A hectogram (hg) is a unit of mass/weight in the International System of Units (SI), the modern form of the metric system of measurement.

1 hectogram = 0.1 kilograms

1 hectogram = 100 grams

Below are some relationships between hectograms and units of mass in the US customary system of measurement.

1 hectogram = 0.22 pounds

1 hectogram = 3.527 ounces

The hectogram is not a widely used unit of mass. This is mostly because it is almost the same size as a kilogram, the SI base unit of mass; there are 10 hectograms in 1 kilogram, so in most cases where a hectogram may be used, a kilogram would be used instead because it is the base unit, and is more widely known. There is little reason to use hectograms over kilograms except in cases where a high level of precision is necessary, or by convention for specific applications. For example, in Italy, the hectogram is a commonly used unit in the food retail industry, whereas the US typically uses grams for this purpose.

SI prefixes

The International System of Units (SI) makes use of SI prefixes (milli-, centi-, kilo-, deca-, etc.) to denote multiples or submultiples of a base unit that are related by a power of 10. The base unit of mass in SI is the kilogram. The kilogram is unique as a base unit in that it is the only base unit that already has an SI prefix, kilo-, indicating that 1 kilogram is 103 grams. All other base units in SI such as meters, seconds, moles, etc., do not have prefixes.

Since SI does not allow for the use of multiple prefixes (e.g. "kilomilligram") to modify a base unit, prefixes are added to the gram, rather than kilogram, to denote different multiples or submultiples of mass.

1 hectogram = 10-1 kilograms

1 hectogram = 102 grams

1 hectogram = 104 centigrams

1 hectogram = 105 milligrams

Remembering SI prefixes and what power of 10 they represent is helpful because it allows us to choose the most appropriate unit for whatever is being measured. For example, a large orange weighs around 1 hectogram (or 100 grams). Measured in milligrams, a 1 hectogram orange has a mass of 100,000 mg. While this value may still be relatively simple to work with when making calculations, it is still more tedious than working with a value of 1 hectogram.

It is also important to be able to convert between various measurements of mass in different systems, particularly from US customary units to SI, since SI is the standard used throughout most of the world.


Convert the following measurements to hectograms and kilograms.

1. 12 pounds.

There are 0.22 pounds in 1 hectogram, or 4.536 hectograms in 1 pound, so:

12 × 4.536 = 54.432 hg

54.432 × 10-1 = 5.443 kg

2. 24 ounces:

There are 0.283 hectograms in 1 ounce, or 3.527 ounces in 1 hectogram, so:

24 ounces × 0.283 = 6.792 hg

6.792 × 10-1 = 0.679 kg