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DIY Cost Tools

Length Converter

Conversion Calculator

Length Converter

Convert a length to millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles at the same time. Enter one value, choose its unit, and compare every result instantly.

Close-up measurement reference with numbers and markings
Photo by Michael Myers on Unsplash.

Convert length

Millimeters3,048 mm
Centimeters304.8 cm
Meters3.048 m
Kilometers0.003048 km
Inches120 in
Feet10 ft
Yards3.333333 yd
Miles0.001894 mi

Results show up to six decimal places. Very small or large values may be displayed with additional significant digits.

How the length converter works

The calculator first converts your value to meters, which acts as the common base unit. It then divides that meter value by the factor for each destination unit. Because every result comes from the same base value, you can compare metric and U.S. customary units without performing a separate calculation for each one.

Length conversion formulas

  • 1 inch = 25.4 millimeters exactly
  • 1 foot = 12 inches = 0.3048 meter exactly
  • 1 yard = 3 feet = 0.9144 meter exactly
  • 1 mile = 5,280 feet = 1,609.344 meters exactly
  • 1 meter = 100 centimeters = 1,000 millimeters
  • 1 kilometer = 1,000 meters

To convert 10 feet to meters, multiply 10 by 0.3048. The result is 3.048 meters. The same length is 120 inches, 3.333333 yards, 304.8 centimeters, or approximately 0.001894 mile.

Choosing the right unit

Millimeters are useful for small part dimensions and precise fabrication. Centimeters work well for household objects, while meters are common for rooms and construction distances in metric plans. Inches and feet are typical for U.S. building work. Yards often describe fabric or landscaping lengths, and miles or kilometers are better for travel-scale distances.

Accuracy and rounding

The calculator uses exact defined relationships for inches, feet, yards, miles, and SI units, then rounds only the displayed results. Your practical accuracy is limited by the original measurement. A tape reading recorded to the nearest 1/8 inch should not be treated as if its converted millimeter value were laboratory-precise.

Frequently asked questions

How do I convert feet to meters?

Multiply feet by 0.3048. For example, 20 feet multiplied by 0.3048 equals 6.096 meters.

How do I convert inches to millimeters?

Multiply inches by 25.4. This relationship is exact, so 4 inches equals exactly 101.6 millimeters.

Does converting a value make it more precise?

No. A conversion changes the unit, not the quality of the original measurement. Keep a sensible number of significant digits for your project.

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Sources and review

Unit relationships follow the SI references maintained by the National Institute of Standards and Technology. Calculator logic and examples were reviewed by the DIY Cost Tools editorial team on September 22, 2026.

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