# Length Converter

Free online length converter. Convert between millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles instantly with exact precision.

## What this calculates

Instantly convert between metric and imperial length units. This free calculator supports millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles with precise conversion factors.

## Inputs

- **Value** — min 0
- **From** — options: Millimeters (mm), Centimeters (cm), Meters (m), Kilometers (km), Inches (in), Feet (ft), Yards (yd), Miles (mi)
- **To** — options: Millimeters (mm), Centimeters (cm), Meters (m), Kilometers (km), Inches (in), Feet (ft), Yards (yd), Miles (mi)

## Outputs

- **Result** — The converted length value.
- **Conversion** — formatted as text — Step-by-step conversion explanation.

## Details

Length conversion is one of the most common unit conversions needed in everyday life, science, and engineering. The metric system (mm, cm, m, km) is based on powers of 10, making conversions within the system simple. The imperial system (in, ft, yd, mi) uses different ratios between units.

Key Conversion Factors

- 1 inch = 25.4 mm (exact, by definition)

- 1 foot = 12 inches = 0.3048 m (exact)

- 1 yard = 3 feet = 0.9144 m (exact)

- 1 mile = 5,280 feet = 1,609.344 m (exact)

- 1 kilometer = 1,000 meters

All conversions in this calculator use the exact international definitions, ensuring maximum accuracy for engineering, scientific, and everyday calculations.

## Frequently Asked Questions

**Q: How many centimeters are in an inch?**

A: There are exactly 2.54 centimeters in one inch. This is the international standard definition established in 1959. To convert inches to centimeters, multiply by 2.54. To convert centimeters to inches, divide by 2.54.

**Q: How do I convert kilometers to miles?**

A: To convert kilometers to miles, divide by 1.609344. For example, 10 km = 10 / 1.609344 = 6.21371 miles. A quick approximation: multiply kilometers by 0.6214 for a close estimate.

**Q: What is the difference between metric and imperial length units?**

A: Metric units (mm, cm, m, km) are based on powers of 10, making arithmetic simple. Imperial units (in, ft, yd, mi) use varying ratios (12 inches per foot, 3 feet per yard, 5,280 feet per mile). Most of the world uses metric; the US, Liberia, and Myanmar still primarily use imperial.

**Q: Are the conversion factors in this calculator exact?**

A: Yes. All conversion factors used here are based on the exact international definitions. For example, 1 inch is defined as exactly 25.4 mm, and 1 yard is exactly 0.9144 meters. These are not approximations.

---

Source: https://vastcalc.com/calculators/conversion/length-converter
Category: Conversion
Last updated: 2026-04-21