The Complete Guide to Length Conversions

Consider this the master page for length conversions. Below you'll find every supported unit explained, the precise factors connecting them, and computed tables you can rely on for homework, work or travel.

Prefer a calculator? Every conversion on this page has an instant, free tool — start at the tools hub or use the links under each unit below.

The units at a glance

Millimeter (mm)

The millimeter is one thousandth of a meter and the workhorse of precision measurement — engineering drawings, 3D printing tolerances and rainfall totals are all quoted in millimeters.

• 1 mm = 0.1 centimeters (cm) — Millimeter to Centimeter converter
• 1 mm = 0.001 meters (m) — Millimeter to Meter converter
• 1 mm = 0.000001 kilometers (km) — Millimeter to Kilometer converter
• 1 mm = 0.03937 inches (in) — Millimeter to Inch converter
• 1 mm = 0.003281 feet (ft) — Millimeter to Foot converter
• 1 mm = 0.001094 yards (yd) — Millimeter to Yard converter

Centimeter (cm)

The centimeter, one hundredth of a meter, is the everyday small unit of the metric world: body height, clothing measurements and school rulers all speak in centimeters.

• 1 cm = 10 millimeters (mm) — Centimeter to Millimeter converter
• 1 cm = 0.01 meters (m) — Centimeter to Meter converter
• 1 cm = 0.00001 kilometers (km) — Centimeter to Kilometer converter
• 1 cm = 0.393701 inches (in) — Centimeter to Inch converter
• 1 cm = 0.032808 feet (ft) — Centimeter to Foot converter
• 1 cm = 0.010936 yards (yd) — Centimeter to Yard converter

Meter (m)

The meter is the SI base unit of length, defined by the distance light travels in a vacuum in 1/299,792,458 of a second. Nearly every other length unit is now legally defined against it.

• 1 m = 1,000 millimeters (mm) — Meter to Millimeter converter
• 1 m = 100 centimeters (cm) — Meter to Centimeter converter
• 1 m = 0.001 kilometers (km) — Meter to Kilometer converter
• 1 m = 39.3701 inches (in) — Meter to Inch converter
• 1 m = 3.2808 feet (ft) — Meter to Foot converter
• 1 m = 1.0936 yards (yd) — Meter to Yard converter

Kilometer (km)

The kilometer (1,000 meters) is the standard unit for road distances and running races nearly everywhere outside the United States and the United Kingdom.

• 1 km = 1,000,000 millimeters (mm) — Kilometer to Millimeter converter
• 1 km = 100,000 centimeters (cm) — Kilometer to Centimeter converter
• 1 km = 1,000 meters (m) — Kilometer to Meter converter
• 1 km = 39,370.08 inches (in) — Kilometer to Inch converter
• 1 km = 3,280.84 feet (ft) — Kilometer to Foot converter
• 1 km = 1,093.61 yards (yd) — Kilometer to Yard converter

Inch (in)

The inch has been defined as exactly 2.54 centimeters since 1959. Screen sizes worldwide are still quoted in inches, making it one of the most-converted units on the internet.

• 1 in = 25.4 millimeters (mm) — Inch to Millimeter converter
• 1 in = 2.54 centimeters (cm) — Inch to Centimeter converter
• 1 in = 0.0254 meters (m) — Inch to Meter converter
• 1 in = 0.0000254 kilometers (km) — Inch to Kilometer converter
• 1 in = 0.083333 feet (ft) — Inch to Foot converter
• 1 in = 0.027778 yards (yd) — Inch to Yard converter

Foot (ft)

The foot (12 inches, exactly 0.3048 meters) remains the standard unit for human height and aviation altitude — even airlines in fully metric countries fly at "35,000 feet".

• 1 ft = 304.8 millimeters (mm) — Foot to Millimeter converter
• 1 ft = 30.48 centimeters (cm) — Foot to Centimeter converter
• 1 ft = 0.3048 meters (m) — Foot to Meter converter
• 1 ft = 0.0003048 kilometers (km) — Foot to Kilometer converter
• 1 ft = 12 inches (in) — Foot to Inch converter
• 1 ft = 0.333333 yards (yd) — Foot to Yard converter

Yard (yd)

The yard (3 feet, exactly 0.9144 meters) survives mainly on sports fields — American football is measured in yards — and in fabric and landscaping trades.

• 1 yd = 914.4 millimeters (mm) — Yard to Millimeter converter
• 1 yd = 91.44 centimeters (cm) — Yard to Centimeter converter
• 1 yd = 0.9144 meters (m) — Yard to Meter converter
• 1 yd = 0.0009144 kilometers (km) — Yard to Kilometer converter
• 1 yd = 36 inches (in) — Yard to Inch converter
• 1 yd = 3 feet (ft) — Yard to Foot converter

Mile (mi)

The statute mile is exactly 1,609.344 meters. It descends from the Roman mille passus — a thousand paces — and still rules road signs in the US and UK.

• 1 mi = 1,609,344 millimeters (mm) — Mile to Millimeter converter
• 1 mi = 160,934.4 centimeters (cm) — Mile to Centimeter converter
• 1 mi = 1,609.34 meters (m) — Mile to Meter converter
• 1 mi = 1.6093 kilometers (km) — Mile to Kilometer converter
• 1 mi = 63,360 inches (in) — Mile to Inch converter
• 1 mi = 5,280 feet (ft) — Mile to Foot converter

Every conversion formula

The table below lists the exact formula for every length pair we support. All factors derive from the SI definitions of the units, so chaining them never introduces error.

One-line cross reference: every unit in every other unit

The complete pairwise reference — every supported length unit expressed in each of the others:

• 1 millimeter = 0.1 centimeters
• 1 millimeter = 0.001 meters
• 1 millimeter = 0.000001 kilometers
• 1 millimeter = 0.03937 inches
• 1 millimeter = 0.003281 feet
• 1 millimeter = 0.001094 yards
• 1 millimeter = 0.00000062 miles
• 1 centimeter = 10 millimeters
• 1 centimeter = 0.01 meters
• 1 centimeter = 0.00001 kilometers
• 1 centimeter = 0.393701 inches
• 1 centimeter = 0.032808 feet
• 1 centimeter = 0.010936 yards
• 1 centimeter = 0.00000621 miles
• 1 meter = 1,000 millimeters
• 1 meter = 100 centimeters
• 1 meter = 0.001 kilometers
• 1 meter = 39.3701 inches
• 1 meter = 3.2808 feet
• 1 meter = 1.0936 yards
• 1 meter = 0.00062137 miles
• 1 kilometer = 1,000,000 millimeters
• 1 kilometer = 100,000 centimeters
• 1 kilometer = 1,000 meters
• 1 kilometer = 39,370.08 inches
• 1 kilometer = 3,280.84 feet
• 1 kilometer = 1,093.61 yards
• 1 kilometer = 0.621371 miles
• 1 inch = 25.4 millimeters
• 1 inch = 2.54 centimeters
• 1 inch = 0.0254 meters
• 1 inch = 0.0000254 kilometers
• 1 inch = 0.083333 feet
• 1 inch = 0.027778 yards
• 1 inch = 0.00001578 miles
• 1 foot = 304.8 millimeters
• 1 foot = 30.48 centimeters
• 1 foot = 0.3048 meters
• 1 foot = 0.0003048 kilometers
• 1 foot = 12 inches
• 1 foot = 0.333333 yards
• 1 foot = 0.00018939 miles
• 1 yard = 914.4 millimeters
• 1 yard = 91.44 centimeters
• 1 yard = 0.9144 meters
• 1 yard = 0.0009144 kilometers
• 1 yard = 36 inches
• 1 yard = 3 feet
• 1 yard = 0.00056818 miles
• 1 mile = 1,609,344 millimeters
• 1 mile = 160,934.4 centimeters
• 1 mile = 1,609.34 meters
• 1 mile = 1.6093 kilometers
• 1 mile = 63,360 inches
• 1 mile = 5,280 feet
• 1 mile = 1,760 yards

Real-world reference points

For intuition: a credit card is 85.6 mm wide, a doorway about 2 meters tall, a city block roughly 100 meters, a 5K fun run is 3.1 miles, and a marathon is 42.195 km (26.219 miles). Anchoring conversions to objects you know makes estimates far more reliable than raw arithmetic.

Most-used conversion tables

Kilometer to Mile

Mile to Kilometer

Foot to Mile

Millimeter to Inch

Centimeter to Foot

Millimeter to Centimeter

Centimeter to Millimeter

Centimeter to Meter

Common mistakes to avoid

The most common length-conversion mistakes are mixing up feet and meters when reading foreign real-estate listings, forgetting that a mile is much longer than a kilometer (runners painfully rediscover this), and rounding 2.54 cm/inch to 2.5 — a 1.6% error that compounds badly over long distances.

Tips for accurate conversions

• Round once, at the end. Chaining conversions and rounding each step compounds error surprisingly fast.
• Watch for regional unit variants. Some unit names have US and imperial variants with different sizes — always check which one your source means.
• Estimate first, then compute. A rough mental figure catches order-of-magnitude mistakes before they end up in your work.
• Use exact factors for anything official. The factors in this guide are the internationally defined values, not approximations.

Frequently asked questions

Which length unit should I use?

Use the unit your audience expects: metric units for international and scientific audiences, US customary units for American everyday contexts. When in doubt, give both — "5 km (3.1 mi)" style.

Are these conversion factors exact?

Yes. Every factor on this page comes from the internationally agreed definition of the units involved (most were fixed by treaty in 1959 or by SI definition), so the only inaccuracy is the rounding you choose for the final answer.

Can I use these tables offline?

Yes — print this page or save it as a PDF. The tables are computed from exact factors and will not go out of date.