About Sumwise

Unit conversions, math calculators and printable worksheets.

Sumwise is a free toolbox for students, parents and teachers: unit conversions with worked steps, percentage and fraction calculators, times tables, printable math worksheets with answer keys, and spelling lists.

Every answer is calculated on the page from exact definitions, every worksheet is generated fresh with its answer key, and every step is shown so the method can be learned, not just the result copied.

Where the data comes from

Conversion factors from SI definitions (NIST SP 811). Calculations and worksheets are generated on this site; words from SCOWL (© Kevin Atkinson).

How pages are published

Every page is generated from the data above and has to pass a quality gate before it is offered to search engines. Pages with too few results stay reachable for visitors but are marked noindex and carry no advertising. Pages that only echo a visitor's own query, such as tool results, are never indexed.

Advertising

Sumwise is free to use and is paid for by display advertising. Ads are clearly separated from the content and never change what a page says. See the privacy policy for how ad partners use cookies.

Corrections

If you spot a mistake, write to [email protected]. Corrections are made in the underlying data, so every page that uses it is fixed at once.