Sumivo

Sumivo is a set of 48 calculators for practical sums. Thirteen cover electrical work, such as battery runtime, Ohm's law, voltage dividers, LED series resistors and PCB trace resistance. Six cover manufacturing, including OEE, takt time, scrap rate and cutting speed. Nineteen handle math, such as fractions, rounding, base conversion and Roman numerals, and there are smaller groups for time and date, health and fitness, and unit conversion. You type values and get a result, with no account and nothing to install.

The interesting part is the method page. The site says every published calculator shows a Verified runs table with at least three real executions of the shipped formula, the synthetic inputs used, the expected values and where those came from, and that the build fails if they don't match. Sources are kept as versioned records naming the document, publisher, date and jurisdiction, and the site states that a search result or a competing calculator doesn't count as a source. You can download the verified runs as JSON. For something like a battery runtime estimate, that means you can see the model's assumptions before trusting the number.

Hobbyists sizing a battery pack, technicians checking a resistor value and people working on a production line who need a quick OEE or takt figure will find something here, along with students doing fraction and base-conversion homework. The catalog is still small. Time and date has a single calculator, so it's better as a set of focused single-purpose tools than as a full engineering suite. The terms say results are estimates rather than engineering, electrical, financial, medical or other professional advice, and the site asks you to verify critical results and consult a qualified professional for safety-critical work.

The About page names Jack Shi, founder and CEO of NexaPioneer LLC in Boulder, Colorado, as the maintainer. The privacy page calls the site an MVP with no user accounts and says calculator inputs are processed in your browser and not sent to a server or stored. It loads Google Analytics 4 and Google Tag Manager, and published pages load Google AdSense. Ad storage and personalization default to denied everywhere, and analytics defaults to denied in the EEA, the UK and Switzerland. The page also says plainly that there's no consent banner yet.