Convert Weight from Ounces to Stones (oz to st)

Ounce to Stone Conversion Formula

Example

Let's convert 5 Ounce (oz) to Stone (st).

Using the formula:

Therefore, 5 Ounce (oz) is equal to 0.022321428571428571429 Stone (st).

How many ounces are in one stone? One Stone (st) contains 224 Ounces (oz) — the inverse of the factor above. Multiplying by 0.0044642857142857142857 takes you from ounces to stones; multiplying by 224 brings you back.

Put in words: one ounce equals 0.0044642857142857142857 stones, so the ounce is the smaller unit of this pair. Converting between them never changes the amount of weight being measured — only the size of the unit you count it in.

What is an Ounce (oz)?

An ounce (oz) is a unit of mass in the imperial system, equal to 0.0625 (or 1/16) Pounds (lb).

What's the Difference Between a Troy Ounce and a Standard Ounce?

While most people are familiar with the standard ounce used for groceries, there is another crucial measurement called the Troy Ounce.

The standard ounce, officially known as the Avoirdupois ounce, is approximately 28.35 grams and is used for weighing everyday items.

The Troy ounce, however, is slightly heavier, at approximately 31.1 grams, and is the universal standard for measuring precious metals, such as gold, silver, and platinum. This distinction is vital in the jewelry and investment markets.

Ounce vs. Fluid Ounce: Are They the Same?

A common point of confusion is the difference between an ounce (oz) and a fluid ounce (fl oz).

An ounce is a unit of mass (weight), while a fluid ounce is a unit of volume.

For example, you would use ounces to weigh a block of cheese but fluid ounces to measure a glass of milk. The weight of one fluid ounce of a liquid depends entirely on its density; one fluid ounce of honey, for instance, weighs more than one fluid ounce of water.

Where Did the Ounce Come From?

The word "ounce" comes from the Latin uncia.

In ancient Rome, an uncia was one-twelfth of a libra (the Roman pound), and that system helped shape many European measures.

Today's avoirdupois ounce is one-sixteenth of a pound. However, the name still preserves a direct link to Rome's old system of weights and measures.

Three Different Ounces

"Ounce" names three distinct quantities, and mixing them up is the single most common error involving the unit.

• Avoirdupois ounce — the everyday ounce, 28.3495 g, one-sixteenth of a pound. This is what a recipe or a postal scale means.
• Troy ounce — 31.1035 g, used only for precious metals. A gold price quoted "per ounce" is always per troy ounce, which is about 10% heavier than the ordinary one.
• Fluid ounce — not a mass at all, but a volume: about 29.57 mL in the United States and 28.41 mL in the imperial system.

The fluid ounce causes the most trouble because the abbreviations look alike and the numbers are close. Eight ounces of water happens to weigh roughly eight fluid ounces, which makes the confusion survivable for water and badly wrong for flour, honey or oil.

What is a Stone (st)?

The stone (st) is a unit of measurement equal to 14 pounds (lb).

It's part of the imperial system and is still commonly used in a few countries, especially for weighing people.

How Many Kilograms are in a Stone?

For use in international contexts or scientific applications, the stone is often converted to the metric system.

One stone is equal to exactly 6.35029318 kilograms (kg).

This precise conversion is used in international trade and science to ensure everyone is using the exact standard measurement.

Why is Body Weight Measured in Stone?

Although it's an older unit, the stone remains the primary unit of measurement for body weight in the United Kingdom and Ireland.

It's common to hear someone state their weight as a combination of stone and pounds, like "12 stone 6 pounds."

Where Did the Stone Unit Come From?

The stone traces its origins back to the medieval English wool trade, where a "stone of wool" referred to a standard 14-pound measure used for buying and selling.

Stones for other goods could vary in weight—for example, a stone of glass was just 5 pounds—but over time, the 14-pound stone became the official legal standard.

How the Stone Is Actually Written

The stone is almost never used on its own. Body weight in Britain and Ireland is quoted as stones and pounds, with the remainder written out rather than expressed as a decimal.

A person weighing 72 kg is "11 stone 4" — that is 11 st 4 lb, or 158 pounds — not "11.3 stone". Reading the decimal form as pounds is a common error: 11.3 st is 11 st 4.2 lb, close by coincidence, but 11.5 st means 11 st 7 lb, not 11 st 5 lb.

The conversions worth keeping to hand are:

• 1 stone = 14 pounds = 6.35029 kilograms
• 1 kilogram ≈ 0.157473 stone
• A useful mental check: 10 stone ≈ 63.5 kg, and each additional stone adds a little over 6 kg.

Where the Stone Is and Is Not Used

The unit's survival is unusually specific. It was removed from British trade use by weights and measures legislation, so nothing is sold by the stone — shop scales read in kilograms and grams.

What survives is personal and conversational use: body weight, and by extension the weight of livestock and sporting figures such as boxing and horse-racing weights. Medical records in the UK are kept in kilograms, but patients are routinely told their weight in stones and pounds because that is the number they recognise.

Outside Britain and Ireland the unit is essentially unknown. The United States, despite sharing the pound, does not use the stone at all — American body weight is quoted in pounds alone, which is why a US figure of "158 lb" and a UK figure of "11 st 4" describe exactly the same person.

Ounce to Stone Conversion Table

Here are some quick reference conversions from Ounce (oz) to Stone (st):