Convert Megameter to Attometer
Convert megameters to attometers instantly. 1 megameter = 1e+24 attometer — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Attometer to Megameter converter for the reverse conversion.
Units explained
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.
Attometer
An attometer is a metric unit of length equal to one quintillionth of a meter (1×10⁻¹⁸ m). It is among the smallest length units in the SI system and is used almost exclusively in particle physics and theoretical work involving sub-nuclear dimensions.
The attometer was defined using the SI prefix atto- (from Danish atten, meaning eighteen), adopted by the Conférence Générale des Poids et Mesures (CGPM) in 1964 to denote one quintillionth (10⁻¹⁸).
Attometers appear in particle physics literature when describing distances comparable to or smaller than nuclear dimensions, including the range of weak nuclear interactions and theoretical Planck-scale ratios. They are rarely encountered outside specialised scientific work.
SI prefix atto- adopted in 1964; the attometer became the standard unit for sub-femtometer measurements in high-energy physics from the late 20th century onward.
Megameter to Attometer conversion formula
The relationship between megameters and attometers:
To convert megameters to attometers, multiply the value in megameters by 1e+24. To reverse, multiply attometers by 1e-24.
How to use this converter
Type a value into the calculator. The result in attometers updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Attometer to Megameter converter for the reverse direction.
Step-by-step: convert megameters to attometers
- Write down the value in megameters (Mm).
- Multiply that value by the factor 1e+24.
- The product is the equivalent value in attometers (am).
- To reverse, multiply the attometer value by 1e-24.
Worked examples
Example 1 — Convert 1 Mm to am:
1 × 1e+24 = 1e+24 am
Example 2 — Convert 100 Mm to am:
100 × 1e+24 = 1e+26 am
Megameter to Attometer conversion table
Standard reference values for converting megameters to attometers:
| Megameter [Mm] | Attometer [am] |
|---|---|
| 0.01 | 1e+22 |
| 0.1 | 1e+23 |
| 1 | 1e+24 |
| 2 | 2e+24 |
| 3 | 3e+24 |
| 4 | 4e+24 |
| 5 | 5e+24 |
| 10 | 1e+25 |
| 20 | 2e+25 |
| 30 | 3e+25 |
| 40 | 4e+25 |
| 50 | 5e+25 |
| 100 | 1e+26 |
| 500 | 5e+26 |
| 1000 | 1e+27 |
Frequently asked questions
How many attometers is 1 megameter?
How do I convert megameters to attometers?
How do I convert attometers back to megameters?
How many attometers is 100 megameters?
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Sources & references
Conversion factor (1 Mm = 1e+24 am) 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 Astronomical Union — System of Astronomical Constants
The IAU defines astronomical units including the AU (149597870700 m exactly) light-year and parsec used in astronomy and astrophysics.