CIDR Range Calculator
Convert IPv4 CIDR notation into subnet masks, broadcast addresses, host ranges, and binary output directly in your browser. No API request is required.
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What this calculator shows
Every result starts with the network boundary defined by the prefix length. From that boundary, the calculator derives the broadcast address, first and last usable IPs, subnet mask, wildcard mask, and host counts that matter for routing, ACLs, and network planning.
The binary view makes the bit boundary visible so you can see why a /24, /27, or /30 lands where it does. This is useful when you need to explain subnetting changes or verify a firewall rule before deploying it.
How CIDR notation works
CIDR stands for Classless Inter-Domain Routing. The slash number tells you how many leading bits belong to the network portion of the address, and the remaining bits are available for hosts.
A /24 usually means subnet mask 255.255.255.0 with 256 total addresses. A /16 expands the host space significantly, while a /27 narrows the subnet to 32 total addresses for smaller segments.
Common use cases
- Planning firewall rules and IP allowlists from CIDR blocks.
- Checking subnet boundaries before configuring routes or VLANs.
- Verifying whether a private range is scoped the way you expect.
- Troubleshooting host addressing errors after network changes.
Frequently asked questions
- What is CIDR notation?
- CIDR notation writes an IPv4 network as an address plus slash prefix, such as 192.168.1.0/24. The prefix tells you how many leading bits belong to the network portion.
- How do I calculate an IP range from CIDR?
- Enter the CIDR block and the calculator derives the network address, broadcast address, subnet mask, wildcard mask, and first and last usable IPs from the prefix length.
- What does /24 mean?
- A /24 means the first 24 bits identify the network and the remaining 8 bits identify hosts. In IPv4 that usually maps to subnet mask 255.255.255.0 and 256 total addresses.
- What is the difference between subnet mask and CIDR?
- CIDR is the slash-prefix form like /24, while the subnet mask is the dotted-decimal equivalent like 255.255.255.0. They describe the same network boundary in different formats.
- What is a broadcast address?
- The broadcast address is the last IPv4 address in the subnet. Traditional IPv4 networks reserve it for sending to all hosts on the subnet at once.
- How many usable IP addresses are in a /24?
- A /24 contains 256 total IPv4 addresses and 254 usable host addresses in traditional subnetting because the network and broadcast addresses are reserved.
- Does a /31 have usable hosts?
- Yes. This calculator follows RFC 3021 semantics, so a /31 has two usable point-to-point addresses and no separately reserved network or broadcast host addresses.
- Can I use this as a subnet calculator?
- Yes. This CIDR range calculator doubles as a focused IPv4 subnet calculator for quickly checking masks, ranges, host counts, and subnet boundaries.