Methodology

This page explains how PracticalBench tools are built and what to expect from them. Individual tools may document category-specific detail on their own page — this page covers the general approach across the whole site.

How the logic is implemented

Every tool's calculation logic is a deterministic, side-effect-free function: the same inputs always produce the same output, and nothing about the calculation depends on hidden state. Formulas are written as ordinary code, reviewed like any other code, not generated from an opaque black box.

How assumptions are surfaced

Every calculator page lists the assumptions built into its defaults and formula — for example, a waste-allowance percentage, or a typical coverage rate for a product. Where a default is editable, you can override it with your own figure; where it isn't, the page says so.

How tools are tested

Each tool's calculation is checked against a documented worked example — the exact output the underlying function actually produces for a stated set of inputs, not a hand-typed guess. Interactive behaviour (forward/reverse mode switching, unit conversion, live results) is separately tested by simulating real user interaction in a browser-like environment, not just by testing the maths in isolation.

How units and conversions work

Where a measurement has more than one commonly used unit (for example metres and feet), the tool lets you switch between them — the number you see updates to represent the same physical quantity, it doesn't just relabel the same digits.

How local browser processing is identified

All current PracticalBench calculators run entirely in your browser — nothing you type is sent anywhere. If a future tool ever needs to send data somewhere (for example, a file-processing tool), that page will say so explicitly and truthfully; we don't make a blanket "nothing is ever uploaded" claim across the whole site, because that wouldn't stay true forever (our contact form, for instance, does send your message to us).

How limitations are documented

Every tool page has a "Limitations" note describing what the calculation doesn't account for. Estimates are labelled as estimates, not authoritative figures.

How updates are handled

Each tool page shows a "Last reviewed" date. When a tool's assumptions, defaults or logic change, that date is updated.

Reporting a problem

Found an incorrect result or a bug? Use our contact form and choose "Incorrect result" or "Tool problem" as the topic.