About RACKCRUNCH
Free, plain calculators for people who build and run IT infrastructure.
What this site is
RACKCRUNCH is a set of free calculators for common infrastructure questions: RAID capacity and rebuild time, IPv4 and IPv6 subnetting, storage throughput, rack and UPS power, PoE budgets, CCTV and backup storage, VoIP trunk sizing, VM host density, ZFS RAIDZ capacity, data transfer time, electricity cost, Windows Server and SQL Server licensing, downtime cost, certificate expiry, and Linux chmod, cron and systemd helpers, plus end-of-life dates, security header checks, DNS lookups and SPF/DMARC checks.
Who runs it
RACKCRUNCH is built and maintained by the RACKCRUNCH team. We check each formula and rule against its primary source (vendor documentation, RFCs, standards bodies or the project's own source code) and link those sources on the tool pages and the Methodology page. Rules that change over time, such as licensing terms, certificate lifetimes and end-of-life dates, are reviewed regularly, and each tool page shows the date it was last reviewed. Questions and corrections go to hello@rackcrunch.com.
How the calculators are built
- Math first. Every result comes from a stated formula. The Methodology page lists the formula and the main assumptions for each calculator.
- Assumptions stay visible. Each page has a note that says what the result includes and what it leaves out.
- Bad input is rejected, not guessed at. Out-of-range or impossible values show a clear error instead of a misleading number.
- Calculations run on your device. We do not store your inputs. The SSL Certificate Expiry Checker, Security Header Check, DNS Lookup and SPF/DMARC Checker send the domain name you enter to our server so the server can read that site's public certificate, response headers or DNS records. Calculator pages also show Google ads; see the Privacy Policy for what Google receives. Share links only hold structured values such as numbers, IP addresses and hostnames, never free text you type, and ads never run on a page while its address holds calculator values.
- No accounts. There is nothing to sign up for.
What our checks can and cannot establish
We check calculator formulas, units, limits and representative inputs with automated tests. A correct formula does not make a result a measurement of your equipment: disk performance, backup chains, network overhead and licensing terms still need checks against the system or vendor you use.
Lifecycle data starts from a published source snapshot. We compare changes with vendor documentation, hold unsupported changes, and keep vendor-specific notes where support rules need explanation. A published date is not a guarantee that your particular contract includes support.
Our research pages explain their sample, collection method, definitions and limits. Where supporting files are released, those pages link to them. Research findings describe the stated sample and date, not every business or every system.
Report a problem through Contact with the page, your inputs, the result and what you expected. Do not send passwords, API keys or private customer information.
Limits
These are planning estimates, not vendor quotes or engineering sign-off. Real systems have overheads, firmware behavior, and licensing terms that change. Check important numbers against the vendor's documentation before you buy or build.
Corrections
If you find a wrong result, a broken page, or an outdated rule, please report it through the Contact page. Include the calculator, the inputs you used, and what you expected.