Methodology

Start with the individual tool

Read the instructions, examples and limitations on the tool page. A result depends on the values, units and options you enter. Our practical guides provide worked examples for selected tools.

Calculations, units and rounding

Check the input unit labels before calculating. Convert measurements consistently and keep the original values when checking a result. A displayed value may be rounded; avoid treating the last displayed digit as a guarantee of precision.

Calculators model a specific situation. Material estimates, costs, dates and health estimates can differ from real-world outcomes when conditions or assumptions change. Allow for the limits described by the tool and verify important results independently.

Sources and reproducibility

Where a tool or guide cites a formula or reference, use that source to check its scope and assumptions. If a source or formula is missing, ask us through Report an Issue. Include the tool URL, input values, expected result and the reference you used so the calculation can be reproduced.

File and browser tools

Output quality depends on the input file, chosen settings and browser capabilities. Keep your original file, inspect the output and compare it with your intended use. Compression can reduce quality; format conversion can change metadata or compatibility.

See each tool’s processing information and our Privacy Policy for how inputs are handled. Read Medical Review for the review status of health and medical tools.