Calculation methodology

How results are calculated

Inputs are processed in the browser using the formula stated on each tool page. Calculations retain JavaScript numeric precision during intermediate steps and round only the displayed result unless the page states another rule. Currency tools normally show two decimal places; percentage and health estimates may show additional precision when it helps interpretation.

Our test checklist

• Reproduce the published worked example by hand.
• Test zero, decimal, large, and boundary inputs.
• Reject impossible operations such as division by zero.
• Check that units and time periods remain consistent.
• Compare standard finance formulas with an independent calculation.

Assumptions and changing information

A calculator is only as current as its inputs. Tax rates, lender fees, health recommendations, and local rules can change. Tools that accept a rate let you enter the current value; their results remain estimates and do not replace advice from a qualified professional or current authority guidance.

Corrections

If you find an issue, send the page URL, exact inputs, displayed result, and expected result through our contact page. This lets us reproduce the issue before changing both the tool and its explanation.