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The 26 pages that link to Conversion of units, each with the reason it gives.
Map scaleRelated: Map and ground distances must use compatible units when calculating a scale ratio.
Mass concentrationRelated: Values can shift between grams per liter and kilograms per cubic meter.
HorsepowerRelated: Conversions make differently defined horsepower ratings comparable in watts.
Metric prefixRelated: Changing prefixes is a common unit conversion, such as metres to millimetres.
ReciprocalRelated: Conversion factors often use reciprocal units to cancel the original unit.
Kilogram-forceRelated: Converting kilogram-force to newtons requires multiplying by exactly 9.80665.
Kilometres per hourRelated: It converts km/h to units such as metres per second or miles per hour.
QuartRelated: Converting a quart requires knowing whether it is US liquid, US dry, or imperial.
Short tonRelated: Converting short tons correctly requires the exact pound-to-kilogram relationship.
Kilogram per cubic metreRelated: Conversions connect kg/m³ with g/cm³ and other density units.