Convert miles to km, feet to metres, inches to cm and 16 other length units with exact factors. Accepts feet and inches such as 5 ft 11 in.
By AdminDrafted with AI writing toolsUpdated Checked examples: 4
1 mi is exactly 1.609344 km.
| Unit | Value | Definition |
|---|---|---|
| metre (m) | 1,609.344 | Base unit |
| kilometre (km) | 1.609344 | 1 km = 1,000 m, exact |
| centimetre (cm) | 160,934.4 | 1 cm = 0.01 m, exact |
| millimetre (mm) | 1,609,344 | 1 mm = 0.001 m, exact |
| micrometre (µm) | 1,609,344,000 | 1 µm = 0.000001 m, exact |
| nanometre (nm) | 1,609,344,000,000 | 1 nm = 1 × 10⁻⁹ m, exact |
| ångström (Å) | 16,093,440,000,000 | 1 Å = 1 × 10⁻¹⁰ m, exact |
| inch (in) | 63,360 | 1 in = 0.0254 m, exact |
| foot (ft) | 5,280 | 1 ft = 0.3048 m, exact |
| yard (yd) | 1,760 | 1 yd = 0.9144 m, exact |
| mile (mi) | 1 | 1 mi = 1,609.344 m, exact |
| nautical mile (nmi) | 0.8689762 | 1 nmi = 1,852 m, exact |
| thou (mil) | 63,360,000 | 1 mil = 0.0000254 m, exact |
| hand | 15,840 | 1 hand = 0.1016 m, exact |
| fathom (ftm) | 880 | 1 ftm = 1.8288 m, exact |
| chain (ch) | 80 | 1 ch = 20.1168 m, exact |
| furlong (fur) | 8 | 1 fur = 201.168 m, exact |
| astronomical unit (au) | 1.07578 × 10⁻⁸ | 1 au = 149,597,870,700 m, exact |
| light-year (ly) | 1.701078 × 10⁻¹³ | 1 ly = 9.4607304725808 × 10¹⁵ m, exact |
| parsec (pc) | 5.215529 × 10⁻¹⁴ | 1 pc = 3.0856775814913672789 × 10¹⁶ m, exact (Defined as 648000/π au (IAU 2015 Resolution B2)) |
| point (typographic) (pt) | 4,561,920 | 1 pt = 0.0254/72 m, exact (Desktop publishing point, 1/72 in) |
| pica (pc (type)) | 380,160 | 1 pc (type) = 0.0254/6 m, exact (12 points, 1/6 in) |
1 mi = 1,609.344 m, exact
1 km = 1,000 m, exact
Both units are defined exactly and the converted mathematical value has a terminating decimal. A displayed result may still be rounded.
Each length unit is defined as a fixed number of metres; a conversion multiplies by the “from” factor and divides by the “to” factor. The imperial units have exact metric values because the 1959 international yard and pound agreement fixed the yard at 0.9144 m, which makes the inch 25.4 mm, the foot 0.3048 m and the mile 1,609.344 m.
The default converts 1 mile: 5,280 ft × 0.3048 m/ft = 1,609.344 m, so 1 mi = 1.609344 km with no rounding. A height typed as “5 ft 11 in” is read as one value and gives 180.34 cm.
Results that never terminate, such as 1 nautical mile = 6,076.115… ft, are labelled as repeating and shown to 12 significant figures. Astronomical units follow the IAU: 1 au = 149,597,870,700 m, and a light-year is the distance light travels in 365.25 days.
Go through the meter: multiply by the length of one starting unit in meters, then divide by the length of one target unit. For 3 yards to centimeters, 3 × 0.9144 m = 2.7432 m, and 2.7432 ÷ 0.01 = 274.32 cm. The method works for any pair of length units.
The inch, foot and yard have exact metric values in NIST's conversion tables. Metric prefixes are powers of ten: NIST's SI prefix reference defines milli as one thousandth and kilo as one thousand. A ≈ sign marks a rounded decimal.
| Conversion | Operation on the input | One-unit example |
|---|---|---|
| Feet to mm | Multiply by 304.8 | 1 ft = 304.8 mm |
| mm to feet | Divide by 304.8 | 1 mm ≈ 0.00328083989501 ft |
| Inches to meters | Multiply by 0.0254 | 1 in = 0.0254 m |
| mm to meters | Divide by 1,000 | 1 mm = 0.001 m |
| Meters to km | Divide by 1,000 | 1 m = 0.001 km |
| km to meters | Multiply by 1,000 | 1 km = 1000 m |
| Feet to yards | Divide by 3 | 1 ft ≈ 0.333333333333 yd |
One foot is exactly 304.8 mm, so multiply feet by 304.8: 2 ft = 609.6 mm. To go from millimeters to feet, divide by 304.8. A wall drawn as 2,400 mm high is about 7.874 ft.
The decimal part of a foot is not a count of inches. 7.874 ft is 7 feet plus 0.874 × 12 ≈ 10.49 inches. For the same reason, 5 ft 11 in is 1,803.4 mm, while 5.11 ft is only 1,557.528 mm.
One inch is exactly 0.0254 m. Multiply inches by 0.0254: 12 in = 0.3048 m, and a 65-inch TV diagonal is 1.651 m. For meters to inches, divide by 0.0254. One meter is about 39.37 inches.
Metric lengths convert by powers of ten. Divide millimeters by 1,000 for meters (1,500 mm = 1.5 m), and divide meters by 1,000 for kilometers (1,500 m = 1.5 km).
Multiply by 1,000 to go the other way: 2.5 km = 2,500 m, and a 42.195 km marathon is 42,195 m.
A larger unit always gives a smaller number for the same length. Use that as a check: one kilometer is a million millimeters, so mixing up mm and km puts the answer off by a factor of one million.
Divide feet by 3. 6 ft = 2 yd, and 300 ft = 100 yd, the length of an American football field between the goal lines. A foot is exactly one third of a yard, so 100 ft is 33 1/3 yd, which appears as 33.3333333333.
5 ft 11 in and 5'11" are both read as one length, 71 inches.3/2 means 1.5 of the starting unit.For a height in feet and whole inches, use the height converter. The mm to inches and inches to mm converters include fractional-inch charts for small parts.
Square units belong in the area converter. The most common pair has its own pages: meters to feet and feet to meters.
Checked against: 1 mi = 5280 ft × 0.3048 m/ft = 1609.344 m (NIST HB 44 App. C, international foot of 1959)
Checked against: 71 in × 2.54 cm/in (1 in = 0.0254 m exactly)
Checked against: 1852 m ÷ (0.3048 m/ft) = 2315000/381 ft, a non-terminating decimal
Checked against: 1 ly = 299792458 m/s × 365.25 d × 86400 s/d; 1 au = 149597870700 m (IAU 2012 B2); ratio 431996825232/6830953
Exactly 1.609344 km. The 1959 international yard and pound agreement set the yard at 0.9144 m, and a mile is 1,760 yards, so 1,760 × 0.9144 m = 1,609.344 m. In the other direction 1 km is 0.621371 miles, which makes a 10 km race 6.21 miles.
Exactly 2.54 cm. The inch has been defined as 25.4 mm since the 1959 international yard and pound agreement (effective 1 July 1959 in the United States, according to NIST), so inch-to-centimetre results are exact, not rounded. A 12-inch ruler is 30.48 cm and a 55-inch screen diagonal is 139.7 cm.
Multiply the feet by 30.48 and the inches by 2.54, then add. For 5 ft 11 in, 5 × 30.48 = 152.4 cm and 11 × 2.54 = 27.94 cm, which gives 180.34 cm. Typing “5 ft 11 in” into the value box does the same sum, and the answer is exact because both factors are defined values.
Yes. A nautical mile is exactly 1,852 m, which is 1.1508 statute miles or 6,076.1 ft. It was chosen to approximate one minute of latitude, so sea and air navigation pair it with the knot, one nautical mile per hour. The statute mile used on roads is 1,609.344 m.
NIST declared it obsolete on 1 January 2023 and replaced it with the international foot of exactly 0.3048 m. The survey foot, 1200/3937 m, is 2 parts per million longer, which adds up to 3.2 mm over a mile. This converter uses the international foot for every foot, yard and mile.
This calculator includes 4 worked examples with independently sourced answers. They run in the test suite, and you can run them here too.