Inputs, methods, outputs
Tools describe the input units, assumptions and output. Examples show what to expect. Where a method has important limits, they appear below the tool rather than being hidden behind a claim of universal accuracy.
Calculation conventions
Mortgage calculations use fixed monthly payments. Compound interest assumes monthly compounding and deposits at month end. Calendar day differences use UTC to avoid daylight-saving shifts. The contrast checker uses relative luminance and the WCAG contrast formula.
What the tools can tell you
Results come from the values you enter and the method described on the page. A transfer-time estimate, for example, uses your chosen connection speed; it does not measure your internet connection. Random tools use your browser’s cryptographic random generator.
Testing and corrections
Calculation logic is checked against known examples and invalid inputs. Static pages are checked for metadata, internal links and sitemap entries. These checks do not certify medical, financial or legal suitability. If you spot a problem, send us the tool name and a small example through the contact page.
Funding
Tools are free. If advertising or affiliate recommendations are enabled, they must be distinguishable from tool controls. Sponsored links will be labelled. Advertising approval, income and search positions are not guaranteed.