Methodology & Data Sources

Reviewed: July 2026

Every calculator on CalcLoop runs entirely in your browser — nothing you type is sent to a server or stored, except for the small number of tools explicitly marked Live check below, which query a public resolver directly from your browser (never through CalcLoop's own servers). This page lists the standard, RFC, or vendor documentation each tool is based on.

Static formula tools

These compute results locally from a fixed, well-established formula or standard — no external data is fetched.

  • RAID Capacity Calculator — standard RAID parity math (RAID 0/1/5/6/10/50/60) and OpenZFS documentation for RAIDZ1/2/3.
  • Subnet Calculator — IPv4 addressing per RFC 791, /31 handling per RFC 3021.
  • SLA Uptime Calculator — the standard "nines" uptime/downtime convention used across hosting and cloud SLAs.
  • Bandwidth & Transfer Time Calculator — standard bit/byte conversion math; the efficiency factor is a general planning estimate, not a live link measurement.
  • DNS Propagation & TTL Calculator — DNS caching/TTL behavior per RFC 1035 and RFC 2181.
  • Backup Retention & 3-2-1 Calculator — the 3-2-1 backup rule as documented by CISA.
  • MikroTik Firewall Rule Generator — official MikroTik RouterOS Firewall documentation for RouterOS 6.x and 7.x.
  • Cron Expression Calculator — standard POSIX/Vixie cron syntax (crontab(5)).
  • SPF Record Generator — RFC 7208 (Sender Policy Framework).
  • DMARC Record Generator — RFC 7489 (DMARC).

Live check tools

These query a public resolver directly from your browser at the moment you use them — results reflect the current state of the internet, not a cached or static answer.

  • DNS Lookup Tool — queries Cloudflare's 1.1.1.1 DNS over HTTPS resolver directly.
  • SPF Record Checker — resolves the live SPF record and nested includes via Cloudflare DNS over HTTPS, evaluated against RFC 7208.
  • DMARC Record Checker — resolves the live DMARC record via Cloudflare DNS over HTTPS, evaluated against RFC 7489.
  • IP Blacklist / DNSBL Checker — queries Spamhaus, Barracuda, SpamCop, SORBS, UCEPROTECT, PSBL and Backscatterer zones directly via DNS over HTTPS.

Accuracy & limitations

These tools are built to match the relevant standard or vendor documentation as closely as possible, but none of them are a substitute for testing against your actual environment, hardware, or mail provider before making production changes. Where a calculator makes a simplifying assumption (for example, RAID 50/60 assuming equal sub-arrays, or a live checker not evaluating SPF macros), that's noted directly on the tool's own page.

Found an error, an outdated reference, or a standard we should update against? Let us know via the contact page.