A hand (or handbreadth) is a unit of measurement of length equal to 101.6 millimetres (4 in).
It was originally based on the breadth of a male human hand, and is now standardized at 101.6 millimetres (4 in). When used to measure height, it is abbreviated "h" (for "hands") or "hh" ("hands high").
Use in measuring horses and other equines
Today the hand is primarily used to describe the height of horses, ponies, and other equines in a number of different countries, including the USA, Canada, Australia, and the UK. In this context, one hand equals four inches (10.16 cm), and the horse is measured from the ground to the top of the withers.  So a horse that is 15 hands high (abbreviated 15 hh) is 60 inches (152 cm) from the ground to the top of the withers. Instead of decimal or vulgar fractions, a hand comprises four inch-long steps, so a horse 62 inches (157 cm) tall would be 15.2 hh (spoken as “fifteen two hands high”). An animal between inch increments may be measured by fractions, for example, a very tall pony might be 14.1-3/4 hh (57.75 inches (146.7 cm)).
A pony is generally defined as a horse less than 14.2 hands (58 inches, 147 cm) or, depending on organization, 14.2 hh or less. An animal 14.2 hh or taller is classified as a horse. However, breed characteristics also play a role in defining animals as horses or ponies, particularly in breeds that may have some purebred representatives on both sides of the 14.2 divide. In some nations, such as Australia, the cutoff is defined at 14.0 hands (56 inches, 142 cm)
- Small Pony: 12.2 hands (50 inches, 127 cm) or smaller
- Medium Pony: larger than 12.2 hh, up to 13.2 hands (54 inches, 137 cm)
- Large Pony: larger than 13.2 hh, but no taller than 14.2 hh
A miniature horse is either shorter than 9.2 or 8.2 hh, depending on the registry. Minis often are measured at the last hair of the mane, located approximately at the peak of the withers which are sometimes poorly-defined in minis. The world's smallest horse, Thumbelina, is just 4.1 hh.
In international competition and in much of continental Europe, horses are measured in centimeters instead of hands.
For Fédération Equestre Internationale (FEI) competition and for USEF competition in the USA, a horse can be measured with shoes on or off. In the United Kingdom much official measurement of horses is overseen by the Joint Measurement Board (JMB). For JMB purposes, the shoes must be removed before measurement.
- anthropic units
- Pony, includes discussion of when height alone may not define an animal as a horse or a pony.
- List of horse breeds, includes a discussion of the differences between horses and ponies