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Multiple conversions
To convert from Gram (g) to Microgram (mcg), use the following formula:
Microgram (mcg)
= 106× Gram (g)
To convert from Gram (g) to Milligram (mg), use the following formula:
Milligram (mg)
= 1000× Gram (g)
To convert from Gram (g) to Kilogram (kg), use the following formula:
Kilogram (kg)
= 11000× Gram (g)
= 0.001× Gram (g)
To convert from Gram (g) to Metric Tonne (mt), use the following formula:
Metric Tonne (mt)
= 1106× Gram (g)
= 10-6× Gram (g)
To convert from Gram (g) to Ounce (oz), use the following formula:
Ounce (oz)
= 1453.59237 × 16× Gram (g)
= 0.035273961949580412916× Gram (g)
With 1453.59237 is the ratio between the base units Pound (lb) and Gram (g).
To convert from Gram (g) to Pound (lb), use the following formula:
Pound (lb)
= 1453.59237× Gram (g)
= 0.0022046226218487758072× Gram (g)
With 1453.59237 is the ratio between the base units Pound (lb) and Gram (g).
To convert from Gram (g) to Stone (st), use the following formula:
Stone (st)
= 1453.59237 × 114× Gram (g)
= 0.00015747304441776970052× Gram (g)
With 1453.59237 is the ratio between the base units Pound (lb) and Gram (g).
To convert from Gram (g) to Ton (t), use the following formula:
Ton (t)
= 1453.59237 × 12000× Gram (g)
= 0.0000011023113109243879036× Gram (g)
With 1453.59237 is the ratio between the base units Pound (lb) and Gram (g).
A gram (g) is a base unit of mass in the metric system. The plural form is grams.
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.
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.
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 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.
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.