Length Converter
Convert length between millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles using exact conversion factors.
Calculator Inputs
The length to convert. Zero and negative values are allowed.
The unit the value is currently in.
The unit to convert the value into.
- Converted Length
- 3.28
- Conversion
- meter to foot
About these results
CalcSpectrum calculators produce automated estimates using established formulas and the specific values you enter. Because real-world outcomes depend on input accuracy, mathematical assumptions, and rounding conventions, please verify critical figures with an appropriately qualified financial, tax, medical, legal, or other professional, as relevant.
How It's Calculated
Formula
Length conversion means expressing the same physical distance in a different unit. Every supported unit here converts through one canonical base unit, the meter: the input value is first multiplied by its unit's exact meters-per-unit factor to get the length in meters, then that meters value is divided by the target unit's meters-per-unit factor. Metric units (millimeter, centimeter, meter, kilometer) use exact powers of ten. US customary units use their internationally defined exact meter equivalents: 1 inch = 0.0254 m, 1 foot = 0.3048 m, 1 yard = 0.9144 m, 1 mile = 1609.344 m. Because every factor is exact, converting metric to US customary (or back) introduces no approximation beyond ordinary floating-point rounding.
Worked Examples
Metric to US customary: 5 kilometers to miles
- Convert to meters: 5 km x 1000 = 5000 m
- Convert meters to miles: 5000 m / 1609.344 m per mile = 3.106855961... mi
- Result: 5 km is approximately 3.106856 miles
US customary to metric: 1 foot to centimeters
- Convert to meters: 1 ft x 0.3048 = 0.3048 m
- Convert meters to centimeters: 0.3048 m / 0.01 m per cm = 30.48 cm
- Result: 1 foot is exactly 30.48 centimeters
Frequently Asked Questions
Why convert through meters instead of directly between units?
Converting every unit to and from one canonical base unit (the meter) means only one conversion factor per unit needs to be defined and verified, instead of a separate factor for every possible pair of units. This is the same approach international standards bodies use to define unit relationships.
Are the US customary conversion factors exact or approximated?
They are exact. The inch, foot, yard, and mile are all defined by international agreement as exact fractions of a meter (1 inch = 0.0254 m exactly, 1 foot = 0.3048 m exactly, 1 yard = 0.9144 m exactly, 1 mile = 1609.344 m exactly), so these conversions carry no approximation beyond standard floating-point precision.
Can I convert a negative length?
Yes. This calculator treats length as a generic numeric quantity and converts negative values the same way as positive ones — useful for representing a displacement or a difference between two measurements, not just a standalone distance.
What happens if I enter the same unit for both 'From' and 'To'?
The result equals the input value unchanged, since converting a unit to itself has a conversion factor of 1.