Subnet Calculator: Calculate IP Subnets & CIDR | Free Tool

A A subnet mask separates the network portion from the host portion of an IP address. /24 = 255.255.255.0.

A Yes.

A Our IP Subnet Calculator simplifies finding the usable host IP range. Simply enter your network's IP address and the CIDR prefix (e.g., 192.168.1.0/24) into the tool. It will instantly display the 'Usable IP Range,' showing the first and last IP addresses available for assigning to devices. This excludes the network address and the broadcast address, crucial for efficient network planning and avoiding configuration errors.

A Our IP Subnet Calculator makes this simple. Enter your network's IP address and the CIDR prefix (e.g., 192.168.1.0/27). The tool instantly displays the 'Host Count,' which represents the total number of IP addresses in that subnet. To find the *usable* IP addresses, subtract two (for the network and broadcast addresses) from this total, giving you the assignable range for your devices.

A The network address identifies the specific subnet itself, and you can't assign it to a device. Similarly, the broadcast address is used to send data to all devices within that subnet, so it's also reserved. Our calculator shows these clearly, for example, with a /24 network like 192.168.1.0/24, the network address is 192.168.1.0 and the broadcast is 192.168.1.255.

A No, this tool only handles IPv4 addresses. IPv6 uses a completely different addressing scheme with 128-bit addresses. For IPv6, you'd need a dedicated IPv6 subnet calculator. A common workaround is to use command-line tools like `ipcalc` or online tools specifically built for IPv6. If you're managing mixed environments, keep both tools bookmarked.

A Two addresses are always reserved: the network ID and the broadcast address. For a /30 subnet, that gives you only 2 usable hosts out of 4 total IPs. Many people forget to subtract these two when planning. If you're configuring a point-to-point link, a /30 is perfect. But for a small office network, a /24 gives you 254 usable addresses. Always check the 'Usable IP Range' field in our calculator before assigning anything.

A Not exactly — it depends on whether the network uses RFC 3021 or not. Standard subnets reserve the network ID and broadcast address, so a /24 gives 254 usable IPs out of 256 total. But for point-to-point links, RFC 3021 allows using a /31 with zero waste, giving you 2 usable addresses. Most home and office networks stick with the /24 standard. Always check the 'Usable IP Range' in our calculator before deploying.

A Yes, those are completely different subnets. A router can handle multiple subnets as long as each interface or VLAN has its own unique network address. What you cannot do is overlap them — like using 192.168.1.0/24 and 192.168.1.0/25 on the same router. That would create routing confusion. Our calculator helps you visualize exactly where one subnet ends and another begins. Typing both ranges in quickly shows they don't share any IPs.

A Yes, every time you adjust the /prefix, the subnet mask updates instantly. A /24 gives 255.255.255.0, but a /25 shifts that to 255.255.255.128. The tool recalculates the network address, broadcast, and usable range on the fly. Try dragging the slider from /24 to /28 and watch the usable hosts drop from 254 to 14. That's a quick way to see how subnet boundaries tighten.