Length Converter

About this Length Converter

The Length Converter translates a measurement between common metric and imperial units using standard conversion factors. It is useful for dimensions, travel distances, construction references and everyday unit comparisons.

Length is one of the most frequently converted measurement types in daily life, from following recipes and furniture dimensions to construction plans and international shipping specifications, and metric-imperial mismatches remain common since the US primarily uses feet and inches while most of the world uses meters and centimeters.

For related tasks, try Area Converter, Weight Converter or Volume Converter.

How to use it

1. Enter the measurement value.
2. Choose the source unit and target unit.
3. Select Convert to view the equivalent measurement.

Practical example

One meter equals 100 centimeters, about 39.37 inches, or about 3.28084 feet. Select the units you need and the converter handles the factor automatically.

A 6-foot-tall person converts to approximately 182.88 centimeters, or 1.8288 meters, illustrating why height is one of the most commonly looked-up length conversions between US and metric-using countries.

Things to double-check

Precision matters more in some contexts than others; rounding a converted length to two decimal places is fine for a rough estimate like room dimensions, but engineering, construction and manufacturing contexts often require more decimal precision to avoid compounding small errors.

Metric and imperial lengths

One inch is exactly 2.54 centimetres, one foot is 0.3048 metres, one yard is 0.9144 metres and one mile is 1.609344 kilometres. A person who is 5 feet 10 inches tall is 70 inches, or 177.8 cm. A marathon of 42.195 km is about 26.2 miles, and a 55 inch television has a screen diagonal of 139.7 cm. Having a few anchors in mind lets you check that a conversion looks right.

Where precision matters

For everyday use two decimals are fine, but trades such as engineering, machining and construction need more. A 0.1 mm error is small on a room but not on a machine part, and a 1 percent error on a 30 m run is 30 cm. Keep the full precision while you calculate and round at the end. Use the units specified on drawings and data sheets rather than converting if you can.

Everyday conversions

Lengths come up when you shop for furniture from abroad, check whether luggage fits airline limits, read a cycle frame size or use a map. Airlines often limit a bag to a total of 158 cm, which is about 62 inches, adding length, width and height. For distances, 5 miles is about 8 km and 10 km is about 6.2 miles. Round conversions for planning and exact values for ordering.

Avoiding errors

Check the unit labels twice, since confusing metres with millimetres, or feet with inches, is a thousand-fold or twelve-fold error. Some units have different regional meanings: the nautical mile is 1,852 metres, and old units such as the US survey foot differ very slightly from the international foot. For surveying and legal land descriptions use the unit defined in the document. If something looks wildly off, estimate the answer first and compare.

Everyday reference lengths

Some reference sizes make conversions easy to check. One metre is about 3.28 feet or 39.37 inches, and one kilometre is about 0.621 miles. An A4 sheet is 21 by 29.7 cm, about 8.27 by 11.69 inches. A credit card is 85.6 by 54 mm, about 3.37 by 2.13 inches. A standard door is about 2 m high, which is a good check for room heights. If a converted figure seems far from what you expect with such a reference, recheck the unit you chose.

Sport and screens

A running track lap of 400 metres is about 0.249 miles, and 100 metres is about 109.4 yards. A football pitch of 105 by 68 metres is about 115 by 74 yards. Screen sizes are given as a diagonal in inches, so a 65 inch television has a diagonal of about 165 cm. Using these familiar objects as references helps you notice a wrong conversion, such as a pitch that comes out as 10 metres long.

Worked examples

A person who is 5 feet 9 inches tall is 69 inches, which is 175.26 centimetres. A distance of 12.5 miles is about 20.12 kilometres. A piece of timber 350 millimetres long is about 13.78 inches, and a run of 3,000 metres is about 1.864 miles. A good approach is to convert to the base unit first, metres for metric and inches or feet for imperial, then to the target unit. Keep several decimal places in the middle of the calculation and round the final answer to the precision you need.

How the units are defined

The metre has been defined since 1983 as the distance light travels in a vacuum in 1/299,792,458 of a second. The international foot has been exactly 0.3048 metres since 1959, and the inch is exactly 25.4 millimetres. A nautical mile is exactly 1,852 metres, based on a minute of latitude. A light-year is about 9.46 trillion kilometres. Because modern definitions link units to fixed constants, conversions between metric and imperial are exact, not approximate, even though decimals may need rounding.

Everyday and travel conversions

Length conversions come up when you buy furniture, check luggage limits, read a bicycle frame size or follow a running plan. A 10 kilometre race is about 6.2 miles, and a marathon is 26.2 miles. Airlines often limit checked bags to a total of about 158 centimetres, or 62 inches, for length plus width plus height. Clothing and shoe sizes use their own scales and are not simple conversions. When a product page shows dimensions in inches and you shop in centimetres, convert before you decide whether it fits, and leave a small margin.

Precision and accumulated error

Small rounding errors add up. If you measure 40 pieces and round each by up to 1 millimetre, the total may be off by as much as 4 centimetres. Measure the whole length where you can instead of adding pieces, and measure twice before you cut. Tape measures can stretch or have worn ends, and temperature changes the length of metal tools slightly. In trades, work in one unit throughout a project, such as millimetres, to avoid conversion mistakes, and write down both units for any measurement you pass on to someone else.

Key terms explained

The metre is the base unit of length in the metric system, and a kilometre is a thousand metres. A centimetre is a hundredth of a metre and a millimetre a thousandth. The inch, foot, yard and mile belong to the imperial and US customary systems. A nautical mile is 1,852 metres. A light-year is the distance light travels in a year. Tolerance is the allowed variation in a measurement, and precision is the number of significant digits.

Rules of thumb and quick checks

An inch is exactly 2.54 centimetres, a foot is 30.48 centimetres and a yard is 91.44 centimetres. A mile is about 1.609 kilometres and a kilometre about 0.621 miles. A metre is about 39.37 inches or 3.28 feet. For quick estimates, multiply miles by 1.6 to get kilometres. Round only at the end of a calculation, and use the same unit throughout a project to avoid mistakes.

Quick reference and sanity checks

These exact values are worth remembering. One inch is exactly 2.54 centimetres, one foot is exactly 0.3048 metres, one yard is exactly 0.9144 metres and one international mile is exactly 1.609344 kilometres. A nautical mile is exactly 1,852 metres. Because a kilometre is about 0.62 of a mile, a quick estimate is to multiply kilometres by 0.6. If you convert metres to feet and the number gets smaller, something is wrong. For construction, tailoring and engineering, keep the unit named in the plan, convert only when needed and round at the end to the precision that the job requires.

Frequently asked questions