Length Converter

Measurement

Free online length converter. Instantly convert between millimetres, centimetres, metres, kilometres, inches, feet, yards, miles, and nautical miles.

From

All conversionsfor 1 Kilometres (km)

Millimetres (mm)	1000000
Centimetres (cm)	100000
Metres (m)	1000
Kilometres (km)	1
Inches (in)	39370.079
Feet (ft)	3280.8399
Yards (yd)	1093.6133
Miles (mi)	0.62137119
Nautical Miles	0.5399568

What is a Length?

A length converter is a tool that translates a measurement in one unit of length into its exact equivalent in another unit. Length — the measure of distance between two points — is expressed differently across unit systems, and these systems coexist in everyday Indian life. Road signs and vehicle odometers use kilometres, height on Aadhaar and medical forms appears in centimetres or feet-and-inches, fabric merchants measure in metres, engineering drawings use millimetres, and imported content from the United States references inches, feet, and miles.

The length converter on this page handles the full range of metric and imperial length units: millimetres (mm), centimetres (cm), metres (m), kilometres (km), inches (in), feet (ft), yards (yd), miles (mi), and nautical miles. Conversion between any two is immediate and bidirectional — enter a value in either field, and the other updates instantly without any button press.

All length conversions are linear, meaning they involve a single multiplication by a fixed factor relative to a common base (the metre). There are no special cases, offsets, or formula branches, unlike temperature where Celsius–Fahrenheit conversion requires an additive step. This makes length one of the most straightforward families of unit conversion. The reference table below the converter shows the current input value expressed in every supported unit simultaneously, which is useful when you need to compare across systems at a glance.

For related conversions in the measurement category, you may also need the Weight & Mass Converter if your project involves both dimensional and mass specifications.

How to use this Length calculator

Select your From unit — use the left unit dropdown. Units are grouped into Metric (mm, cm, m, km), Imperial (in, ft, yd, mi), and Other (nautical miles). The default opens at Kilometres.
Enter your value in the left input field. Type any number — decimals and large values are supported. The To field updates immediately.
Select your To unit — use the right unit dropdown. The default is Miles. Change it to any other unit and the result recalculates instantly.
Type in the To field if you want to work backwards — for example, enter 100 miles and see the kilometre equivalent appear in the From field. The conversion is fully bidirectional.
Swap the units using the arrow button between the two panels. This reverses From and To while keeping the current value, so 5 km → 3.11 mi becomes 5 mi → 8.05 km in one click.
Read the reference table below the converter for a full breakdown of the current value expressed in all supported units. The active unit is highlighted, and the numbers use monospace formatting for easy comparison.
Share or bookmark the result — the URL in your browser reflects the current state. Copy and share it directly.

Formula & Methodology

All length conversions use a single two-step formula via a common base unit (metre):

Result = (Input × F_from) ÷ F_to

Where:
- Input — the value entered in the From field
- F_from — the conversion factor of the From unit to metres (toBase)
- F_to — the conversion factor of the To unit to metres (toBase)
- Result — the converted value in the To unit

Unit conversion factors (toBase, in metres):

- mm = 0.001
- cm = 0.01
- m = 1 (base)
- km = 1,000
- in = 0.0254
- ft = 0.3048
- yd = 0.9144
- mi = 1,609.344
- nmi = 1,852

Worked example — Convert 42.195 km (marathon distance) to miles:

Result = (42.195 × 1,000) ÷ 1,609.344
Result = 42,195 ÷ 1,609.344
Result ≈ 26.219 miles

The standard marathon distance is 26.219 miles — the formula confirms the exact IAAF-defined length of 42.195 km.

Worked example — Convert 5 feet 9 inches to centimetres (Indian height conversion):

Step 1: Convert to a single unit — 5 ft 9 in = (5 × 12) + 9 = 69 inches
Step 2: Result = (69 × 0.0254) ÷ 0.01 = 1.7526 ÷ 0.01 = 175.26 cm

A person who is 5 ft 9 in tall is 175.26 cm — a common entry on Indian health and ID forms.

Precision note: All factors are exact by international definition (the inch has been defined as exactly 25.4 mm since 1959). The nautical mile is defined as exactly 1,852 m by the International Hydrographic Organization. No approximations are used in this converter.

Frequently Asked Questions

What is a length converter and how does it work?

A length converter is an online tool that instantly transforms a measurement in one unit into its equivalent in another unit — for example, converting kilometres to miles or centimetres to inches. It works by applying a fixed conversion factor specific to each pair of units, using metres as the common base. You type a value in any field and the result updates immediately, with no manual arithmetic required.

How many metres are in a kilometre?

There are exactly 1,000 metres in one kilometre. The prefix 'kilo-' in the metric system always denotes a factor of 1,000. So 5 km = 5,000 m, and conversely, 500 m = 0.5 km. This relationship is used routinely in road distances, running events like the 5K and 10K, and maps across India and internationally.

How do I convert kilometres to miles?

To convert kilometres to miles, multiply the kilometre value by 0.621371. For example, 100 km × 0.621371 = 62.1371 miles. In everyday use, a quick approximation is to multiply by 0.625 (or divide by 1.6), which gives a result accurate to within 1%. Our length converter handles the exact calculation instantly.

What is the difference between metres and yards?

A metre (metric system) and a yard (imperial system) are close in size but not equal. One metre equals approximately 1.0936 yards, meaning a metre is about 9.4% longer than a yard. In cricket, pitch dimensions are traditionally quoted in yards (22 yards = 1 chain = 1 cricket pitch), while athletics tracks use metres, making this a common conversion in Indian sports contexts.

How many inches are in a foot?

There are exactly 12 inches in one foot. This is a fixed, internationally defined relationship. One foot equals 30.48 cm or 0.3048 m. Heights in India are often expressed in feet and inches (for example, 5 feet 9 inches = 175.26 cm), making this a frequent conversion for medical forms, property listings, and personal records.

What is the formula for length conversion?

All metric-to-metric and metric-to-imperial length conversions use the formula: Result = (Input × toBase_fromUnit) ÷ toBase_toUnit, where toBase is each unit's conversion factor relative to the metre. For example, to convert 5 miles to kilometres: (5 × 1609.344) ÷ 1000 = 8.04672 km. Non-linear unit systems do not exist in length — all conversions are purely multiplicative.

How do I convert centimetres to inches?

Divide the centimetre value by 2.54 (since 1 inch = 2.54 cm exactly). For example, 175 cm ÷ 2.54 = 68.9 inches = 5 feet 8.9 inches. This is one of the most common conversions in India, where clothing sizes, height on government forms, and medical records may appear in either unit. Our length converter shows the result instantly when you select cm and inches.

What is a nautical mile and when is it used?

A nautical mile is defined as 1,852 metres (exactly), corresponding to one minute of arc of latitude on the Earth's surface. It is used in maritime navigation and aviation, where distances and speeds (knots = nautical miles per hour) are measured in nautical units. India's coastal shipping and the Indian Navy use nautical miles for navigation and jurisdiction boundaries like the Exclusive Economic Zone (EEZ).

Which is longer — a mile or a kilometre?

A mile is longer than a kilometre. One mile equals 1.609344 km, so a mile is approximately 61% longer than a kilometre. Historically, India used miles under British rule and switched to kilometres after metrication in the 1960s–70s. Today, Indian road signs and odometers use kilometres, while older literature and imported vehicles may reference miles.

How do I convert feet to metres for construction use in India?

Multiply the feet value by 0.3048 to get metres. For example, a 10-foot ceiling is 10 × 0.3048 = 3.048 m. Indian construction drawings often mix both systems — floor plans may show dimensions in feet while structural engineers work in metres per IS codes. Our length converter lets you switch between them instantly so you never misread a measurement on site.

Can I convert millimetres to centimetres using this tool?

Yes. Select Millimetres as the From unit and Centimetres as the To unit, then enter your value. The conversion is simple: divide by 10 (since 1 cm = 10 mm). For example, 250 mm = 25 cm. Millimetres and centimetres are used widely in Indian engineering drawings, fabric measurements, and hardware specifications like screw diameters and pipe sizes.

What units does the length converter support?

The converter supports nine units across three groups: Metric (millimetres, centimetres, metres, kilometres), Imperial (inches, feet, yards, miles), and Other (nautical miles). All units are bidirectional — you can type in either the From or To field and the other updates immediately. The reference table below the converter shows all unit equivalents simultaneously for the current input value.