Length Converter

How this length conversion is calculated

Every unit on the page is a multiplier into meters. The result is amount × (meters in the "from" unit) ÷ (meters in the "to" unit). The multipliers in the code are exact definitions, not rounded approximations: millimeter 0.001, centimeter 0.01, meter 1, kilometer 1000, inch 0.0254, foot 0.3048, yard 0.9144, mile 1609.344, nautical mile 1852. The inch, foot, and yard are the international definitions from the 1959 yard-and-pound agreement: 1 inch = 25.4 millimeters exactly, so 1 foot = 0.3048 meters and 1 yard = 0.9144 meters. The mile on this page is 5,280 of those feet, which is 1609.344 meters exactly. The nautical mile is the international nautical mile of 1852 meters exactly. NIST publishes these conversion factors in Special Publication 811. The panel rounds the final quotient to six decimal places. It does not round the factors first.

There is no area, no volume, and no feet-and-inches parser. A length of 5 feet 10 inches is either 70 inches or 70 ÷ 12 = 5.833333 feet. The field will not read a mixed string.

Worked examples

Example 1: 12 feet to meters and to centimeters

12 × 0.3048 = 3.6576 meters exactly, and six decimal places still show 3.6576. The same 12 feet in centimeters: 12 × 0.3048 ÷ 0.01 = 365.76. A ceiling height written as 12 ft on a US plan is 3.6576 m on a metric plan, before anyone rounds it to 3.66 for a drawing.

Example 2: A 5 kilometer road, and a 26.2 mile road

5 kilometers in miles: 5 × 1000 ÷ 1609.344 = 3.10685596…, which displays as 3.106856 miles. The other direction, 26.2 miles in kilometers: 26.2 × 1609.344 ÷ 1000 = 42.1648128, which displays as 42.164813 kilometers. Both use the international mile of 1609.344 meters. Neither uses the nautical mile.

Example 3: Inches, and the 5-foot-10 trap

32 inches to centimeters: 32 × 0.0254 ÷ 0.01 = 81.28 exactly. 60 inches to centimeters is 152.4 exactly. 70 inches to feet: 70 × 0.0254 ÷ 0.3048 = 5.833333 feet, which is 5 feet 10 inches, because 5 × 12 + 10 = 70. Typing 5.10 in the foot field is 5.10 × 12 = 61.2 inches, not 70. The display for 5.10 feet to inches is 61.2. One extra tenth of a foot is more than an inch, and it is a different height from 5 feet 10 inches.

When to use this

Use it for a single distance: a room dimension, a screen diagonal, a map length in statute miles, a chart length in nautical miles, a height you need in centimeters before a form. Square feet of a floor are the Square Footage Calculator. Board feet of a plank are the Board Feet Calculator, which wants thickness and width in inches and length in feet after you have already made that split. Kitchen cups are volume, on the Cooking Measurement Converter.

The BMI page asks for total inches or for centimeters, not for a decimal like 5.10. Convert 5 feet 10 inches to 70 inches here, or type 70 on the BMI form directly. The BMI Calculator then uses its own formula. This page only supplies the length.

Nautical miles, and the foot this page uses

120 nautical miles to kilometers: 120 × 1852 ÷ 1000 = 222.24 exactly. A statute mile is 1609.344 meters, so the nautical mile is longer by 1852 − 1609.344 = 242.656 meters. Pick the unit the chart printed. This page will not guess from the word "mile."

The foot multiplier is 0.3048, the international foot. NIST's tables use that foot. The older U.S. survey foot is not in this list, and the page will not switch to it for a land-survey coordinate. For a shelf, a height, or a school problem, 0.3048 is the factor the result is using. One meter displays as 3.28084 feet and as 39.370079 inches. One kilometer displays as 0.621371 miles.

Common mistakes

• Typing 5.10 for 5 feet 10 inches. 5.10 feet is 61.2 inches. 5 feet 10 inches is 70 inches, which displays as 5.833333 feet.
• Choosing the statute mile for a nautical chart. 1 nautical mile is 1852 meters. 1 statute mile is 1609.344 meters. The labels in the menu are different.
• Rounding the factor, then multiplying. The page multiplies by the full factor and rounds the result to six decimals. Rounding 0.3048 to 0.30 before you multiply will not match the panel.
• Converting a square or a cube with this tool. 10 feet is 3.048 meters. Ten square feet is not 3.048 square meters. Area is a different page.
• Chaining several rounded results. Convert once, from the unit you measured to the unit you need. Feeding a six-decimal result back in as a new input can move the last digit.
• Using a length tool for wire gauge or for rainfall. A millimeter of wire diameter is a length and will convert. A gauge number and a rainfall rate are not in the menu.

Limitations

Nine units, one direction at a time, six decimal places on output, meters as the only base. No feet-and-inches input, no survey foot, no area, no volume, no speed, and no temperature. Negative lengths convert arithmetically, because the page multiplies whatever number you type. Definitions that can change are not stored here. The inch and the nautical mile are definitions. A product tolerance on a piece of lumber is the manufacturer's, and this page does not know it.

Using the result in the next calculator

One meter displays as 3.28084 feet, and one kilometer displays as 0.621371 miles. Those are rounded quotients. Convert the original measurement once instead of feeding a six-decimal result back in as if you had measured it. A board measured as 2.4 meters has to become feet before the board-foot page will mean what you think: 2.4 ÷ 0.3048 displays as 7.874016 feet. Type feet in that length field. Square footage has the same split. This page will not square a length. A 4 meter side displays as 13.12336 feet and a 5 meter side displays as 16.404199 feet. The area of that room is those two feet, multiplied on the square-footage page. Gallons for a few common rooms, after the sides are in feet, are in how many gallons of paint for a 12x12 room. This page does not compute gallons.

A height headed for BMI is the same kind of handoff. 5 feet 10 inches is 70 inches, which displays as 5.833333 feet. Type 70 inches on the BMI form. Typing this page's output of some other conversion, or typing 5.10, starts the next formula from the wrong length.

FAQ

Is 1 inch exactly 2.54 centimeters?

Yes. The factor in this page is 0.0254 meters, which is 2.54 centimeters and 25.4 millimeters. That is the international inch. NIST Special Publication 811 lists the same factor.

Why does 1 meter show 3.28084 feet, not 3.280839?

1 ÷ 0.3048 is 3.28083989…. The panel rounds to six decimal places, so it shows 3.28084. The factor itself is not rounded before the division.

What do I type for 5 feet 10 inches?

70 inches, or 5.833333 feet. Do not type 5.10. The foot field has no separate inches box.

Which mile does a road race use?

A road mile on this page is the statute mile, 1609.344 meters. Five kilometers displays as 3.106856 miles. A nautical mile is a different menu entry, 1852 meters, and 120 of them display as 222.24 kilometers.

Does this use the U.S. survey foot?

No. Feet are multiplied by 0.3048, the international foot in NIST's conversion tables. Survey coordinates that were published in the older survey foot need that older definition, which this menu does not contain.

Can I convert a height and then compute BMI here?

You can convert the height. BMI is a different formula. The BMI Calculator wants total inches or centimeters, and it applies its own equation after that.

Why is a long chain of conversions slightly off?

Each press rounds to six decimal places. Convert from the original measurement in one step. The factors themselves are exact. The display is not an exact fraction.

Related calculators

• Square Footage Calculator for area, after the lengths are in one unit
• How many gallons of paint for a 12x12 room after the sides are in feet
• Board Feet Calculator
• BMI Calculator
• Weight Converter
• Volume Converter
• Cooking Measurement Converter for cups and spoons