Convert Kilometer to Gigameter
Convert kilometers to gigameters instantly. 1 kilometer = 1e-6 gigameter — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Gigameter 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.
Gigameter
A gigameter is a metric unit of length equal to one billion meters (1×10⁹ m). It is most often used in astronomy and astrophysics when expressing distances within the inner solar system.
The gigameter uses the SI prefix giga- (from Greek gigas, giant), adopted by the CGPM in 1960 to denote multiplication by one billion (10⁹).
Gigameters are used to express distances such as the Sun's diameter (~1.39 Gm), the Earth–Moon distance (~0.384 Gm), and similar inner-solar-system scales. Astronomical units and light-seconds are also common for these distances.
SI prefix giga- adopted in 1960; the gigameter became standard in astronomy for sub-AU distances by the late 20th century.
Kilometer to Gigameter conversion formula
The relationship between kilometers and gigameters:
To convert kilometers to gigameters, multiply the value in kilometers by 1e-6. To reverse, multiply gigameters by 1000000.
How to use this converter
Type a value into the calculator. The result in gigameters updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Gigameter to Kilometer converter for the reverse direction.
Step-by-step: convert kilometers to gigameters
- Write down the value in kilometers (km).
- Multiply that value by the factor 1e-6.
- The product is the equivalent value in gigameters (Gm).
- To reverse, multiply the gigameter value by 1000000.
Worked examples
Example 1 — Convert 1 km to Gm:
1 × 1e-6 = 1e-6 Gm
Example 2 — Convert 100 km to Gm:
100 × 1e-6 = 1e-4 Gm
Real-world example — Road-sign distances across systems
A 100-kilometer road sign converts cleanly into gigameters — exactly the conversion drivers planning trips abroad rely on when reading road signs in a different measurement system.
100 km × 1e-6 = 1e-4 Gm
Real-world example — Endurance race distances
A 50-kilometer cycling or running race converts to a recognizable distance in gigameters. Endurance athletes coming from a different measurement system use this conversion to compare training plans across regions.
50 km × 1e-6 = 5e-5 Gm
Real-world example — Maritime exclusion zone
A 200-kilometer exclusion zone (a common maritime boundary) converts to a different value in gigameters that's useful when describing the same zone in everyday land-distance units.
200 km × 1e-6 = 0.0002 Gm
Kilometer to Gigameter conversion table
Standard reference values for converting kilometers to gigameters:
| Kilometer [km] | Gigameter [Gm] |
|---|---|
| 0.01 | 1e-8 |
| 0.1 | 1e-7 |
| 1 | 1e-6 |
| 2 | 2e-6 |
| 3 | 3e-6 |
| 4 | 4e-6 |
| 5 | 5e-6 |
| 10 | 1e-5 |
| 20 | 2e-5 |
| 30 | 3e-5 |
| 40 | 4e-5 |
| 50 | 5e-5 |
| 100 | 1e-4 |
| 500 | 0.0005 |
| 1000 | 0.001 |
Frequently asked questions
How many gigameters is 1 kilometer?
How do I convert kilometers to gigameters?
How do I convert gigameters back to kilometers?
How many gigameters is 100 kilometers?
Popular length unit conversions
Convert Kilometer to other length units
Show all Kilometer conversions
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 = 1e-6 Gm) 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.