addresses for devices.

In practice, your router takes one of these addresses (usually 192.168.1.1), and your DHCP server (the part of the router that hands out addresses automatically) uses some of them. The rest are available for your devices. On a home network with a 255.255.255.0 mask, you'll never run out of addresses — 254 is far more than most homes need.

If you're setting up a static IP address for a device (like a printer or security camera), pick an address in this usable range that your DHCP server won't hand out. Many routers let you set a DHCP range — for example, 192.168.1.100 to 192.168.1.200 — so you can safely use 192.168.1.50 or 192.168.1.75 for static devices without conflicts.

Understanding /24, /16, and other slash notation

You may see subnet masks written as a slash followed by a number, like 192.168.1.0/24. The number represents how many bits of the IP address belong to the network. In an IP address, there are 32 bits total. A /24 mask means 24 bits are the network, leaving 8 bits for devices — which is exactly what 255.255.255.0 does.

Common home networks use /24 (255.255.255.0), which gives you 254 usable addresses. Some networks use /16 (255.255.0.0), which gives you 65,534 usable addresses — far more than a home would need. You might also see /25 (255.255.255.128) in some setups, which splits a network in half and gives you 126 usable addresses per half.

If you see slash notation and want to convert it to a traditional mask, count the number: each group of 8 bits becomes 255, and any remaining bits are calculated. A /24 is 8+8+8 = three full groups, so 255.255.255.0. A /25 is 8+8+8+1, so 255.255.255.128. You don't need to memorize this — it's just another way of writing the same information.

When you need a subnet calculator

For home networks, you can do the math by hand with 255.255.255.0 or 255.255.0.0. But if you're working with an unusual mask like 255.255.255.192 or 255.255.252.0, or if you're dividing a network into smaller subnets, a subnet calculator saves time and mistakes. Free tools like ipcalc.net or subnettingpractice.com let you enter your IP and mask and when ready see your network address, broadcast address, and usable range.

These calculators are informational tools — they don't connect to your network or change anything. They're useful if you're troubleshooting why a device can't reach another device, or if you're planning a network setup before you build it. Paste in your IP and mask, and the calculator shows you exactly what range of addresses can talk to each other directly.

Why this matters for your home network security

Understanding your subnet tells you which devices are on your local network and which are not. Devices with addresses in your usable range can talk to each other directly without going through the internet. Devices outside that range must go through your router and internet connection.

This is relevant to security because local devices can sometimes bypass certain protections. If you know your network range, you can better understand what "local network access" means when you're setting permissions on a device — for example, allowing a printer to be found by devices on 192.168.1.0/24 but not from the internet. It also helps you spot an unfamiliar device: if you see an address like 192.168.1.200 on your network and you only have 5 devices, something unexpected is connected.

Frequently Asked Questions

What's the difference between network address and IP address?

Your IP address identifies your specific device on the network — for example, 192.168.1.50. The network address identifies the entire network — for example, 192.168.1.0. Your device has one IP address; the network has one network address that applies to all devices on it.

Can I change my subnet mask?

Yes, but you usually shouldn't on a home network. Your router sets the subnet mask, and it defaults to 255.255.255.0 for most home setups. Changing it can break device communication. If you're thinking about changing it, the reason usually means you need a different router configuration instead.

Why do some home networks use 255.255.0.0 instead of 255.255.255.0?

A 255.255.0.0 mask gives you many more usable addresses — over 65,000 instead of 254. Older networks or very large organizations use this. For a home, 255.255.255.0 is standard and provides plenty of addresses for all your devices.

If I know the subnet mask, can I figure out someone else's network?

Yes — the math works the same way. But knowing someone's network address doesn't let you access it. You still need to be on that network physically or connected to it, and you still need authentication. The subnet mask is public information; it's not a security credential.

What if my device shows a different subnet mask than my router?

This usually means the device is on a different network or connected differently — for example, a guest network, a VPN, or a wired connection with different settings than wireless. Check your router's settings to see what mask it's using for each network, and make sure the device is connecting to the one you intend.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.