- 1Choose file
- 2Adjust
- 3Download
Subnet & CIDR Calculator online, free
Calculate IPv4 CIDR subnet parameters: network address, broadcast address, netmask, wildcard mask, usable host range, and total capacity.
- Runs in your browser — no upload
- Free, no sign-up, no watermark
- TXT
How to use Subnet & CIDR Calculator · Subnet & CIDR Calculator — frequently asked questions
How to use Subnet & CIDR Calculator
- 1
Add your TXT file
Drop a file on the page, paste it, or click Select Files. Nothing is uploaded — it opens straight in your browser.
- 2
Fine-tune the settings
The defaults already suit most files; change them only if you need to.
- 3
Run Subnet & CIDR Calculator
Press the start button. Processing happens on your device, usually in seconds.
- 4
Download the result
Save the finished file, or continue with another tool without downloading in between.
What Subnet & CIDR Calculator can do
- Private by design — files are processed in your browser and never uploaded
- Free with no sign-up, no watermark and no daily limit
Subnet & CIDR Calculator — frequently asked questions
What is a CIDR subnet?
Classless Inter-Domain Routing (CIDR) is a method for allocating IP addresses and IP routing. It specifies the number of leading bits in the subnet mask (for example, `/24` represents `255.255.255.0`).
What parameters does the Subnet Calculator compute?
Given an IPv4 address and CIDR prefix length, the calculator determines the Network Address, Broadcast Address, Subnet Mask, Wildcard Mask, Usable Host IP Range (first to last), and Total Usable Hosts.
What is a wildcard mask?
A wildcard mask is the bitwise inversion of a subnet mask (where 0 indicates match and 1 indicates ignore), widely used in Cisco access control lists (ACLs) and OSPF routing configurations.
Which CIDR prefixes are supported?
The calculator supports all IPv4 CIDR prefix lengths from `/0` (the entire Internet) through `/32` (a single host), detailing special handling for `/30` and `/31` point-to-point links.
Is my network information kept private?
Yes. The subnet math executes 100% in your local web browser. No IP addresses or internal subnet structures are ever sent across the network.
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