Convert Hand (hand) to Petameter (Pm) instantly.
About these units
Hand (hand)
The hand is a traditional unit of length equal to 4 inches, historically used to measure the height of horses. Its origins go back thousands of years, when people commonly relied on body-based measurements. While early hands varied from culture to culture, the modern standardized hand—set at exactly 4 inches—was adopted to bring uniformity to equine measurement worldwide. When measuring a horse, the height is taken at the withers, the ridge between the shoulder blades, because this location provides a stable and consistent point unaffected by head movement. Horse heights are often written in a mixed-unit style: for example, "15.3 hands" means 15 hands plus 3 inches, not 15.3 × 4 inches. Though rarely used outside the world of horsemanship, the hand has become deeply embedded in equestrian culture. It provides a system that is intuitive, easy to visualize, and respectful of longstanding tradition. In modern times, even highly scientific equine breeding and veterinary studies continue to quote measurements in hands.
Petameter (Pm)
A petameter is 10¹⁵ meters and begins bridging the gap between solar system scales and the nearest stars. Distances between stars, the size of large cosmic structures, or the wavelengths of extremely low-frequency electromagnetic waves may be expressed in petameters. For example, a light-year is about 9.46 petameters. Petameters rarely appear in everyday astronomical writing because traditional units like light years and parsecs are more intuitive to astronomers and the public. However, the unit's alignment with SI conventions makes it essential in scientific computation and large-scale modeling, especially when dealing with cosmic distances while maintaining strictly metric consistency.