David Savanyu

Who I am

I am a software engineer and the founder of Savi Tech Limited, a private limited company registered in Scotland, United Kingdom (company number SC810783), which operates Calcs.finance. I built this site because most calculator pages hide their assumptions; I wanted a place where the formula, the worked example, and the limitations sit next to the result.

I am not a financial adviser, accountant, mortgage broker, or tax professional, and nothing on this site is personalised financial advice. What I bring is engineering discipline: every calculator is a deterministic implementation of a documented formula, and every published worked example is reproduced by an automated test before it ships.

How I write and validate calculators

• Each calculator starts from a documented formula with named variables, published on the calculator page itself, next to a step-by-step derivation.
• Outputs are pinned by deterministic fixtures, edge-case tests, and rounding-policy tests; the formula version shown on each page identifies the fixture set that validated it.
• Rule-dependent topics (tax, retirement, lending disclosures) are only described with reference to official sources such as the IRS, CFPB, FCA, or HMRC, and the calculators stay generic where rules vary by jurisdiction.
• Every page states what the estimate ignores, because the missing variables are usually what changes a real-world outcome.

Contact and corrections

Found a wrong number, an unclear assumption, or a broken example? Tell me and I will fix it and add a regression test for it.

• Contact Calcs.finance
• How formulas are validated
• Editorial policy
• About Calcs.finance and Savi Tech Limited