CIDR / IPv4 Subnet Calculator
Host addresses normalize to their network. No probes or network lookups are performed. Enter one value in each field; whitespace, leading zeros, masks and IPv6 are not accepted.
Endpoint semantics, limits and privacy
/0 contains 4294967296 addresses. Conventional subnets exclude network and broadcast from usable hosts. /31 uses point-to-point semantics: both endpoints are usable. /32 is a single-host route with one usable address. For /31 and /32 the displayed broadcast is the arithmetic last address, not a directed broadcast.
Splitting requires a strictly longer prefix (digits only, no slash) and refuses more than 256 rows before enumeration. Each row shows its network/prefix and last address. No IPv6, dotted masks, network probing or geolocation.
Processing limits are 18 UTF-16 characters for CIDR and 2 for split prefix. Ordinary native edits clip before transport at 20 and 4 characters. Oversized edits are refused, never calculated from a clipped prefix. Refusal clears both inputs and stale report/Copy; shorten and re-enter, or Clear. These bounds do not certify hostile programmatic assignments or all IME behavior.
No payload persistence or logging is added. Interactive Auto server events traverse the Blazor connection; WebAssembly executes on-device. Copy explicitly places the report on your clipboard. Website active only; extension and Android discovery metadata is inactive, not hard route denial.
CIDR / IPv4 Subnet Calculator guide
Calculate IPv4 networks and bounded subnet splits.
Input and limitations
Strict dotted-decimal IPv4/CIDR, for example 192.168.1.42/24. Optional longer split prefix, at most 256 rows.
Check the selected options before using the result. Formatting and conversion do not establish that data is safe or suitable for your application.
How to use CIDR / IPv4 Subnet Calculator
- Enter an IPv4 address/prefix, optionally a longer split prefix, then Calculate.
- Copy the report with network, mask, broadcast, address and usable host counts.
- Clear removes both inputs, report and errors.
Example
Calculate 192.168.1.42/24 to obtain network 192.168.1.0/24, mask 255.255.255.0 and 254 usable hosts. Split prefix 26 produces four subnets. /31 uses both endpoints; /32 has one usable address.
Privacy on the website
The website uses Blazor Auto: interactive processing can run on the server or in your browser, depending on the current session. Do not assume pasted input stays on your device. Use non-sensitive sample data, and never place passwords, tokens or personal data in page URLs.
Search indexing covers public tool descriptions, not your input or generated output. See the privacy policy for website analytics and other data handling.
Install and offline help
Use your browser's install action, if available. Installation is optional; you can keep using this website normally.
Tools need an internet connection. Offline support provides a connection information page, not all-tools offline use.
Reset keeps favorites and preferences. It does not restore unsaved tool content.