Who runs this site
NumFoundry is written and maintained by Larry, based in Guangzhou, China. I build small, single-purpose tools in my spare time, and I keep every formula visible on the page so you can check the arithmetic yourself.
Contact: hello@numfoundry.com
Why the site exists
Most calculator pages online are written to be long rather than correct. They restate the same formula four different ways, bury the tool below two screens of text, and never mention the conditions under which the arithmetic stops being valid. That is a poor trade for the reader.
Each tool here is built the other way round: the calculator loads first, the formula is stated in plain text, and there is a section on where the answer misleads. If a page cannot explain its own limits, it is not published.
How the numbers are produced
Every calculation runs in your browser in plain JavaScript. Nothing you type is transmitted, stored or logged. The formulas are printed on each page so you can check them against a source you trust.
Where a figure depends on hardware or market behaviour — rebuild rates, drive throughput, tax rates — the assumption is stated next to the number rather than hidden inside it.
Corrections
If a formula, a reference table or a stated assumption is wrong, it gets fixed and the page notes the change. Send corrections to hello@numfoundry.com with the page name and what you believe the correct figure is. Arithmetic errors are treated as urgent; wording preferences are not.
What this site is not
Not a brokerage, not a tax preparer, not a storage vendor, not a machine shop. Nothing here is financial, tax, legal or engineering advice, and no page recommends a specific security, product or tool. The calculators convert numbers; the decision remains yours.