Subnet Calculator

Subnet Calculator turns any IPv4 address and CIDR prefix into the full picture of a network in seconds — the subnet mask, wildcard mask, network and broadcast addresses, the first and last usable host, and the exact host counts. It works completely offline and nothing you enter ever leaves your phone.

HOW IT WORKS
Enter an IPv4 address as four octets and choose a prefix from /0 to /32 with the slider or the plus and minus steppers. The app does pure integer and bitwise math on the 32-bit address and shows every derived value instantly:

- Subnet mask and wildcard mask in dotted decimal
- Network address (the first address in the block) and broadcast address (the last)
- First and last usable host address
- Total addresses (2 to the number of host bits) and usable hosts (total minus 2)
- The classful IP class (A, B, C, D or E)

Special cases follow the standards: a /31 is treated as a point-to-point link with two usable addresses (RFC 3021), and a /32 describes a single host.

WHAT YOU CAN DO
- Subnet any address and prefix and read the result instantly
- Browse a quick reference table of the common prefixes from /24 to /30, with mask and usable hosts for each
- Learn the math behind prefixes, masks, network and broadcast addresses, and host counts with a plain-language guide

SPOT-CHECK
192.168.1.0/24 gives a mask of 255.255.255.0, 256 total addresses, 254 usable hosts, network 192.168.1.0, broadcast 192.168.1.255, first host 192.168.1.1 and last host 192.168.1.254.

BUILT FOR CLARITY
A clean, focused design puts the host count first, with the mask and address range in tidy tiles right beside it. Light and dark themes, a tiny download, no clutter and no account required.

AN EDUCATIONAL UTILITY
This app is a learning and reference tool for standard IPv4 / CIDR subnetting. Always confirm critical addressing against your own network design and equipment. It is provided for general information and education only.

PRIVACY
The app collects no personal data and works fully offline. Ads are served by Google AdMob, which may use an advertising identifier as described in Google's policies.

Download Subnet Calculator for fast, reliable IPv4 subnetting wherever you work — in the field, in the lab or in class.