What this site is
StatGarden is a reference desk of calculators covering finance, health, maths, statistics, geometry, physics, unit conversion, dates and the home. Each tool does one job, shows the formula it evaluates, explains what every input means, and works through examples so you can check the result by hand or rebuild it in a spreadsheet.
The aim is narrow and practical: give the answer, then show the working. A number without its method is hard to trust and impossible to adapt, so every page prints the formula next to the tool rather than hiding it.
Nothing here goes out of date
Most calculators on the web quietly bake in a tax rate, an inflation figure, a fuel price or a contribution cap. The moment that figure changes, the tool is wrong, and there is usually no way for a visitor to tell. StatGarden takes the opposite approach: every rate, price, threshold and assumption is an input you set yourself.
The only fixed numbers in the code are ones that genuinely never change, such as pi, standard gravity, and defined unit conversion factors like the exact 28.349523125 grams in an ounce. Everything else is a field. That means these tools keep working the same way in five years as they do today, and it means you can run them against your own figures rather than someone else's assumptions.
How the worked examples are built
The example tables on every calculator page are not typed out by hand. When the site is built, each table declares a scenario and the real calculator is run to fill in the numbers. If a formula were ever changed, the tables would change with it on the next build.
This matters because hand-written examples are where errors live on most reference sites. Prose drifts away from the tool it describes, and nobody notices for years. Computing the examples from the same code that powers the calculator removes that whole category of mistake.
What StatGarden is not
These are calculators, not advice. The figures they produce are estimates for general guidance, and they are not financial, medical, legal or engineering advice. Health tools apply standard published formulas, but a formula cannot account for an individual's circumstances, and where a professional is the honest answer the pages say so.
Currency is shown with a generic dollar sign. The arithmetic is identical in any currency, so the tools work just as well in pounds, euros or anything else.
Getting in touch
Corrections are welcome, particularly on formulas. If a calculator disagrees with an authoritative source, that is worth knowing about, so please say which page and which figure. See the contact page for the address.