All-in-One Unit Converter

Using the All-in-One Unit Converter

1. Pick a category at the top: Length, Weight, Temperature, Speed, Area or Volume. This is the full-catalog converter - every tab exposes more units than the "quick" sibling.
2. Pick the "From" unit. In Length you will find millimeter through mile plus nautical mile and astronomical unit. Weight adds grain, carat, troy ounce and long ton. Volume exposes both US and Imperial gallons, Imperial pint and cubic inch.
3. Type the value. Output refreshes on every keystroke via a Preact onInput handler.
4. Pick the "To" unit in the second dropdown.
5. Swap or Copy. The swap button reverses direction; Copy puts the result on your clipboard through the Clipboard API.

Full Catalog vs Quick Converter

This page is designed as a comprehensive single-URL reference. The sibling "quick" unit converter (/tools/unit-converter/) trims each category to the five or six units that 95% of users need; this page keeps the full list. Use this one when you need an astronomical unit, an Imperial fluid ounce or a long ton; use the quick one when you just want cm to inches without scrolling past cubits. The arithmetic core is identical - every unit is a factor relative to an SI base (meter, kilogram, kelvin, second), and conversion is value * factorFrom / factorTo in IEEE 754 double precision. Temperature is the exception: it uses affine formulas because 0 C is not 0 F. All computation is local; the only network traffic after page load is the Google Analytics pageview ping.

When to Reach For the Full Catalog

• Converting astronomical distances - AU, light-year, parsec - in a physics or astronomy context.
• Reading a UK-sourced document that uses Imperial gallon, Imperial pint or long ton.
• Translating jewelry weights (troy ounce, grain, carat) against cooking ounces.
• Surveying or cartography work that mixes acre, hectare, section and square kilometer.
• Historical documents with furlong, chain, rod, or barleycorn.
• Maritime work that wants nautical miles and knots alongside statute miles and mph.

Pitfalls

Three that bite here more than in the quick converter. First: name collisions. "Ton" means short ton (US), long ton (UK imperial) or metric ton (tonne) depending on context; this page exposes all three, so check which you selected before trusting the number. "Ounce" is avoirdupois (28.35 g) for groceries, troy (31.10 g) for precious metals, and fluid (29.57 mL) for volume - do not mix them. "Gallon" is US (3.785 L) or Imperial (4.546 L) and the same name means both. Second: affine temperature. A 1-degree interval in Celsius equals a 1.8-degree interval in Fahrenheit, but the reading offsets by 32. If you need interval math (specific heat, thermal conductivity), use a slope-only conversion, not this converter\'s affine reading conversion. Third: small display drift. Round trips through IEEE 754 can show 0.9999999999 instead of 1; the arithmetic is exact at the definition level, the decimal display is not.

Historical Notes - How Did We End Up With Two of Everything?

The United States gained independence before the UK standardized its Imperial system (1824), so US customary units froze around the older English Queen Anne gallons and Winchester bushels. When the UK adopted the Imperial gallon (10 lb of water at 62 F, 4.54609 L), the US kept the wine gallon (231 cubic inches, 3.785411784 L). The 1959 international yard and pound agreement aligned the US and UK inch, foot, yard, mile, pound and ounce to identical metric-based definitions - but left the gallon divergence alone. The metre itself has been redefined four times since 1793 (meridian fraction, platinum bar, krypton wavelength, speed-of-light since 1983), and the kilogram was redefined via the Planck constant in 2019 (SI Brochure, BIPM 9th edition). The mess of unit names hides a perfectly clean mathematical edifice underneath.

Alternatives

The GNU units command-line tool is the canonical reference and supports roughly 3500 units including unit algebra (3 feet * 27 inches in square meters). Wolfram Alpha handles natural-language unit queries and propagates units through formulas. Python\'s pint library is ideal when conversions are one step in a longer calculation - it catches unit mismatches as exceptions rather than silent numeric errors. Google\'s inline converter is fastest for a single lookup but limited in breadth. Choose this page when you want browser-only speed, no installation, and broader coverage than a typical quick converter.