Utilitoo
BlockSum Game - puzzle and math brain training

Subnet Calculator

Calculate subnet details and split networks.

Subnet planning is essential when designing office networks, cloud infrastructure, and container overlays. Utilitoo's Subnet Calculator accepts an IP address and prefix length, then returns network details including mask, broadcast, first and last host, and usable address count.

Optionally enter a larger prefix to split the network into smaller subnets - useful when dividing a /24 into multiple /26 segments for departmental VLANs or availability zones.

Select common prefix lengths from the dropdown or enter a custom mask. Results update with a clear breakdown and optional subnet split table. Pair with CIDR Calculator for notation-based input or DNS Lookup for hostname resolution.

All calculations run locally in your browser. Free and private for network engineers, sysadmins, and cloud architects.

Subnet Calculator is built for the inspect-edit-copy loop developers repeat dozens of times per day. Because Utilitoo runs in the browser, you avoid context switching to desktop utilities while reviewing logs, configs, or API responses. When output feeds into production systems, validate on a staging copy first.

Common use cases

  • Calculate subnet details and split networks - a common daily workflow on Utilitoo.
  • Preparing subnet calculator results to paste into pull requests, tickets, or team chat.
  • Validating subnet calculator data from a third-party API before wiring it into your application.
  • Teaching or documenting subnet calculator workflows without installing desktop software.
  • Cross-checking Subnet Calculator output against a colleague's result during pair debugging or code review.

Tips & common mistakes

Subnet Calculator runs entirely in your browser on Utilitoo, so you can paste sensitive API payloads, configs, or logs without uploading them. Start with a small sample to confirm the output format, then process the full input. If results look wrong, check for trailing commas, wrong encoding, or mixed line endings - common issues when copying from terminals or log viewers. Keep Subnet Calculator in a pinned tab during active development - it is faster than CLI one-offs for quick transforms. Use the Related Tools section to chain utilities without returning to the homepage.

Common errors

  • Unexpected output from Subnet Calculator - double-check input format, character encoding, and whether the source data was truncated when pasted.
  • Browser limits - very large inputs may slow or freeze the tab; split the data into smaller chunks if performance degrades.

How to use

  1. Enter IP and prefix.
  2. Optionally enter a new prefix to split.
  3. Click Calculate.

Frequently Asked Questions

How do I calculate a subnet from an IP?▼

Enter the IP and prefix (e.g. /24), click Calculate, and view network, mask, and host range details.

Can I split a subnet?▼

Yes. Enter a new larger prefix to divide the network into smaller subnets with a breakdown table.

IPv4 or IPv6?▼

This tool supports IPv4 subnet calculations.

What prefix lengths are common?▼

/24, /25, /26, and /27 are common for office and cloud subnets. /30 is typical for point-to-point links.

Is data sent to a server?▼

No. Subnet calculations run entirely in your browser.

Related Tools

CIDR Calculator

Calculate network details from CIDR notation.

IP Lookup

Look up IP address information.

DNS Lookup

Look up DNS records for any domain.

HTTP Header Viewer

View HTTP response headers for any URL.

User Agent Parser

Parse browser user agent strings.

Timestamp Converter

Convert Unix timestamps to dates and back.