Best free subnet calculators
All three subnet calculators in this comparison are free with no account required, but they differ in scope: subnet-calculator.com is an IPv4-only, classful (Class A/B/C) calculator (subnet-calculator.com, read 2026-10-29), while calculator.net and AdminKit both handle IPv4 and IPv6 with CIDR notation; AdminKit's is the only one of the three whose own tool page states the math runs entirely in your browser with nothing sent to a server.
Three different scopes, named honestly
subnet-calculator.com, read 2026-10-29, is a classful IPv4 addressing calculator: its own page describes inputs and outputs entirely in terms of Class A, B and C addressing, with no mention of IPv6 anywhere on the page or on the related calculators it links to. It’s a free, no-signup tool with a copyright range (”© 2004 - 2026”) suggesting two decades of operation, but it is scoped to classful IPv4 math, not modern CIDR-only or IPv6 subnetting.
calculator.net’s IP Subnet Calculator, also read 2026-10-29, covers both IPv4 and IPv6, is free with no required sign-in, and is one of dozens of unrelated calculators (finance, fitness, math) the same site hosts. AdminKit’s subnet calculator is scoped narrowly to IPv4/IPv6 subnet math alongside AdminKit’s other free network tools, and its own tool page is explicit that every calculation happens in your browser’s JavaScript as you type, with nothing sent to a server — a claim this comparison could not verify one way or the other for the other two tools, since neither page states its computation architecture.
The honest angle
This isn’t a ranking. If you specifically need classful IPv4 terminology or have been using subnet-calculator.com for years, it still works for that scope. If you want a single calculator alongside a broad library of unrelated tools, calculator.net covers IPv4 and IPv6 in one wider site. AdminKit’s calculator is narrower in scope (just subnetting) but handles both IP versions, explains RFC 3021 point-to-point and single-host edge cases, and states plainly that it keeps your input in the browser.
For the underlying IP/network terms used here, see AdminKit’s IP lookup comparison.
Trademarks belong to their respective owners; AdminKit is not affiliated.
| Feature | AdminKit | subnet-calculator.com | calculator.net |
|---|---|---|---|
| Free, no account required | ✓ | ✓ | ✓ |
| IPv6 subnet calculations | ✓ | ✗ | ✓ |
| CIDR (classless) input and output, not just classful Class A/B/C | ✓ | ✗ | ✓ |
| Own tool page states calculations run entirely client-side, nothing sent to a server | ✓ | — | — |
| /31 (point-to-point) and /32 (single host) edge cases explained | ✓ | — | — |
AdminKit vs subnet-calculator.com
IPv6 subnet calculations
CIDR (classless) input and output, not just classful Class A/B/C
Own tool page states calculations run entirely client-side, nothing sent to a server
/31 (point-to-point) and /32 (single host) edge cases explained
AdminKit vs calculator.net
Own tool page states calculations run entirely client-side, nothing sent to a server
/31 (point-to-point) and /32 (single host) edge cases explained
Last checked
Sources: subnet-calculator.com — IP Subnet Calculator, calculator.net — IP Subnet Calculator
Frequently asked questions
Is AdminKit's subnet calculator better than subnet-calculator.com and calculator.net?
This page doesn't rank the three against each other. subnet-calculator.com is a long-running, IPv4-only classful calculator; calculator.net covers IPv4 and IPv6 alongside its wider suite of unrelated calculators; AdminKit's is IPv4 and IPv6, built into AdminKit's own set of free network tools, and states on its own tool page that it runs entirely client-side.
Does subnet-calculator.com support IPv6?
Not based on its own page: subnet-calculator.com's content exclusively describes classful IPv4 addressing (Class A, B and C) and makes no mention of IPv6 anywhere, including on the pages it links to for related IPv4 calculations.
Do subnet-calculator.com or calculator.net send my input to a server?
Unknown — neither page states its calculation architecture one way or the other, so this comparison marks that point as unverified rather than assuming either way. AdminKit's own subnet calculator page explicitly states the math runs entirely in your browser's JavaScript engine.
Does this page use subnet-calculator.com's or calculator.net's logo or brand assets?
No. Both names are used only to identify and compare publicly available tools (nominative use). AdminKit is not affiliated with or endorsed by either site.
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