X9M8 builds free calculators, converters and decision tools to go with its articles. There are 17 here, grouped by topic. Each one states its method, its limits and its sources on the page.
Science and engineering
Calculators and converters for electronics, physics, measurement and the night sky.
HX711 load cell calculatorHow much of the HX711’s input range a load cell uses, the step size and the noise in grams, plus a two-point calibration.
Ohm’s law and power calculatorSolves voltage, current, resistance and power from any two known values.
Resistor color code calculatorReads 4-, 5- and 6-band resistors, and works backward from a resistance to the colors.
Ideal gas law calculatorSolves PV = nRT for pressure, volume, amount of gas or temperature, with unit conversion.
Half-life and decay calculatorRemaining amount, elapsed time or half-life from the other values, plus decay constant and mean lifetime.
Temperature converterCelsius, Fahrenheit, Kelvin and Rankine, with reference points from absolute zero to boiling water.
Unit converterLength, mass, volume, area, speed, pressure, energy, time and data units using exact defined factors.
Moon phase and dark-sky plannerThe moon’s phase and a rating for each of the next 30 nights for faint-object viewing.
Law and policy
Orientation tools for legal questions that come with new technology. General information only, not legal advice.
Patent or trade secret helperSeven questions that point toward a patent or a trade secret under US federal law.
Neural data laws comparedThe Colorado, California, Montana and Connecticut neural data laws side by side, with the catch each carries for a consumer EEG headband.
Sustainability
Writing, code and web tools
Everyday utilities that run entirely in your browser. Nothing you type or choose is uploaded.
Word counter and reading timeWords, characters, sentences and paragraphs, with reading and speaking time.
JSON formatter and validatorChecks JSON, formats or minifies it, and reports the position of any error.
YAML to JSON converterConverts YAML to JSON or JSON to YAML, with clear errors and a stated list of what is supported.
QR code generatorMakes a QR code from any text or address, with PNG and SVG download.
Password generatorRandom passwords or passphrases made in the browser, with an entropy estimate and nothing stored.
Image compressor and converterShrinks images and converts between JPEG, PNG and WebP without uploading them.
Tools give general information only. See the editorial standards for how figures and sources are handled, and corrections to report a mistake.