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Length Unit Converter

Length is the unit family architects and engineers touch most: drawing dimensions, setting out on site, product data sheets and survey figures rarely arrive in the same system. These converters move between metric and imperial length without rounding surprises.

Units covered

Metric units run from the millimetre used on construction drawings up to the kilometre used for infrastructure alignments. Imperial units cover the inch and foot used in North American documentation, plus the yard and mile for site and route distances. Every factor is exact by definition: one inch is 25.4 mm, one foot is 0.3048 m.

  • Millimetremm
  • Centimetrecm
  • Metrem
  • Kilometrekm
  • Inchin
  • Footft
  • Yardyd
  • Milemi

Where it is used

  • Reading a European product datasheet in millimetres while drawing in feet and inches
  • Converting setting-out dimensions between a metric survey and an imperial model
  • Checking clear heights, door widths and stair going against code minimums written in the other system
  • Translating route or site distances between kilometres and miles for logistics

Length conversions (56)

Each conversion opens the live converter with that pair preselected, plus the exact factor, worked examples and answers to common questions.

Millimetres are the drawing unit, not metres

Most construction documentation in metric countries is dimensioned in whole millimetres, which avoids decimal points and misread separators. Keep model units in millimetres and convert only for reporting, so rounding never enters the geometry.

Imperial fractions and decimal feet

Imperial drawings mix fractional inches with decimal feet. Convert to a decimal value first, do the arithmetic, then round once at the end. Rounding each intermediate step is where cumulative setting-out errors come from.

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