Quantity Converter

Quantity conversion expresses the same physical measurement in another unit. Ten meters and approximately 32.8084 feet describe the same length; only the unit and numerical scale differ. This calculator groups compatible units into length, mass, volume, and time so that a value is never accidentally converted between unrelated dimensions. Select a category first, then choose a source and destination unit from that category. Each conversion uses a common base unit. Length values pass through meters, mass values through grams, volume values through liters, and time values through seconds. The source value is multiplied by its base-unit factor and divided by the destination factor. Using one coherent factor table makes reverse conversions consistent and supports every pair within a category without separate formulas for each direction. The length group includes meters, kilometers, feet, and statute miles. Exact definitions are used where available: one foot is exactly 0.3048 meter and one international statute mile is exactly 1,609.344 meters. The mass group includes grams, kilograms, avoirdupois pounds, and ounces. One international avoirdupois pound is exactly 453.59237 grams, and one ounce is one sixteenth of that pound. The volume group includes liters, milliliters, US liquid gallons, and US customary cups. A US gallon equals 3.785411784 liters, and the cup used here equals 236.5882365 milliliters. These are not the same as imperial gallons or imperial cups, so recipes and specifications should identify the measurement system. Volume also differs from mass: converting liters to kilograms requires the substance density and is outside a pure unit conversion. Time conversions use 60 seconds per minute, 60 minutes per hour, and 24 hours per day. The day is treated as a fixed 86,400 seconds. Calendar months and years are omitted because their lengths vary. Results retain up to eight decimal places to make both small and large conversions useful, but displayed precision does not imply that the original measurement was equally precise. Round the final result according to the quality of the input and the needs of the task. This tool is useful for engineering estimates, schoolwork, recipes, travel planning, shipping, and everyday comparisons. For regulated trade, laboratory calibration, or safety-critical design, confirm that the unit convention and rounding rules match the controlling standard. Unit conversion preserves a quantity mathematically, but it cannot correct an uncertain measurement or an incorrectly identified unit.