Length Converter

How the Length Converter Works

A length converter changes a measurement from one unit of distance into another using fixed, internationally agreed conversion factors. Every common length unit can be expressed in terms of the metre, the SI base unit of length, so the converter first turns your value into metres and then into the unit you want.

The metric system is built on powers of ten, which makes those conversions simple. One kilometre equals 1,000 metres, one centimetre equals 0.01 metre, and one millimetre equals 0.001 metre. Imperial and US customary units connect to the metric system through exact definitions: 1 inch = 2.54 centimetres exactly, which is the anchor for all the larger imperial units.

From that single exact figure, the rest follow: 1 foot = 12 inches = 30.48 cm, 1 yard = 3 feet = 0.9144 m, and 1 mile = 1,760 yards = 1,609.344 m (about 1.609 km). To convert manually, multiply by the factor that links the two units; to go the other way, divide by it.

Common Length Conversion Factors

The table below lists the conversion factors people search for most often. Use it as a quick reference or to sanity-check the calculator's output.

From	To	Multiply by
1 inch	centimetres	2.54
1 foot	metres	0.3048
1 yard	metres	0.9144
1 mile	kilometres	1.609344
1 metre	feet	3.28084
1 kilometre	miles	0.621371
1 centimetre	inches	0.393701

For example, to convert 5 miles to kilometres, multiply 5 by 1.609344 to get 8.04672 km. To convert 100 cm to inches, multiply 100 by 0.393701 to get 39.37 inches.

Metric vs Imperial Units

Most of the world uses the metric system (metres, centimetres, kilometres), while the United States and, informally, the United Kingdom still rely on imperial units (inches, feet, yards, miles). Knowing how to switch between them is essential for travel, construction, sewing, science homework and international shipping.

• Small lengths such as screen sizes or fabric are usually given in inches or centimetres.
• Human height appears in feet and inches in the US but in centimetres elsewhere (5 ft 9 in is about 175 cm).
• Road distances use miles in the US and UK but kilometres almost everywhere else.
• Engineering and science default to metres and millimetres for precision.

Because the inch is defined exactly as 2.54 cm, conversions between the two systems are precise rather than approximate, so you can rely on the numbers above for any everyday or professional task.

Tips for Converting Length Accurately

While the calculator does the maths for you, understanding a few practical points helps you trust and double-check the results, especially when accuracy matters in construction, tailoring or science.

• Keep the direction straight. Multiplying when you should divide is the most common mistake. If you are going from a larger unit to a smaller one (metres to centimetres), the number should get bigger; from smaller to larger (millimetres to metres), it should get smaller.
• Watch significant figures. For everyday use, rounding 1 mile to 1.61 km is fine, but for engineering you may need the full 1.609344. The converter retains full precision so you can round only at the final step.
• Chain conversions carefully. To go from inches to metres, you can convert inches to centimetres (x2.54) then centimetres to metres (divide by 100), or simply multiply inches by 0.0254 directly.
• Mind mixed units. Heights and dimensions are often written as feet-and-inches or metres-and-centimetres. Convert each part separately and add them.

A quick way to estimate in your head: a metre is roughly a long stride or about 3.3 feet, an inch is about two and a half centimetres, and a kilometre is a little over half a mile (0.62). These approximations are handy for travel and shopping, while the exact factors above give you reliable answers whenever precision counts. Bookmark this length converter so the correct factor is always one click away.