Length is the conversion people need most, and it is also where rounding errors creep in. Since 1959 the international inch has been defined as exactly 2.54 centimetres, so one foot is exactly 0.3048 metres and one mile is exactly 1,609.344 metres. This converter uses those exact definitions rather than rounded approximations, so converting back and forth returns your original number. It covers metric units from millimetres to kilometres and imperial units from inches to miles, plus yards and nautical miles (exactly 1,852 m). Typical uses range from reading a US product spec sheet in centimetres to converting a 5K run into miles (3.107 mi) or checking whether a 6 ft 2 in sofa fits a 185 cm alcove.
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