OnSumoTools

Length Converter — Convert mm, cm, m, km, in, ft, yd, mi

Enter a length value, pick your unit, and see all other units instantly with the formula shown.

Length is the most common physical measurement, yet unit systems vary by region and discipline. Metric uses base-10 steps — millimeters to centimeters to meters to kilometers — while the US customary system uses inches, feet, yards, and miles with less tidy ratios. This converter covers all eight units used in everyday life, engineering, and navigation. Enter any value, pick your starting unit, and every other unit updates instantly with the exact conversion formula.

How to use the length converter

  1. Enter the length value you want to convert.
  2. Select the unit you are converting from using the dropdown.
  3. The tool shows all other units at once with the formula for each.
  4. Click Copy next to any result to copy it to your clipboard.
  5. Share a specific conversion by copying the URL — it preserves your value and unit.

Worked examples

  • ft to m: person's height

    Enter 6 and select foot. Formula: 6 times 0.3048 equals 1.8288 m. A person who is 6 ft tall is exactly 182.88 cm — often rounded to 183 cm.

  • km to mi: marathon distance

    Enter 42.195 and select kilometer. Formula: 42.195 times 0.62137 equals 26.219 mi. The official marathon distance is 42.195 km, equivalent to 26 miles and 385 yards.

  • in to cm: screen size

    Enter 15.6 and select inch. Formula: 15.6 times 2.54 equals 39.624 cm. A 15.6-inch laptop screen has a diagonal of 39.6 cm.

  • m to yd: swimming pool

    Enter 50 and select meter. Formula: 50 times 1.0936 equals 54.680 yd. An Olympic swimming pool is 50 m, or about 54.7 yards.

Conversion factor reference

FromToFormula
mftmultiply by 3.2808
ftmmultiply by 0.3048
minmultiply by 39.370
inmmultiply by 0.025400
kmmimultiply by 0.62137
mikmmultiply by 1.6093
mydmultiply by 1.0936
ydmmultiply by 0.91440
ftinmultiply by 12
inftmultiply by 0.083333
ftydmultiply by 0.33333
ydftmultiply by 3
miftmultiply by 5280
kmmmultiply by 1000
cminmultiply by 0.39370
mminmultiply by 0.039370

Real-world length reference

Object / DistanceMetricImperial
Credit card width85.6 mm3.370 in
A4 paper (long side)297 mm11.69 in
Standard door height2 m6.562 ft
Basketball court length28 m91.86 ft
1 city block (approx)80 m87.49 yd
Eiffel Tower height330 m1082.7 ft
English Channel width (narrowest)33.3 km20.70 mi
Earth diameter12,742 km7917.5 mi

Frequently asked questions

  • How do you convert feet to meters?

    Multiply the length in feet by 0.3048 to get meters. For example, 6 ft times 0.3048 equals 1.8288 m. The conversion is exact: 1 foot is defined as exactly 0.3048 meters.

  • How do you convert inches to centimeters?

    Multiply the length in inches by 2.54 to get centimeters. For example, 12 in times 2.54 equals 30.48 cm. This is an exact definition: 1 inch equals exactly 2.54 centimeters.

  • How do you convert kilometers to miles?

    Multiply the length in kilometers by 0.62137 to get miles. For example, 10 km times 0.62137 equals 6.2137 mi. Alternatively, divide by 1.60934.

  • How many feet are in a mile?

    There are exactly 5,280 feet in one mile. This is a fixed definition in the US customary and imperial systems. In metric, 1 mile equals exactly 1,609.344 meters.

  • How do you convert meters to yards?

    Multiply the length in meters by 1.09361 to get yards. For example, 100 m times 1.09361 equals 109.361 yd. This derives from 1 yard equaling exactly 0.9144 meters.

  • How many centimeters are in an inch?

    There are exactly 2.54 centimeters in one inch. This is an internationally agreed exact definition. So 1 inch equals 2.54 cm, and 1 cm equals about 0.39370 inches.

  • How do you convert millimeters to inches?

    Divide the length in millimeters by 25.4 to get inches. For example, 100 mm divided by 25.4 equals 3.9370 in. This is exact: 1 inch = 25.4 mm by definition.

  • How accurate are these length conversions?

    Results are shown to at least 5 significant figures using exact conversion factors. All imperial factors derive from exact SI definitions: 1 inch = 0.0254 m, 1 foot = 0.3048 m, 1 yard = 0.9144 m, and 1 mile = 1,609.344 m.

  • What is the difference between yards and meters?

    One yard equals 0.9144 meters, so a meter is slightly longer than a yard (about 9.36% longer). A 100-yard American football field is about 91.44 meters.

Related tools

Metric and imperial, side by side

Most of the world uses meters. The US still uses feet and inches. If you shop online, follow a recipe for a project, read a plan or travel, you hit both sooner or later.

The converter handles eight units: millimeters, centimeters, meters, kilometers, inches, feet, yards and miles. Enter a value, pick the units and the result appears with the formula used, so you can check the logic.

Numbers worth remembering

One inch is exactly 2.54 centimeters. That's a fixed definition, not a rounded figure. Everything else follows from it. A foot is 12 inches, or 30.48 centimeters. A yard is 3 feet, or 0.9144 meters. A mile is 5,280 feet, or about 1.609 kilometers.

For quick mental math, a meter is a bit more than a yard, and a kilometer is a bit more than half a mile. Good enough for a rough guess when you're standing in a store.

  • Feet to meters: multiply by 0.3048
  • Inches to centimeters: multiply by 2.54
  • Kilometers to miles: multiply by 0.6214
  • Millimeters to inches: divide by 25.4

How accurate is it?

The conversion factors are exact for the units listed, so the math is correct. The only rounding is in how many digits the display shows. If you need precision for machining or engineering, keep extra decimals and round at the end.

Don't convert twice. Going from feet to meters to inches adds rounding at each step. Convert once, straight to the unit you need.

Where each unit shows up

Millimeters rule in engineering drawings and phone specs. Centimeters are for body measurements and small furniture. Meters and kilometers handle rooms, roads and races. In the US, inches describe screens and tools, feet describe height and rooms, and miles describe driving.

A marathon is 42.195 kilometers, or 26.2 miles. A 5K is about 3.1 miles. Runners switch between the two all the time, and a converter saves a lot of squinting at a watch.

Yards versus meters

They look alike but aren't the same. A yard is 0.9144 meters, so the meter is about 9 percent longer. On a football field of 100 yards, the difference is roughly 9 meters. That's a big gap if you're buying fabric or planning a run.

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