How many kJ are in 1g of sugar? Conversion and Nutritional Facts

December 28, 2025 •

3 min read

Typically, one gram of sugar provides approximately 17 kJ of energy. This is the standard conversion factor utilized by health organizations and food producers.

Quick Summary

One gram of sugar contains roughly 17 kilojoules of energy, consistent with all carbohydrates. This energy value helps users interpret food labels and make informed choices. The distinction between kilojoules and kilocalories is crucial.

Key Points

Standard Conversion: 1 gram of sugar provides approximately 17 kilojoules (kJ) of energy, the same as other carbohydrates.
KJ vs. Kcal: 17 kJ is equivalent to roughly 4 kilocalories (kcal), a different unit of energy measurement often used in the US.
Different Sugars: While the specific kJ per gram varies slightly between sucrose (table sugar) and glucose, the standard 17 kJ/g is the accepted average for all digestible carbohydrates.
Food Label Interpretation: Use the 17 kJ/g figure to estimate the energy from sugar based on nutritional information panels.
Energy Source Comparison: Per gram, sugar provides less energy than fat (37 kJ) but the same as protein (17 kJ), highlighting the importance of looking at overall diet.
Balanced Diet: Excessive intake of high-sugar foods can contribute to a high energy intake and displace more nutrient-dense foods, emphasizing the importance of moderation.

Understanding the Energy in 1g of Sugar

For those monitoring their diet, the energy content of food is important. Sugar, a type of carbohydrate, provides energy consistent with other carbs. The standard figure is 17 kilojoules (kJ) per gram. This is used in food labeling, especially in Australia and New Zealand, where kilojoules are the standard unit of measurement.

Kilojoules vs. Calories

Confusion often arises when discussing food energy and the difference between kilojoules (kJ) and kilocalories (kcal), often called 'calories'. While both are units of energy, they represent different values. One kilocalorie is equal to approximately 4.184 kilojoules. So, the 17 kJ per gram of sugar translates to about 4 kcal per gram.

Kilojoules (kJ): The standard International System of Units (SI) measure for energy. Used on food labels in many countries globally.
Kilocalories (kcal) or Calories (Cal): The unit of energy commonly used in the United States and some other regions. One large 'Calorie' is the same as one kilocalorie.

The Source of Sugar's Energy

All carbohydrates, including sugar, provide energy through metabolism. Sugar is broken down into glucose, which the body uses for fuel. This provides a quick energy burst. This process is essential, but excess intake can lead to health concerns, as the body converts surplus energy into fat for storage.

Different Types of Sugar and Their kJ Content

While the general rule is 17 kJ per gram, there are minor variations between different types of sugars, such as glucose and sucrose, but for general nutritional purposes, they are considered the same.

Sucrose: Table sugar, sucrose consists of glucose and fructose. Its energy value is approximately 16.48 kJ per gram.
Glucose: The body's primary fuel source, glucose has an energy value of about 15.57 kJ per gram.
Starch: A complex carbohydrate, starch has a slightly higher energy density at around 17.48 kJ per gram.

These differences are relatively small and do not significantly impact daily calculations for most people. For practical purposes, using the standard 17 kJ/g for all sugars and available carbohydrates is accurate enough.

How to Calculate Kilojoules from a Food Label

Food labels make it easy to figure out how many kilojoules are in a product. Here's how:

Locate the 'Carbohydrates' section: Find the nutrition information panel on the food packaging.
Find 'Sugars': Look for the value listed under 'Sugars' within the carbohydrates section. Note that this often includes naturally occurring sugars as well as added sugars.
Multiply by 17: Multiply the number of grams of sugar by 17 to get the approximate kilojoule content from sugar.
Consider total carbs: For a more complete picture, you can use the total carbohydrate amount and multiply by 17 kJ/g, as this is the standard conversion for all available carbohydrates.

Comparison of Energy Sources (Table)

To put sugar's energy content into perspective, here's a comparison with other major macronutrients per gram:


Macronutrient	Kilojoules (kJ) per Gram	Kilocalories (kcal) per Gram
Carbohydrates (including sugar)	~17 kJ	~4 kcal
Protein	~17 kJ	~4 kcal
Fat	~37 kJ	~9 kcal
Alcohol	~29 kJ	~7 kcal

As the table shows, fat provides more than double the energy of sugar per gram, while protein provides the same amount. This is why focusing solely on sugar intake without considering the overall energy density of foods, particularly fat content, can be misleading for weight management.

The Role of Sugar in Your Diet

Sugar has a place in a balanced diet. It provides fuel, especially for the brain and muscles. However, excessive intake of added sugars can lead to health problems. This is particularly true for 'empty calories' from foods and drinks that are high in sugar but offer little to no other nutritional benefit.

Excess energy: Too many kilojoules, regardless of source, can lead to weight gain.
Nutrient displacement: High sugar intake can displace more nutrient-dense foods from the diet.
Health impact: Limiting added sugars is a key dietary recommendation to reduce the risk of chronic diseases.

Conclusion

In summary, 1g of sugar contains approximately 17 kilojoules of energy. This is a consistent and fundamental piece of nutritional information that helps in understanding and interpreting food labels. While the exact value varies slightly between different sugar types, the 17 kJ/g figure is the standard benchmark for all digestible carbohydrates. By understanding this conversion, individuals can make more informed choices about their dietary intake and manage their overall energy consumption, balancing their health goals with their food choices. This information is a building block for interpreting broader nutritional guidelines and making healthier decisions. For more detailed nutritional breakdowns and guidelines, you can consult authoritative sources like the Food Standards Australia New Zealand website.

Frequently Asked Questions

One gram of sugar contains approximately 17 kilojoules (kJ) of energy. This figure is the standard energy value for all digestible carbohydrates, including starches and different types of sugars.

No, 17 kJ is a relatively small amount of energy on its own. For context, the average adult daily energy requirement is around 8,700 kJ. Therefore, the kilojoules from one gram of sugar represent only a fraction of a person's total daily energy needs.

Kilojoules and calories are different units for measuring energy. To convert kilojoules to calories, you can use the conversion factor 1 kcal = 4.184 kJ. The 17 kJ in 1g of sugar is equivalent to about 4 kilocalories.

For all practical purposes, yes. While there are minor differences due to trace mineral content, both brown and white sugar provide a similar amount of energy per gram. Standard nutritional guidelines assign them the same value of around 17 kJ/g.

The chemical structure of fat is more energy-dense than that of sugar or other carbohydrates. Fat molecules contain more carbon and hydrogen atoms in proportion to oxygen, allowing them to release more energy when metabolized, yielding 37 kJ per gram compared to 17 kJ for sugar.

The term 'empty calories' is often used for high-sugar foods that provide energy but lack other essential nutrients like vitamins and minerals. While sugar itself provides energy, whether its kilojoules are 'empty' depends on the overall food product it is in. For example, sugar in fruit comes with fiber and vitamins, unlike added sugar in a soft drink.

To reduce sugar intake, and thus the related kilojoules, focus on cutting back on added sugars in sodas, sweets, and processed snacks. Opt for whole foods like fruits and vegetables, which provide naturally occurring sugars along with fiber and other nutrients.