Understanding hands to astronomical units Conversion
The hand (hh) is a small imperial length unit equal to exactly 4 inches (10.16 cm), used almost exclusively to measure the height of horses at the withers. The astronomical unit (au) is a vast length defined as exactly 149,597,870,700 meters—the average Earth-Sun distance—used to describe distances within solar systems. Converting between them is an extreme change of scale that mostly serves as an illustrative or educational exercise showing how one unit spans everyday and cosmic magnitudes.
Conversion Formula
To convert hands to astronomical units, multiply by this factor:
Step-by-Step Example
Convert 25 hands to astronomical units.
How to Convert hands to astronomical units
Bridging a horse-height unit to a cosmic one uses one very small factor.
- Take the length in hands: Note the number of hands (each 4 inches).
- Multiply by 6.791541 × 10⁻¹³: This is the au equivalent of one hand.
- Use scientific notation: The answer is tiny, so express it with a power of ten.
- Result: 25 hh × 6.791541 × 10⁻¹³ = 1.697885 × 10⁻¹¹ au.
hands to astronomical units conversion table
| hands (hh) | astronomical units (au) |
|---|---|
| 0 | 0 |
| 1 | 6.791541e-13 |
| 2 | 1.358308e-12 |
| 3 | 2.037462e-12 |
| 4 | 2.716616e-12 |
| 5 | 3.39577e-12 |
| 6 | 4.074924e-12 |
| 7 | 4.754078e-12 |
| 8 | 5.433232e-12 |
| 9 | 6.112386e-12 |
| 10 | 6.791541e-12 |
| 15 | 1.018731e-11 |
| 20 | 1.358308e-11 |
| 25 | 1.697885e-11 |
| 30 | 2.037462e-11 |
| 40 | 2.716616e-11 |
| 50 | 3.39577e-11 |
| 60 | 4.074924e-11 |
| 70 | 4.754078e-11 |
| 80 | 5.433232e-11 |
| 90 | 6.112386e-11 |
| 100 | 6.791541e-11 |
| 150 | 1.018731e-10 |
| 200 | 1.358308e-10 |
| 250 | 1.697885e-10 |
| 300 | 2.037462e-10 |
| 400 | 2.716616e-10 |
| 500 | 3.39577e-10 |
| 600 | 4.074924e-10 |
| 700 | 4.754078e-10 |
| 800 | 5.433232e-10 |
| 900 | 6.112386e-10 |
| 1000 | 6.791541e-10 |
| 2000 | 1.358308e-9 |
| 3000 | 2.037462e-9 |
| 4000 | 2.716616e-9 |
| 5000 | 3.39577e-9 |
| 10000 | 6.791541e-9 |
| 25000 | 1.697885e-8 |
| 50000 | 3.39577e-8 |
| 100000 | 6.791541e-8 |
| 250000 | 1.697885e-7 |
| 500000 | 3.39577e-7 |
| 1000000 | 6.791541e-7 |
What is the Hand?
The hand is a non-SI unit of length used almost exclusively to measure the height of horses and other equines, taken from the withers (the ridge between the shoulder blades) to the ground.
Definition
One hand is defined as exactly 4 inches, or 0.1016 metre.
Heights are conventionally written with the whole number of hands, a decimal point, and the number of remaining inches (0 to 3), so "15.2 hands" means 15 hands plus 2 inches, i.e. 62 inches, not 15.2 hands in a base-ten sense. The abbreviation is often "hh" for "hands high."
Origin and History
The hand derives from the breadth of a human hand and appears among the oldest recorded units, referenced in ancient Egyptian and Babylonian metrology. In England it was standardised by statute of Henry VIII in 1541 to a fixed 4 inches, removing its dependence on the varying size of an actual hand.
Law and Notable Facts
The hand remains the legal and customary unit for equine height in English-speaking countries, including the United States, the United Kingdom, Canada, Australia, and Ireland; most of continental Europe measures horses in centimetres instead. Because a hand is exactly 4 inches, the fractional notation ".1", ".2", and ".3" represents 1, 2, and 3 inches respectively.
Real-World Examples and Conversions
- A horse must generally stand at least 14.2 hands (58 inches, 1.4732 m) to be classed as a horse rather than a pony.
- A typical Thoroughbred racehorse stands about 16 hands (64 inches, 1.6256 m).
- The tallest horses, such as the Shire breed, can exceed 18 hands (72 inches, 1.8288 m).
- 15 hands equals 60 inches, which is exactly 1.524 m.
What is the astronomical unit?
The astronomical unit (au) is a unit of length used in astronomy to express distances within the Solar System, roughly the mean distance between Earth and the Sun.
Definition
The astronomical unit is defined as exactly 149,597,870,700 metres.
Since 2012 this is a fixed conventional value adopted by the International Astronomical Union (IAU), replacing the earlier definition based on the Gaussian gravitational constant. Related astronomical units build on it: 1 light-year ≈ 63,241 au and 1 parsec ≈ 206,265 au.
Origin and History
The concept dates to antiquity as astronomers sought the Earth–Sun distance to scale the Solar System. Early estimates were crude; the 1761 and 1769 transits of Venus allowed the first reasonably accurate measurements. For most of the 20th century the au was defined dynamically via Kepler's third law and the Gaussian constant. In 2012 the IAU redefined it as a fixed number of metres to eliminate its dependence on the changing measured value of the heliocentric gravitational constant.
Law and Notable Facts
The au is accepted for use with the SI, with the symbol "au" recommended by the IAU and BIPM (older texts use "AU" or "ua"). Light travels one astronomical unit in about 499 seconds, or roughly 8.3 minutes—the reason sunlight reaching Earth is always about 8 minutes old.
Real-World Examples and Conversions
- Earth orbits the Sun at 1 au (about 149.6 million km).
- Neptune orbits at roughly 30 au from the Sun.
- The Voyager 1 spacecraft is over 160 au away as of the 2020s.
- 1 au ≈ 92.956 million miles ≈ 499 light-seconds.
Frequently Asked Questions
How many astronomical units is one hand?
One hand equals 6.791541 × 10⁻¹³ astronomical units—an extraordinarily tiny fraction because a hand is 10.16 cm while an au is about 150 million kilometers.
How do I convert astronomical units back to hands?
Multiply the au value by 1,472,420,000,000 (1.47242 × 10¹²). Even a fraction of an au equals an astronomical number of hands.
Why is this conversion so extreme?
The two units differ by roughly twelve orders of magnitude—one is sized for measuring horses, the other for planetary orbits—so the factor is vanishingly small.
What is a hand actually used for?
The hand is the traditional unit for stating a horse's height, measured from the ground to the withers; a 16-hand horse stands 64 inches at the shoulder.
How many hands make up one astronomical unit?
About 1.47 × 10¹² hands, meaning you would need well over a trillion hand-lengths laid end to end to span the Earth-Sun distance.
People also convert
Complete hands conversion table
| Unit | Result |
|---|---|
| Nanometers (nm) | 101600000 nm |
| Micrometers (μm) | 101600 μm |
| Millimeters (mm) | 101.6 mm |
| Centimeters (cm) | 10.16 cm |
| Decimeters (dm) | 1.016 dm |
| Meters (m) | 0.1016 m |
| Kilometers (km) | 0.0001016 km |
| light-years (ly) | 1.073913e-17 ly |
| astronomical units (au) | 6.791541e-13 au |
| parsecs (pc) | 3.292632e-18 pc |
| ångströms (angstrom) | 1016000000 angstrom |
| Mils (mil) | 4000 mil |
| Inches (in) | 4 in |
| Yards (yd) | 0.1111111 yd |
| US Survey Feet (ft-us) | 0.3333327 ft-us |
| Feet (ft) | 0.3333333 ft |
| Fathoms (fathom) | 0.05555556 fathom |
| Miles (mi) | 0.00006313131 mi |
| Nautical Miles (nMi) | 0.00005485961 nMi |
| chains (ch) | 0.005050505 ch |
| rods (rd) | 0.02020202 rd |
| furlongs (fur) | 0.0005050505 fur |