Length Conversion
Metric and imperial distance units
Required Parameters
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Quick Answer
1 inch = 25.4 mm exactly. 1 foot = 0.3048 m. 1 mile = 1.609 km. Each conversion between metric and imperial length uses exact definitions established by international agreement in 1959.
Calculateur de Conversion de Longueur
Convertissez entre unites de longueur.
Design Notes
PCB design commonly uses mils (thousandths of an inch) for trace width and via diameter, while board dimensions may be in mm. The exact definition (1 inch = 25.4 mm) ensures zero conversion error between systems.
Common Mistakes
- 1
Confusing mils (thousandths of an inch) with millimeters — 1 mil = 0.0254 mm, not 1 mm.
- 2
Forgetting that yards and meters are close but NOT equal: 1 yard = 0.9144 m (about 9% shorter).
- 3
Using different precision than the measurement justifies — a ruler measurement to 1 mm does not justify 6 decimal places after conversion.
Knowledge Base
Combien de mm dans un pouce (inch) ?
Exactement 25,4 mm. Cette définition est internationale depuis 1959. Donc 1 mil = 0,0254 mm = 25,4 µm (unité courante en conception PCB).
Comment convertir des mils en millimètres ?
Divisez par 39,37. Ou multipliez par 0,0254. Exemples : 10 mil = 0,254 mm, 100 mil = 2,54 mm (pas standard DIP). En conception PCB, 1 mil = 1 thou = 0,0254 mm.