# Definition:Avoirdupois

## Definition

The avoirdupois system is one of the three imperial systems of measurement of mass.

Its units are defined as follows:

### Grain

The grain is the imperial unit of mass which is used as the basis of all three of the imperial weight systems.

$1$ grain $= \dfrac 1 {437 \cdot 5}$ ounce avoirdupois $\approx 64 \cdotp 8$ milligrams.

### Dram

$1$ dram $= 27 \cdotp 34375$ grains $= \dfrac 1 {16}$ ounce avoirdupois $\approx 1 \cdotp 77$ grams.

### Ounce

$1$ ounce avoirdupois $= 16$ drams $= 437 \cdotp 5$ grains $= 28 \cdotp 34952 \, 3125$ grams.

The gram equivalent is defined to be exact.

### Pound

$1$ pound avoirdupois $= 16$ ounces avoirdupois $= 7 \, 000$ grains $= 453 \cdotp 59237$ grams.

The gram equivalent is defined to be exact.

### Stone

$1$ stone $= 14$ pounds avoirdupois $= 224$ ounces avoirdupois $= 6 \, 350 \cdotp 29318$ grams.

The gram equivalent is exact.

### Quarter

$1$ quarter $= 2$ stone $= 28$ pounds avoirdupois $\approx 12 \cdotp 7$ kilograms.

### Hundredweight

$1$ hundredweight $= 4$ quarters $= 8$ stone $= 112$ pounds avoirdupois $\approx 50 \cdotp 8$ kilograms.

### Ton

 $\displaystyle$  $\displaystyle 1$ ton $\displaystyle$ $=$ $\displaystyle 20$ hundredweight $\displaystyle$ $=$ $\displaystyle 80$ quarters $\displaystyle$ $=$ $\displaystyle 160$ stone $\displaystyle$ $=$ $\displaystyle 2240$ pounds avoirdupois $\displaystyle$ $\approx$ $\displaystyle 1016$ kilograms

## Linguistic Note

The word avoirdupois derives from the Norman French word whose literal translation is goods (that is property, or things owned) of weight.

The avoir part also means to have in modern French, and derives from the Latin habere.

It is pronounced something like av-wah-doo-pwah, although Francophones will be aware that there are further subtleties to this.