Convert Weight from Ounces to Grams (oz to g)

Ounce to Gram Conversion Formula

Example

Let's convert 5 Ounce (oz) to Gram (g).

Using the formula:

Therefore, 5 Ounce (oz) is equal to 141.747615625 Gram (g).

How many ounces are in one gram? One Gram (g) contains 0.035273961949580412916 Ounces (oz) — the inverse of the factor above. Multiplying by 28.349523125 takes you from ounces to grams; multiplying by 0.035273961949580412916 brings you back.

Put in words: one ounce equals 28.349523125 grams, so the ounce is the larger 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 Gram (g)?

A gram (g) is a base unit of mass in the metric system. The plural form is grams.

Where Did the Gram Originally Come From?

The gram was initially defined in 1795 by the French National Convention.

Its first definition was based on the mass of one cubic centimeter of pure water at the temperature of its maximum density, which is approximately 4 degrees Celsius (4 °C).

This practical, water-based definition was a revolutionary step toward a standardized and universal system of measurement, moving away from the inconsistent and often confusing units of time.

Grams vs. Ounces: What's the Difference?

A gram is much smaller than an ounce, the standard unit of mass in the imperial and US customary systems.

One ounce equals approximately 28.35 grams, which is why grams are preferred for scientific work and for measuring small amounts, such as spices or medicine.

The metric system's decimal structure (for example, 1,000 grams in a kilogram) also makes calculations simpler than in the imperial system.

How Is the Gram Defined Today?

Although the gram was once tied to water, it's no longer linked to any physical object.

Since 2019, the kilogram — and therefore the gram — is defined by a fundamental constant, the Planck constant (h).

That shift makes the unit stable and reproducible in any properly equipped laboratory, without relying on the old International Prototype of the Kilogram.

The Gram's Odd Position in SI

The gram is the unit people use, but it is not the one the system is built on. The kilogram is the SI base unit of mass — the only base unit whose name carries a prefix.

This is a historical accident with practical consequences. Because the base unit already contains "kilo", SI prefixes are stacked on the gram rather than the kilogram: a millionth of a kilogram is a milligram, not a "microkilogram". The rule to remember is that prefixes always attach to gram, so the ladder runs microgram → milligram → gram → kilogram → megagram, where a megagram is what almost everyone calls a tonne.

Grams in Cooking and Nutrition

The gram's dominance in the kitchen comes from a property the imperial system cannot match: it measures mass, not volume.

A cup of flour can vary by 20% depending on whether it was scooped or spooned and how much it has settled; 120 grams of flour is 120 grams every time. This is why baking recipes — where ratios decide whether a dough works — moved to grams long before general cooking did, and why kitchen scales displaced measuring cups in professional practice.

Nutrition labelling relies on the same unit worldwide. Macronutrients are declared in grams per serving or per 100 g, with sodium and micronutrients in milligrams and vitamins often in micrograms. The per-100-gram convention exists specifically so that two products in different package sizes can be compared directly, without arithmetic.

Ounce to Gram Conversion Table

Here are some quick reference conversions from Ounce (oz) to Gram (g):