Developer · Local utility

IPv4 Subnet / CIDR Calculator

Calculate IPv4 network, broadcast, usable hosts, masks, and CIDR details locally.

Runs locally · Nothing is uploaded

Local network workspace

IPv4 Subnet / CIDR Calculator

Calculate IPv4 subnet boundaries, host ranges, and masks without sending an address anywhere.

Enter an IPv4 subnet to start

Network, broadcast, usable hosts, masks, and address context will appear here.

Task path / input to outcome

How to calculate an IPv4 subnet or CIDR block

01
Enter an IPv4 address and prefix
Paste an address with CIDR, such as 192.168.1.42/24, or enter a plain IPv4 address and provide /0 through /32 or a contiguous dotted-decimal netmask in the second field.
02
Review the normalized subnet
As soon as the input is valid, the workspace shows the normalized CIDR, network address, broadcast behavior, first and last usable hosts, subnet mask, wildcard mask, and exact address counts.
03
Check edge-case semantics
A /31 is identified as an RFC 3021 point-to-point subnet with two usable endpoints and no broadcast address. A /32 is shown as one host route. Other prefixes use standard network and directed-broadcast boundaries.
04
Copy the values you need
Copy one result or the complete result set, then expand the binary and address-context panels when troubleshooting masks. Calculations and clipboard preparation stay in the current browser tab.

Your input stays in the browser.

IPv4 Subnet/CIDR Calculator uses its verified local execution path and does not create a hidden input or output history.

Local execution

Runs inside the current browser tab.

No hidden processing

Active tool data never becomes a Toolars document record.

No account required

Use the core workflow without creating a profile.

Immediate reset

Clear the tab and the active working data is gone.

Learn more about IPv4 Subnet/CIDR Calculator

When IPv4 Subnet/CIDR Calculator is useful

Focused transformations

Complete one well-defined browser task without setting up another application.

Copy-ready output

Review the result beside its source before copying or downloading it.

Fast validation

Catch malformed input and stale results before they enter another workflow.

What IPv4 Subnet/CIDR Calculator actually does

A network change request names 10.20.34.77/27, but the firewall rule needs the network boundary, wildcard mask, broadcast address, and usable host range. Paste the CIDR to get 10.20.34.64/27, verify the 30 usable hosts, and copy the exact fields into the change record without sending internal addressing data to a service.

Result stays explicit

The current result and selected settings stay visible before copy or download.

Built for review

Inspect relevant structure, metadata, or source context before using the result.

Private by default

No active workspace value is stored or sent to a server.

Errors stay explicit

Invalid values return a clear error instead of stale output.

Common questions

What inputs does the calculator accept?

It accepts one IPv4 address with an optional CIDR prefix, plus an optional separate prefix or contiguous dotted-decimal netmask. If both fields specify a prefix, they must agree. IPv6, CIDR merging, range-to-CIDR, and VLSM planning are outside this release.

Why does a /31 have no broadcast address?

RFC 3021 defines both addresses in a 31-bit prefix as usable endpoints on an IPv4 point-to-point link. The calculator therefore reports two usable hosts and marks broadcast as not applicable instead of applying the older network-and-broadcast subtraction rule.

Are the scope and class labels authoritative ownership data?

No. Scope comes from a static standards-based table for familiar special-purpose blocks, and the class label is historical context derived from the first octet. The tool performs no live IANA, RIR, ASN, routing, geolocation, or ownership lookup.

Are addresses uploaded or saved?

No. IPv4 parsing, mask arithmetic, binary rendering, copy preparation, and validation run locally. Raw addresses and results are not put into URLs, analytics, logs, remote requests, or browser storage; Reset or a reload clears the current input.

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