Convert Kilometer to Megameter
Convert kilometers to megameters instantly. 1 kilometer = 0.001 megameter — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Megameter to Kilometer converter for the reverse conversion.
Units explained
Kilometer
A kilometer is a metric unit of length equal to one thousand meters. It is the standard unit for measuring road distances, geographic distances, and other large-scale measurements in metric countries.
The kilometer was defined alongside the meter in 1795 using the standard SI prefix kilo- (from Greek chilioi, "thousand"), denoting one thousand units.
Kilometers are used worldwide (except the United States and a few others) for road signage, geographic distance, athletic events, and scientific distances at planetary scale. Speed limits in most countries are given in km/h.
Adopted 1795 in France as part of the original metric system; the kilometer became the global standard for road and geographic distance through the 19th and 20th century metric adoption.
Megameter
A megameter is a metric unit of length equal to one million meters (1×10⁶ m, or 1,000 km). It is occasionally used in geophysics and astronomy when expressing planetary-scale distances in SI units.
The megameter uses the SI prefix mega- (from Greek megas, great), adopted by the CGPM in 1960 to denote multiplication by one million.
Megameters appear in geophysics (Earth's mean radius is 6.371 Mm), planetary science, and large-scale civil engineering planning. The unit is less common than the kilometer for everyday geographic distances.
SI prefix mega- adopted in 1960; the megameter is the standard SI prefix unit for distances comparable to planetary radii.
Kilometer to Megameter conversion formula
The relationship between kilometers and megameters:
To convert kilometers to megameters, multiply the value in kilometers by 0.001. To reverse, multiply megameters by 1000.
How to use this converter
Type a value into the calculator. The result in megameters updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Megameter to Kilometer converter for the reverse direction.
Step-by-step: convert kilometers to megameters
- Write down the value in kilometers (km).
- Multiply that value by the factor 0.001.
- The product is the equivalent value in megameters (Mm).
- To reverse, multiply the megameter value by 1000.
Worked examples
Example 1 — Convert 1 km to Mm:
1 × 0.001 = 0.001 Mm
Example 2 — Convert 100 km to Mm:
100 × 0.001 = 0.1 Mm
Real-world example — Road-sign distances across systems
A 100-kilometer road sign converts cleanly into megameters — exactly the conversion drivers planning trips abroad rely on when reading road signs in a different measurement system.
100 km × 0.001 = 0.1 Mm
Real-world example — Endurance race distances
A 50-kilometer cycling or running race converts to a recognizable distance in megameters. Endurance athletes coming from a different measurement system use this conversion to compare training plans across regions.
50 km × 0.001 = 0.05 Mm
Real-world example — Maritime exclusion zone
A 200-kilometer exclusion zone (a common maritime boundary) converts to a different value in megameters that's useful when describing the same zone in everyday land-distance units.
200 km × 0.001 = 0.2 Mm
Kilometer to Megameter conversion table
Standard reference values for converting kilometers to megameters:
| Kilometer [km] | Megameter [Mm] |
|---|---|
| 0.01 | 1e-5 |
| 0.1 | 0.0001 |
| 1 | 0.001 |
| 2 | 0.002 |
| 3 | 0.003 |
| 4 | 0.004 |
| 5 | 0.005 |
| 10 | 0.01 |
| 20 | 0.02 |
| 30 | 0.03 |
| 40 | 0.04 |
| 50 | 0.05 |
| 100 | 0.1 |
| 500 | 0.5 |
| 1000 | 1 |
Frequently asked questions
How many megameters is 1 kilometer?
How do I convert kilometers to megameters?
How do I convert megameters back to kilometers?
How many megameters is 100 kilometers?
Popular length unit conversions
Convert Kilometer to other length units
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Metric / SI (17 units)
Imperial / US Customary (27 units)
Nautical (1 units)
Astronomical (9 units)
Atomic / Physics (6 units)
Typographic (3 units)
Sources & references
Conversion factor (1 km = 0.001 Mm) verified against the following authoritative sources:
- BIPM — The International System of Units (SI Brochure 9th ed.)
Official BIPM publication defining the seven SI base units (including the meter) and the rules for their use. The global authority on units of measurement.
- NIST — Guide to the SI
US National Institute of Standards and Technology reference covering the SI base and derived units with definitions and usage rules for US technical practice.
- NIST Special Publication 811 — Guide for the Use of the International System of Units
Detailed NIST guide covering exact conversion factors between SI and US customary units along with formatting and rounding conventions.
- NIST — Refinement of values for the yard and pound (Federal Register 1959)
The treaty (signed by US
- International Hydrographic Organization — Resolution on the Nautical Mile
International authority that standardised the nautical mile at exactly 1852 m in 1929 — the value adopted worldwide for sea and air navigation.