Subnet Calculator

How to use Subnet Calculator

1. Open Subnet Calculator — it runs entirely in your browser with no setup.
2. Paste or type your input into the text area, or upload a file where supported.
3. Set any options you need. The result appears in the output panel — there is no upload step and no waiting on a server.
4. Review the output instantly; large inputs are handled locally without lag.
5. Copy the result to your clipboard or download it. Your data never leaves the page.

Why use Subnet Calculator?

• 100% free with no limits, no sign-up and no watermarks.
• Private by design — your data are processed in your browser and never uploaded to a server.
• Fast and lightweight, with instant results even on a phone or a slow connection.
• Works everywhere — any modern browser on Windows, macOS, Linux, Android or iOS.
• Part of a full programming suite, so related subnet tasks are one click away.

What people use Subnet Calculator for

• Calculating subnet mask, network and broadcast addresses.
• Dividing an address range into smaller subnets.
• Checking whether two hosts are on the same subnet.

Subnet Calculator: limits and things worth knowing

• The mask separates network from host bits: 255.255.255.0 is /24. A host ANDed with the mask gives the network address.
• Two hosts communicate directly only if they compute the same network address. A mismatched mask on one machine is a classic cause of one-way connectivity.
• Subnetting borrows bits from the host portion, so each additional subnet bit halves the hosts per subnet and doubles the number of subnets.
• RFC 1918 private ranges are 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 — these are not routable on the public internet.

Sources

• RFC 1918 — Address Allocation for Private Internets

Is it private and secure?

Your privacy is built in. Subnet Calculator runs completely on your device, so whatever you enter stays in your browser and is never transmitted, logged or stored on any server.

Network activity: none. Nothing is sent and nothing is fetched. This tool makes no network request at all once the page has loaded — which is why it keeps working if your connection drops.

You do not have to take that on trust — our privacy proof page publishes the Content-Security-Policy that enforces it, lists every third party it permits, and shows how to verify the whole claim yourself.

Learn more

Why Browser-Based Tools Are Safer for Your Files — Most online converters upload your files to a server. Client-side tools don't. Here's why that difference matters for privacy.