Length and distance measure the 1-dimensional extent between two spatial points. Across architecture, construction, aviation, engineering, manufacturing, nanotech, and astrophysics, distance measurement relies on two primary standards: the International System of Units (SI metric: meters, kilometers, centimeters, millimeters, nanometers) and US Customary / Imperial units (inches, feet, yards, statute miles, nautical miles). Specialized scientific fields also utilize angstroms (Å), Planck lengths, astronomical units (AU), light years (ly), and parsecs (pc).
Our free online Length Converter provides instant, high-precision conversions across all metric, imperial, maritime, micro-scale, and cosmic distance units:
- Inches to Centimeters: Multiply inches by
2.54(exact 1959 International Yard standard: 1 in = 2.54 cm = 25.4 mm). - Feet to Meters: Multiply feet by
0.3048(1 ft = 0.3048 m = 30.48 cm). - Yards to Meters: Multiply yards by
0.9144(1 yd = 0.9144 m = 3 ft = 36 in). - Kilometers to Miles: Multiply km by
0.62137119(1 mi = 1,609.344 m = 1.609344 km = 5,280 ft). - Nautical Miles to Kilometers: Multiply NM by
1.852(1 NM = 1,852 m = 1.150779 miles). - Light Years to Kilometers:
1 light year = 9,460,730,472,580 km(≈ 9.461 trillion km).
Master Length & Distance Unit Conversion Table
The table below displays exact physical relationships, SI power multipliers, and US Customary equivalents relative to 1 Meter (m):
| Length Unit Name | Symbol | Exact Value in Meters (m) | US Customary / Imperial Equivalent | Domain & System Standard |
|---|---|---|---|---|
| 1 Meter | m |
1.0 m |
3.280840 ft (39.370079 in / 1.093613 yd) | SI Base Unit (Speed of Light Definition) |
| 1 Kilometer | km |
1,000.0 m (103 m) | 0.621371 miles (3,280.84 ft) | SI Metric Geographic Distance |
| 1 Centimeter | cm |
0.01 m (10-2 m) | 0.393701 inches | SI Metric Everyday Human Scale |
| 1 Millimeter | mm |
0.001 m (10-3 m) | 0.039370 inches (39.37 mils) | Engineering & Manufacturing Precision |
| 1 Micrometer (Micron) | μm, μ |
0.000001 m (10-6 m) | 0.00003937 inches (39.37 microinches) | Cell Biology & Optics Scale |
| 1 Nanometer | nm |
1.0 × 10-9 m | 10 Angstroms (Å) | Semiconductor Microchip & Molecular Scale |
| 1 Angstrom | Å |
1.0 × 10-10 m | 0.1 nanometers (100 picometers) | Crystallography & Atomic Physics Scale |
| 1 Inch (International) | in, " |
0.0254 m (exact) |
1.0 in (2.54 cm = 25.4 mm) |
1959 International Yard Agreement Standard |
| 1 Foot (International) | ft, ' |
0.3048 m (exact) |
12.0 in (30.48 cm) |
US Customary / Imperial Architecture Standard |
| 1 Yard (International) | yd |
0.9144 m (exact) |
3.0 ft (36.0 in / 91.44 cm) |
US Customary / Imperial Field Measurement |
| 1 Statute Mile | mi |
1,609.344 m (exact) |
5,280 ft (1,760 yd / 1.609344 km) |
US / UK Road Driving Distance |
| 1 Nautical Mile (International) | NM, nmi |
1,852.0 m (exact) |
6,076.115 ft (1.150779 statute miles) | Aviation & Maritime Navigation (1′ latitude arc) |
| 1 Fathom | fath |
1.8288 m (exact) |
6.0 ft (2 yd) |
Traditional Nautical Water Depth |
| 1 Furlong | fur |
201.168 m (exact) |
660 ft (220 yd / 10 chains / 1/8 mile) |
Horse Racing & Agricultural Land Surveying |
| 1 Survey Chain (Gunter’s) | ch |
20.1168 m (exact) |
66 ft (4 rods / 100 links) |
Public Land Survey System (PLSS) |
| 1 Rod (Perch or Pole) | rd |
5.0292 m (exact) |
16.5 ft (5.5 yd / 1/4 chain) |
Traditional Land Survey Unit |
| 1 Astronomical Unit | AU |
149,597,870,700 m (exact) |
92,955,807 miles (149.598 million km) | Solar System Astronomy (Earth-Sun Distance) |
| 1 Light Year | ly |
9.46073047 × 1015 m | 5.878625 × 1012 miles (63,241 AU) | Interstellar Deep Space Distance |
| 1 Parsec | pc |
3.08567758 × 1016 m | 19.173512 × 1012 miles (3.26156 ly / 206,265 AU) | Astrophysical Parallax Measurement Standard |
Step-by-Step Calculation Example
To convert 100 Meters to Feet and Inches:
100 m ÷ 0.3048 = 328.0839895 Feet
0.0839895 ft × 12 inches/ft = 1.00788 inches
Thus, 100 meters is equal to exactly 328 feet, 1.01 inches (328.08 ft or 109.36 yards).
Real-World Physical Scale & Distance Benchmarks
Below is a comparative reference chart showing distances across subatomic, biological, human engineering, planetary, and galactic scales:
| Physical Scale / Object | Distance in Metric Units | Distance in US Customary / Astronomical | Scientific & Everyday Context |
|---|---|---|---|
| Planck Length (ℓP) | 1.616 × 10-35 m | 6.36 × 10-34 inches | Smallest possible physical quantum unit of length |
| Proton Radius (Atomic Nucleus) | 0.841 femtometers (fm) | 8.41 × 10-14 cm | Radius of a single hydrogen atomic nucleus |
| Human DNA Double Helix Width | 2.0 nanometers (nm) | 20 Angstroms (Å) | Diameter of the human genetic DNA strand |
| Single Human Red Blood Cell | 7.0 micrometers (μm) | 0.000276 inches | Diameter of a mature human erythrocyte cell |
| Credit Card Thickness | 0.76 millimeters (mm) | 0.030 inches (30 mils) | Standard ISO 7810 ID card thickness specification |
| American Football Field Length | 91.44 meters (m) | 100 yards (300 feet) | Standard gridiron field goal line to goal line distance |
| Marathon Race Distance | 42.195 kilometers (km) | 26 miles, 385 yards (26.219 mi) | Official Olympic marathon running race length |
| Earth Equatorial Circumference | 40,075 kilometers (km) | 24,901 statute miles | Full rotational perimeter around Earth’s equator |
| Distance to Proxima Centauri | 4.017 × 1013 km | 4.246 light years (1.302 parsecs) | Distance from Earth to nearest neighboring star system |
History & Standards: 1959 International Yard Agreement vs. French Meridian Meter
The 1791 French Light-Speed Meter Definition
The metric system was established during the French Revolution in 1791. The meter (m) was originally defined by the French Academy of Sciences as 1 / 10,000,000 of the distance from the Earth’s equator to the North Pole along the Paris meridian. In 1983, the 17th CGPM redefined the meter based on an exact fundamental physical constant: the distance traveled by light in a vacuum in 1 / 299,792,458 of a second.
The 1959 International Yard and Pound Agreement
Before 1959, the United States, United Kingdom, Canada, Australia, and New Zealand maintained slightly conflicting definitions of the inch and foot based on individual national prototype yards. On July 1, 1959, the six nations signed the International Yard and Pound Agreement, unifying the inch to exactly 25.4 millimeters (1 in = 2.54 cm) and the yard to exactly 0.9144 meters. This established absolute physical compatibility between US Customary and SI metric lengths.
Popular direct conversions:
- Centimeters to Inches Converter | Inches to Centimeters Converter
- Millimeters to Inches Converter | Inches to Millimeters Converter
- Meters to Feet Converter | Feet to Meters Converter
- Kilometers to Miles Converter | Miles to Kilometers Converter
- Centimeters to Feet Converter | Feet to Centimeters Converter
- Inches to Feet Converter | Feet to Inches Converter
- Conversion Calculator Main Directory
Frequently Asked Questions (FAQ)
How many centimeters (cm) are in 1 inch?
There are exactly 2.54 centimeters (25.4 mm) in 1 inch under the 1959 International Yard Agreement.
How many feet (ft) are in 1 meter (m)?
There are approximately 3.28084 feet in 1 meter (or 3 feet 3.37 inches).
How many kilometers (km) are in 1 mile?
There are exactly 1.609344 kilometers in 1 statute mile (or ~1.61 km).
What is the difference between a statute mile and a nautical mile?
A statute mile is used for land travel in the US/UK and equals 5,280 feet (1,609.344 meters). A nautical mile (NM) is used in aviation and maritime navigation, defined as 1 minute of arc of latitude on Earth, which equals exactly 1,852 meters (6,076.115 feet).