What is ounce?
An ounce is a unit of mass in imperial and US customary systems equal to approximately 28.35 grams. It is frequently used in cooking, food portioning, and the measurement of precious metals.
Real-world uses
Ounces are used in the US and UK for food packaging, postal weights, and cooking recipes. Precious metals are weighed in troy ounces (slightly heavier than avoirdupois ounces) on commodity exchanges worldwide.
History
The word "ounce" comes from the Latin "uncia," meaning one-twelfth (of a Roman pound). The avoirdupois ounce became standard in English trade by the 14th century, defined as 1/16 of an avoirdupois pound.
Common mistakes
Confusing avoirdupois ounces (28.35 g, used for general weight) with troy ounces (31.10 g, used for precious metals) or fluid ounces (a volume measure). These are three distinct units sharing the name "ounce."
What is stone?
A stone is a unit of mass used primarily in the United Kingdom and Ireland, equal to 14 pounds. It is mainly used to express human body weight in everyday conversation.
Real-world uses
The stone is used primarily in the UK and Ireland for expressing body weight (e.g., "I weigh 11 stone"). It appears on bathroom scales sold in Britain and is the preferred unit in British medical consultations for patient weight discussions.
History
The stone has been used in the British Isles since at least the 14th century for weighing agricultural goods. Its value varied historically (from 4 to 32 pounds depending on the commodity) before being fixed at 14 pounds by the Weights and Measures Act of 1835.
Common mistakes
Assuming a stone is used outside the British Isles—it is virtually unknown in the US, continental Europe, or most other countries. Also, forgetting that 1 stone = 14 pounds, not 10 or 12.
When is this conversion used?
Cooking recipes and food packaging often switch between grams and ounces, especially when adapting recipes from different culinary traditions.
Worked examples
1 ounce = 0.00446429 stone
1 stone = 6.35029318 kilogram
How to convert ounce to stone
To convert ounce to stone, multiply the value by 0.00446429.
To convert stone back to ounce, multiply by 224.
Measurement standards
The kilogram is defined by fixing the Planck constant to exactly 6.62607015 × 10⁻³⁴ joule-seconds, as established at the 26th General Conference on Weights and Measures in 2018. This ended the last SI definition based on a physical artefact.
Did you know?
The International Prototype of the Kilogram, a platinum-iridium cylinder stored near Paris since 1889, was found to have drifted by about 50 micrograms relative to its copies over a century — roughly the mass of a fingerprint.
Quick reference: ounce to stone
| ounce | stone |
|---|---|
| 0.1 | 0.00044643 |
| 0.5 | 0.00223214 |
| 1 | 0.00446429 |
| 2 | 0.00892857 |
| 5 | 0.02232143 |
| 10 | 0.04464286 |
| 25 | 0.11160714 |
| 50 | 0.22321429 |
| 100 | 0.44642857 |
| 250 | 1.11607143 |
| 500 | 2.23214286 |
| 1,000 | 4.46428571 |
Common values
| ounce | stone | |
|---|---|---|
| A paperclip | 35.27396195 ounce | 0.15747304 stone |
| A smartphone | 6,172.94334118 ounce | 27.55778277 stone |
| A bag of sugar | 35.27396195 ounce | 0.15747304 stone |
| Average adult human | 2,469.17733647 ounce | 11.02311311 stone |
| A small car | 42,328.7543395 ounce | 188.9676533 stone |