Methodology

How a number gets onto CalculatorHub, and how it stays correct.

1. Sourcing

We use primary and authoritative sources appropriate to each subject: government publications and legislation for statutory rates and public data, recognised standards bodies for engineering and electrical work, peer-reviewed research for medical formulas, and established mathematical methods for pure mathematics. Statutory and public-data figures start with the responsible authority: a tax authority, central bank, statistics agency or local authority. For every figure we record its authority, the deep link to the publication that supports it, its effective date, and the date we confirmed it.

2. Storing

Figures are never typed into a page. Each lives once in a versioned data file that is the single source of truth, so every tool and guide that needs it reads the same value. Changing it in one place updates everywhere on the next build.

3. Updating

An automated process checks each source on its own schedule, daily for market data like exchange and interest rates, and around budget and tax-year dates for statutory figures. It compares the official value to what we store and either applies a trusted change or opens it for human review. Money figures are reviewed by a person before they publish.

4. Verifying

Each tool carries a worked example with known inputs and a known answer, run as an automated test. Formulae are derived from the official rule and checked across edge cases such as zero, boundaries and the top bracket. A figure does not publish if it breaks a tool's worked example.

5. Showing our work

Each figure-bearing page displays its sources and a last-verified date, and significant changes are recorded in a public change history, so anyone, human or machine, can see that the figure is maintained and where it came from.

6. Counting the calculators

We report two figures because they measure different things, and we keep them distinct to avoid overstating the catalogue. There are about 6,700 distinct calculators: unique tools such as a mortgage calculator or a standard-deviation calculator. Each is published in several languages, and the United States tax and finance tools are localized to every state and, where the data exists, every county. Counting each of those language and jurisdiction variants as its own page gives the larger page count of 45,965 shown in our headline statistics. The tool finder searches the roughly 6,700 English calculators; the per-language hubs and the US state and county pages make up the remainder. The page count reflects genuine localized content (different language, different jurisdiction figures), not duplicated pages.

Market-variable figures

Some numbers, like your personal mortgage rate or insurance premium, have no single government value. We never assert these. They are editable inputs with sensible defaults, and where an official average exists (for example a published average mortgage rate) we show it clearly labelled as an average, not as your rate.

CalculatorHub provides general information, not financial, tax, legal or investment advice.