Skip to main content

IP Subnet Calculator — CIDR network, broadcast, host range, mask, subnetting

Type an IPv4 CIDR and get network, broadcast, host range, mask, wildcard, class and subnet splits — browser-only.

  • Runs locally
  • Category Developer & DevOps
  • Best for Formatting, validating, shrinking, or inspecting code-adjacent text.

Subnet summary

Network address192.168.1.0
Broadcast address192.168.1.255
First usable host192.168.1.1
Last usable host192.168.1.254
Usable hosts254
Total addresses256
Subnet mask255.255.255.0
Mask (binary)11111111.11111111.11111111.00000000
Wildcard mask0.0.0.255
CIDR notation192.168.1.0/24
IP classC
ScopePrivate (RFC1918 / reserved)

Subnet this block

Showing 4 of 4 subnets

SubnetUsable rangeHosts
192.168.1.0/26192.168.1.1 – 192.168.1.6262
192.168.1.64/26192.168.1.65 – 192.168.1.12662
192.168.1.128/26192.168.1.129 – 192.168.1.19062
192.168.1.192/26192.168.1.193 – 192.168.1.25462

All subnet math runs in your browser with 32-bit integer operations. Nothing is sent to a server.

What this tool does

Paste an IPv4 address with a CIDR prefix like 192.168.1.10/24, a dotted mask, or a bare address, and this calculator returns the network and broadcast addresses, the first and last usable host, the usable host count, the total address count, the subnet mask in dotted-decimal and binary, the Cisco wildcard mask, the class (A-E), and whether the block is private RFC1918 / reserved or public. It also subnets for you: split a parent by a target prefix, by hosts per child, or by subnet count, and read each child's range and host count. Every value has a copy button. The math is 32-bit integer bit operations, so /31 is an RFC 3021 point-to-point link and /32 a single host route — the edge cases hand calculations get wrong. Inputs encode into the URL so a share link reproduces the subnet.

Tool details

Input
Text + Numbers
The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output
Live result + Copy
The result area focuses on usable output, with copy, download, or preview actions when supported.
Privacy
Browser-side processing
The main tool logic does not call an external API, so inputs normally stay in the current tab.
Save / share
Shareable URL state
Key settings are encoded in the URL so another person can reopen the same setup.
Performance budget
Initial JS <= 12 KB
No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit
Developer & DevOps · Developer
Category and role tags drive related tools, internal links, and quick fit checks.

How to use

  1. 1. Input

    Paste or drop your content into the tool panel.

  2. 2. Process

    Click the button. All processing is local in your browser.

  3. 3. Copy / Download

    Copy the result or download to disk in one click.

How IP Subnet Calculator (CIDR) fits into your work

Use it in the small gaps between coding, reviewing, debugging, and shipping.

Developer jobs

  • Formatting, validating, shrinking, or inspecting code-adjacent text.
  • Preparing snippets for documentation, tickets, commits, or handoff.
  • Checking a small payload quickly without switching tools.

Developer checks

  • Run irreversible transforms like minify or obfuscate on a copy.
  • Keep secrets out of pasted snippets unless the tool explicitly stays local.
  • Use your normal tests or linter before shipping transformed code.

Good next steps

These links move the current task into a more complete workflow.

  1. 1 IPv4 Address Extractor Extract, dedupe, and export ipv4 addresses from pasted text or uploaded local files. Open
  2. 2 DNS Record Explainer DNS record explainer — all 18 common record types (A, AAAA, CNAME, MX, TXT, SRV, etc.) with syntax, examples, and gotchas. Open
  3. 3 IPv4 Address List Validator Validate and explain issues in ipv4 addresses from pasted text or uploaded local files. Open

Real-world use cases

  • Plan a VLAN address scheme

    Carve a /16 into per-VLAN /24s by setting the new prefix, then read each subnet's network, range, and host count straight from the table instead of hand-counting offsets.

  • Size a subnet for a fixed host count

    Switch to "hosts per subnet", type the device count, and the tool picks the smallest prefix that fits — 50 hosts becomes a /26 with 62 usable addresses.

  • Write a firewall or ACL rule

    Confirm the network and broadcast boundaries before writing a rule, and copy the wildcard mask for a Cisco ACL or OSPF network statement.

  • Verify a DHCP scope

    Check that a proposed DHCP pool sits inside the usable host range (.1 to .254 for a /24) and does not collide with the gateway or broadcast address.

  • Teach or learn subnetting

    Step through /30, /31, and /32 to see exactly why point-to-point links and host routes behave differently from a normal subnet, with the binary mask shown alongside.

Common pitfalls

  • Counting all addresses as usable. A /24 has 256 addresses but only 254 usable hosts — the network (.0) and broadcast (.255) are reserved. /31 and /32 are the only exceptions.

  • Confusing the subnet mask with the wildcard mask. They are bitwise inverses; a Cisco ACL that expects 0.0.0.255 will silently misbehave if you paste 255.255.255.0.

  • Assuming a longer prefix always means more subnets and more hosts. A longer prefix gives you more subnets but fewer hosts each — the host bits are what you are trading away.

Privacy

All subnet arithmetic runs as plain 32-bit integer bit operations inside your browser tab. No address, prefix, or split plan is sent to any server, and there is no logging of what you calculate. One caveat: the IP and split settings are encoded into the shareable URL query string, so if you paste a "share link" containing an internal address range into chat or email, the destination's access log will record it. For sensitive internal plans, copy individual values rather than sharing the URL.

FAQ

Tool combos

Folks in your role tend to reach for these alongside this tool.

Browse all tools for this role
Made by Toolora · 100% client-side · Updated 2026-07-02