Trust and methodology
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UnitConversion.free is an ad-supported, browser-only unit converter covering 17 measurement dimensions. This page documents who operates the site, how conversion logic works, what coverage exists, and what users should know before relying on a result for safety-critical or regulated work.
UnitConversion.free is built and maintained by Kevin Kinnett, a senior software engineer with close to two decades of experience in .NET, Azure, Kubernetes, and cloud-native architecture. Kevin also writes about software engineering, emerging technology, and adjacent topics at kevinkinnett.com.
The site is operated as a single-author project rather than a content farm or marketplace. Calculator logic, prerendered SEO content, schema markup, and editorial methodology are all authored and reviewed by Kevin. The same applies to the trust pages: privacy, terms, contact, and this about page.
Every conversion on the site flows through a single typed unit catalog plus a small conversion engine. Each unit is registered with its base factor relative to the SI coherent unit for its dimension (meter for length, kilogram for mass, kelvin for temperature, second for time, and so on). Converting any input value from unit A to unit B is then a single multiplication: input × (factor_A / factor_B). There is no static lookup table; the same engine handles all 17 dimensions.
For conversions defined exactly by international agreement (1 ft = 0.3048 m, 1 inch = 25.4 mm, 1 lb = 0.45359237 kg, 1 mile = 1.609344 km, 1 BTU IT = 1,055.05585262 J), the base factors are stored to full definitional precision. For derived units (square meters to acres, joules to kilowatt-hours, density across systems), the factors compose from those exact primitives. Accuracy is bounded by the precision of the registered constants and by JavaScript double-precision arithmetic (IEEE 754 binary64, about 15-17 significant decimal digits).
The site covers 17 measurement dimensions: length, mass, temperature, volume, speed, area, time, pressure, energy, power, frequency, angle, digital storage, data rate, force, fuel economy, and density. Within each dimension, the most common units (metric base unit, US/imperial equivalents, common technical units) are surfaced first. Less common units are present in the catalog and reachable through the live converter on each dimension page.
Sixteen pair-specific calculator routes exist for popular conversions that users search for directly: meters to feet, Celsius to Fahrenheit, kg to lbs, km to miles, liters to gallons, cups to mL, mph to km/h, Mbps to Kbps, MPG to L/100km, and others. Each pair page has a citation-friendly lead answer, formula explanation, a 10-row common-values table, and a 5-entry FAQ block.
The site is updated when authoritative definitions change (the 2019 SI redefinition, the 2023 NIST retirement of the US survey foot), when a new commonly-searched conversion warrants its own pair page, or when content needs corrections. Site-wide last-update dates are tracked in the sitemap. Individual page updates are reflected in the dimension or pair page content.
For everyday use (cooking, room measurements, route distances, fitness logs), the conversions on this site are accurate to far more precision than the use case requires. For safety-critical, legal, or regulated work, cross-reference the final value against your governing standard rather than relying on the calculator alone.
The primary international references this site relies on:
Every conversion runs entirely in your browser. Conversion inputs, results, and history are never sent to a server. The site does use Google Analytics 4 to understand which dimensions and unit pairs are visited (no per-user profile is built), and it stores your theme preference (light, dark, or system) in your browser's local storage so that choice persists across reloads. Full detail is on the privacy policy page.
UnitConversion.free uses a typed unit catalog and conversion engine for every result rather than a static lookup table. Conversions are computed from the defined base factors in the catalog, so accuracy is bounded by the precision of those constants and by JavaScript double-precision arithmetic. For safety-critical, legal, or regulated work, verify the final value against your governing standard.
17 dimensions are covered: length, mass, temperature, volume, speed, area, time, pressure, energy, power, frequency, angle, digital storage, data rate, force, fuel economy, and density. Each dimension has its own route with the most common unit pairs surfaced first, plus dedicated pair-specific calculator pages for popular conversions like meters to feet, Celsius to Fahrenheit, and MPG to L/100km.
No. All conversions run entirely in your browser. The site stores only your theme preference in local storage so the light, dark, or system mode choice persists across reloads. No conversion inputs, results, or usage history are sent to a server.
Cite the source unit, the target unit, the numeric result, and the page you used (for example: "Meters to Feet Converter at https://unitconversion.free/meters-to-feet"). For academic or engineering work, cross-reference the result with an authoritative standard such as NIST SP 811 (US) or BIPM's SI brochure (international) so the primary reference is the standard, not the calculator.
Yes. The header includes explicit Light, Dark, and System choices, and your selection persists across reloads.
Yes. The desktop side rail collapses into a horizontal category strip, and the main cards scale down for smaller screens without changing the route structure.