CONVERSIONS

Convert between metric and imperial length units. Enter a value and pick the units.

Value

From

Converted

—

In the target unit.

Usage Tip

Handy anchors: 1 inch = 2.54 cm, 1 foot ≈ 0.305 m, 1 mile ≈ 1.61 km, 1 meter ≈ 3.28 ft.

THE MATH

Convert to a base unit, then to the target:
result = value × (from factor ÷ to factor)

Length units convert by fixed ratios. Metric scales in powers of ten; imperial uses inches, feet, yards, and miles.
One inch is defined as exactly 2.54 cm, the bridge between the two systems.

Convert through a common base unit (here, meters) to go between any two units.
Metric prefixes scale by ten: milli, centi, base, kilo.
For long distances tiny rounding barely matters; for machining, use full precision.

Practical Notes

Length units come from two systems. The metric system is based on the meter and works in powers of ten, while the imperial and US customary systems use inches, feet, yards, and miles. One inch is exactly 25.4 millimeters, which defines the relationship between the two systems, and one mile is exactly 1,609.344 meters.

Handy equivalents include 1 foot as 304.8 millimeters, 1 yard as 0.9144 meters, and 1 kilometer as about 0.6214 miles. Drawings and parts may mix inches and millimeters, so check the units on every dimension. When you convert a tolerance, keep the same number of significant figures, since rounding a precise dimension can push a part out of tolerance.

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