Methodology

Shared principles

• Calculations use the full precision of your device; rounding only happens on display.
• Figures that come from outside (thresholds, coefficients, yields, rates) are data kept apart from the code, with their source and the date they were checked.
• Every calculation engine is covered by automated tests, with examples checked by hand.
• The language you choose never changes a result, only how it is shown (decimal point or comma, default units).
• Every tool is also recomputed by a second program, written separately, on thousands of random cases (more than 90,000 in all). Unit factors there are typed again from the NIST definitions, not copied from the site. These checks run again before every site update.

Units and currencies

Conversions use the exact unit definitions published by NIST and the BIPM (for example 1 inch = 2.54 cm and 1 pound = 0.45359237 kg).

Currencies use the daily average rate published by the Bank of Canada. It is an indicative rate: banks and exchange offices apply their own rates and fees.

Dates and times

Dates are calculated in the Gregorian calendar, leap years included. Time zones come from the IANA database built into your browser, with daylight saving time applied for the date you choose.

Health

BMI follows the World Health Organization cut-offs for adults. Resting energy uses the Mifflin-St Jeor equation (1990) and calorie needs the activity levels of the 2001 FAO/WHO/UNU report.

These results are estimates for healthy adults. They don't replace a health professional's advice and don't apply during pregnancy or breastfeeding, or to children.

Cooking

Bread dough uses baker's percentages, with the levain counted in the total flour and water. Cup-to-gram conversions use the weights published by the US Department of Agriculture (USDA, FoodData Central); they are averages, and a scale stays more precise.

Home and materials

Areas and volumes are simple geometry. Yields per bag or per can come from the data sheets of the manufacturers cited (QUIKRETE, Sherwin-Williams) and can be replaced by those of your own product. The waste margin is your choice.

These tools estimate material quantities; they don't replace a structural calculation or the building codes in force.

What is not taken into account

• No tool gives personal advice.
• Taxes, fees and product prices are not included unless you enter them.
• Health formulas don't account for body composition, illness or treatment.
• Material calculators don't plan cuts, formwork or reinforcement.

How we build, check and fix the tools

• Each tool answers a question people really ask, with one page per need.
• Every outside figure (cut-off, coefficient, yield, rate) is read on its official source or the manufacturer's data sheet, then cited with its date. With no readable source, the tool waits: body fat and water needs are on hold for that reason.
• Figures in the texts are never typed by hand: they come from the same data and calculations as the tool, so a text cannot contradict it.
• Every calculation is tested against reference values, then recomputed by an independent program before each site update.
• No tool is paid for by a brand, and a result never depends on the language you choose.
• When an error is reported, we fix its cause in every tool concerned, add a test so it cannot come back, and update the date shown.

Report a mistake

If a result looks wrong, write to our address (the “Write to us” button below) with the tool and the values you used. We check every report and fix the cause in every tool it affects.