Our Methodology

Calcumatix exists to give you calculators you can trust. This page explains exactly how we build, test, and maintain them so you know what stands behind every result.

How We Select Formulas

We use standard, widely recognized formulas for every calculator. Where a field has an established convention, such as the amortization formula for loans, the Mifflin-St Jeor equation for basal metabolic rate, or WHO categories for BMI, we adopt it and cite it on the calculator page. We prefer formulas that are simple to state, easy to verify, and broadly accepted over novel or proprietary ones.

How We Test Calculations

Every formula lives in its own module, separate from the user interface, and is covered by automated tests. Each formula has multiple test cases spanning normal values, edge cases, rounding behavior, and invalid inputs. A calculator is not published until its formula passes these tests. Keeping the math independent of the interface means we can verify correctness directly and re-run every check whenever we make a change.

How We Round Results

Calculations run at full numerical precision internally. We round only for display, and only at the final step, using a rounding method that avoids common floating-point artifacts. The number of decimal places shown is chosen to suit the quantity, for example currency to two decimals and BMI to one. Because rounding happens last, intermediate steps never accumulate rounding error.

How We Select Sources

When a calculator relies on an established standard or published equation, we link to an authoritative source, such as a health organization, a peer-reviewed paper, or an official reference. We link to primary sources wherever possible and only cite sources that genuinely inform the calculation. We do not add citations for decoration.

How Often We Review Calculators

Each calculator page shows a "last updated" date. We review calculators periodically and whenever a relevant standard changes, a source is updated, or a user reports an issue. Reviews confirm that the formula, example, and cited sources still match current best practice.

What Limitations Apply

Every calculator states its assumptions and limitations on its own page. Common limitations include simplifications (such as a fixed interest rate), inputs the tool does not account for (such as fees or taxes), and the fact that population- level formulas do not capture individual variation. Read these notes before relying on a result.