Free Engineering Tool
Length Unit Converter
Convert between all major length units instantly. Metric and imperial units shown simultaneously.
All Units
| Unit | = Meters | Notes |
|---|---|---|
| 1 nm | 1×10⁻⁹ m | Nanometer |
| 1 μm | 1×10⁻⁶ m | Micrometer (micron) |
| 1 mil | 2.54×10⁻⁵ m | Thousandth of an inch |
| 1 mm | 0.001 m | Millimeter |
| 1 cm | 0.01 m | Centimeter |
| 1 inch | 0.0254 m | International inch |
| 1 foot | 0.3048 m | 12 inches |
| 1 yard | 0.9144 m | 3 feet |
| 1 m | 1 m | SI base unit |
| 1 km | 1000 m | Kilometer |
| 1 mile | 1609.344 m | Statute mile |
Common Engineering Conversions
| From → To | Multiply by | Example |
|---|---|---|
| mm → inch | 0.03937 | 25.4 mm = 1 inch |
| inch → mm | 25.4 | 1 inch = 25.4 mm |
| m → feet | 3.28084 | 1 m = 3.281 ft |
| feet → m | 0.3048 | 1 ft = 0.3048 m |
| km → miles | 0.62137 | 1 km = 0.621 mi |
| miles → km | 1.60934 | 1 mi = 1.609 km |
| μm → mil | 0.03937 | 25.4 μm = 1 mil |
| mil → μm | 25.4 | 1 mil = 25.4 μm |
Handy Memorization Tips
- 1 inch = 25.4 mm (exact, by international agreement since 1959)
- 1 foot = 12 inches = 304.8 mm
- 1 meter ≈ 39.37 inches ≈ 3 ft 3⅜ in
- 1 mile ≈ 1.6 km (for quick estimation: divide km by 8, multiply by 5)
- 1 mil (thou) = 0.001 inch = 25.4 μm (used for paint/coating thickness and shim sizes)
- 1 micron (μm) = 0.001 mm (surface roughness, bearing clearances)
Application-Specific Units
- Surface roughness: Usually in μm (Ra) or μin (microinch)
- Bearing clearance: μm or mil (thou)
- Shaft alignment: mm or mil
- Pipe sizes: DN (mm) in metric, NPS (inches) in imperial
- Sheet metal: mm or gauge number
- Wire diameter: mm or AWG (American Wire Gauge)
- Vibration displacement: μm peak-to-peak or mil peak-to-peak
- Machining tolerances: μm or 0.001 mm, often expressed as IT grades (ISO 286)
Historical Note
The meter was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole. Since 1983, it is defined as the distance light travels in vacuum in 1/299,792,458 of a second, making it the most precisely defined SI base unit.
Nominal pipe sizes do not correspond directly to any measured dimension. This table cross-references the metric DN and imperial NPS designations along with actual outside diameters.
| DN (mm) | NPS (inch) | Actual OD (mm) | Actual OD (inch) |
|---|---|---|---|
| 6 | ⅛ | 10.3 | 0.405 |
| 8 | ¼ | 13.7 | 0.540 |
| 10 | ⅜ | 17.1 | 0.675 |
| 15 | ½ | 21.3 | 0.840 |
| 20 | ¾ | 26.7 | 1.050 |
| 25 | 1 | 33.4 | 1.315 |
| 32 | 1¼ | 42.2 | 1.660 |
| 40 | 1½ | 48.3 | 1.900 |
| 50 | 2 | 60.3 | 2.375 |
| 65 | 2½ | 73.0 | 2.875 |
| 80 | 3 | 88.9 | 3.500 |
| 100 | 4 | 114.3 | 4.500 |
| 150 | 6 | 168.3 | 6.625 |
| 200 | 8 | 219.1 | 8.625 |
| 250 | 10 | 273.0 | 10.750 |
| 300 | 12 | 323.9 | 12.750 |
Professional engineering calculators and measurement instruments.
Nikolai Shelkovenko
Nikolai Shelkovenko is a vibration analysis engineer and the founder and CEO of Vibromera. For more than 15 years he has balanced rotating equipment in the field rather than on a test bench: mulchers, industrial fans, crushers, centrifuges, shafts and spindles. That work is what the Balanset instruments grew out of — they were designed as a tool a specialist can carry to the machine and use alone, on site, not as laboratory equipment. Vibromera was founded in 2017 and has been based in Porto, Portugal, since 2023. Development, assembly and support of the Balanset line all happen here. The flagship instrument is the Balanset-1A, a portable analyser for single- and two-plane balancing and for vibration diagnostics. Nikolai is personally involved in customer support, in working through difficult balancing cases and in the development of the software. He works with customers worldwide, in any language.
