Convert Inch to Earth's Polar Radius
Convert inches to earth's polar radii instantly. 1 inch = 3.995751e-9 earth's polar radius — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Earth's Polar Radius to Inch converter for the reverse conversion.
Units explained
Inch
An inch is an Imperial and US customary unit of length defined since 1959 as exactly 25.4 millimeters (0.0254 meters). It is still the standard small unit of length in the United States, the United Kingdom (informally), and a few other countries.
The inch derives from the Roman uncia (one-twelfth of a foot) and survived through Anglo-Saxon and medieval English measurement systems. Various definitions persisted regionally until the 1959 International Yard and Pound Agreement standardized the inch globally as exactly 25.4 mm.
Inches are used in the US and UK for body height, screen sizes (TVs, monitors, phones), tire sizes, plumbing, lumber, paper sizes (US Letter is 8.5 × 11 in), and most consumer product specifications in the United States.
Anglo-Saxon origin (predating 1066); standardized to 25.4 mm exactly by the International Yard and Pound Agreement of 1959, signed by the US, UK, Canada, Australia, New Zealand, and South Africa.
Earth's Polar Radius
Earth's polar radius is the distance from the planet's center to either pole, approximately 6,356,752 meters under the WGS84 geodetic reference system. The polar radius is about 21 km shorter than the equatorial radius due to Earth's oblate spheroid shape.
Derived from WGS84's flattening parameter (f ≈ 1/298.257); the difference from the equatorial radius is the geometric signature of Earth's rotational oblateness.
Earth's polar radius is used in geodesy, satellite-orbit calculations, and global cartography. Together with the equatorial radius it defines Earth's reference ellipsoid in WGS84.
Derived from the WGS84 reference ellipsoid adopted in 1984; the value is computed from the equatorial radius minus the oblateness.
Inch to Earth's Polar Radius conversion formula
The relationship between inches and earth's polar radii:
To convert inches to earth's polar radii, multiply the value in inches by 3.995751e-9. To reverse, multiply earth's polar radii by 2.502658e+8.
How to use this converter
Type a value into the calculator. The result in earth's polar radii updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Earth's Polar Radius to Inch converter for the reverse direction.
Step-by-step: convert inches to earth's polar radii
- Write down the value in inches (in).
- Multiply that value by the factor 3.995751e-9.
- The product is the equivalent value in earth's polar radii (R⊕,p).
- To reverse, multiply the earth's polar radius value by 2.502658e+8.
Worked examples
Example 1 — Convert 1 in to R⊕,p:
1 × 3.995751e-9 = 3.995751e-9 R⊕,p
Example 2 — Convert 100 in to R⊕,p:
100 × 3.995751e-9 = 3.995751e-7 R⊕,p
Real-world example — Ruler-scale measurements
A 30-inch school ruler converts cleanly to earth's polar radii — useful when buying a desk accessory from a retailer whose product specs use a different unit.
30 in × 3.995751e-9 = 1.198725e-7 R⊕,p
Real-world example — Hardware-scale dimensions
A 10-inch fastener or component is about as long as a thumbnail. Mechanics and DIY enthusiasts convert between inches and earth's polar radii daily when mixing metric and imperial tools.
10 in × 3.995751e-9 = 3.995751e-8 R⊕,p
Real-world example — Postcard and small-object dimensions
A postcard is about 5 inches wide. Converting to earth's polar radii is essential for international postal addressing forms that ask for dimensions in different units across countries.
5 in × 3.995751e-9 = 1.997876e-8 R⊕,p
Inch to Earth's Polar Radius conversion table
Standard reference values for converting inches to earth's polar radii:
| Inch [in] | Earth's Polar Radius [R⊕,p] |
|---|---|
| 0.01 | 3.995751e-11 |
| 0.1 | 3.995751e-10 |
| 1 | 3.995751e-9 |
| 2 | 7.991503e-9 |
| 3 | 1.198725e-8 |
| 4 | 1.598301e-8 |
| 5 | 1.997876e-8 |
| 10 | 3.995751e-8 |
| 20 | 7.991503e-8 |
| 30 | 1.198725e-7 |
| 40 | 1.598301e-7 |
| 50 | 1.997876e-7 |
| 100 | 3.995751e-7 |
| 500 | 1.997876e-6 |
| 1000 | 3.995751e-6 |
Frequently asked questions
How many earth's polar radii is 1 inch?
How do I convert inches to earth's polar radii?
How do I convert earth's polar radii back to inches?
How many earth's polar radii is 100 inches?
Popular length unit conversions
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Metric / SI (18 units)
Imperial / US Customary (26 units)
Nautical (1 units)
Astronomical (9 units)
Atomic / Physics (6 units)
Typographic (3 units)
Sources & references
Conversion factor (1 in = 3.995751e-9 R⊕,p) 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.