How to Convert ounces to grams
Converting ounces to grams is simple. One ounce equals exactly 28.3495 grams. To convert any weight from ounces to grams, multiply the ounce value by 28.3495.
Grams = Ounces × 28.3495
For example, if you want to convert 8 ounces to grams: 8 × 28.3495 = 226.796 grams. Our calculator above handles this automatically with precision up to 2 decimal places.
Worked Examples
Example 1: Convert 3 ounces to grams
3 × 28.3495 = 85.0485 grams
Example 2: Convert 12 ounces to grams
12 × 28.3495 = 340.194 grams
Example 3: Convert 16 ounces to grams
16 × 28.3495 = 453.592 grams (exactly 1 pound)
The Math Behind the Conversion
The conversion factor 28.3495 comes from the international avoirdupois ounce definition. One avoirdupois ounce is defined as exactly 28.349523125 grams. This value was established by the 1959 international yard and pound agreement, which standardized the avoirdupois pound as exactly 0.45359237 kilograms. Since there are 16 ounces in a pound, dividing 453.59237 grams by 16 gives 28.349523125 grams per ounce exactly.
Common Mistakes
- Using 30 grams per ounce: Some people round 28.35 up to 30 for easy mental math, but this creates a 5.8% error. For recipes and commerce, always use 28.3495.
- Confusing fluid ounces with weight ounces: A fluid ounce measures volume. For water, 1 fluid ounce weighs approximately 1 ounce, but for other materials like flour or oil, the weight differs significantly from the volume.
- Forgetting about troy ounces: Precious metals use troy ounces, which equal 31.1035 grams. If you are weighing gold, silver, or gemstones, use the troy ounce conversion, not the avoirdupois conversion.
Common ounces to grams Conversions
| Ounces (oz) | Grams (g) |
|---|---|
| 1 oz | 28.35 g |
| 2 oz | 56.70 g |
| 3 oz | 85.05 g |
| 4 oz | 113.40 g |
| 6 oz | 170.10 g |
| 8 oz | 226.80 g |
| 10 oz | 283.50 g |
| 12 oz | 340.19 g |
| 14 oz | 396.89 g |
| 16 oz | 453.59 g |
| 20 oz | 566.99 g |
| 24 oz | 680.39 g |
| 32 oz | 907.18 g |
| 48 oz | 1360.78 g |
| 64 oz | 1814.37 g |
Quick Reference Chart
Everyday items converted from ounces to grams
| Item | Ounces (oz) | Grams (g) |
|---|---|---|
| Slice of bread | 1.2 oz | 34 g |
| Chicken egg | 1.8 oz | 50 g |
| Butter stick | 4 oz | 113 g |
| Hamburger patty | 4 oz | 113 g |
| Chocolate bar | 1.55 oz | 43 g |
| Bag of chips | 1 oz | 28 g |
| Protein scoop | 1.1 oz | 30 g |
| Postage stamp | 0.035 oz | 1 g |
| Letter (paper) | 0.18 oz | 5 g |
| Baseball | 5.1 oz | 145 g |
| Smartphone | 6.3 oz | 180 g |
| Can of soda | 13 oz | 370 g |
Industry Applications
Ounce to gram conversions are critical in the food and beverage industry. American food packaging, recipes, and nutritional labels use ounces, while international markets require grams. A cereal box containing 12 ounces must show 340 grams for European consumers. Restaurants with international menus must convert portion sizes accurately to maintain consistency across locations.
In health, fitness, and nutrition, protein powders, supplements, and meal plans are often measured in grams for precision but sold in ounces in the US. A fitness coach recommending 30 grams of protein per meal needs to know this equals approximately 1.06 ounces. Bodybuilders tracking macronutrients switch between grams and ounces depending on their food source and measuring tools.
The baby and childcare products industry relies on these conversions for formula preparation, diaper sizing by weight, and baby food portions. International parents buying American formula online must convert ounce-based scoop instructions to grams for their kitchen scales. Similarly, European baby food jars labeled in grams must be converted for US caregivers.
Postal and shipping services calculate rates based on weight, and international shipments require weights in the unit standard of the destination country. USPS uses ounces and pounds, while most international carriers use grams and kilograms. A package weighing 8 ounces must be declared as 226.8 grams for customs forms in metric countries.
Conversion History
The ounce traces its lineage to the Roman uncia, meaning one-twelfth part. Various ounce standards developed across Europe over the centuries. The avoirdupois ounce, used for general weighing today, was formalized in England and became the standard for trade. In 1959, the international yard and pound agreement defined the avoirdupois pound as exactly 0.45359237 kilograms, making the ounce exactly 28.349523125 grams.
The gram was introduced in 1795 as part of the metric system. Defined originally as the weight of one cubic centimeter of water at 4°C, it provided a natural, reproducible standard. The gram became the foundation of the metric weight system, with prefixes like kilo-, milli-, and micro- enabling measurements across vast scales. Today, the gram is used for virtually all scientific, medical, and commercial weighing outside the United States.
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Frequently Asked Questions
How do I convert ounces to grams?
To convert ounces to grams, multiply the weight in ounces by 28.3495. For example, 5 oz × 28.3495 = 141.7475 grams.
What is 1 ounce in grams?
1 ounce is equal to 28.3495 grams. For quick estimates, you can use 28.35 grams per ounce.
How many grams is 8 ounces?
8 ounces is equal to 226.796 grams. Use our converter above for exact calculations.
Is this ounces to grams converter free?
Yes, our ounces to grams converter is completely free to use with no signup required.
How many grams is 16 ounces?
16 ounces is equal to 453.592 grams. This is exactly 1 pound, which is why 16 oz is often called a pound in the US customary system.
How do I convert ounces to grams without a calculator?
For a quick estimate, multiply ounces by 28. For example, 4 oz × 28 = 112 grams (actual: 113.4 grams). For a closer approximation, multiply by 28.35. This works well for cooking and everyday weighing.
What is the difference between ounces and grams?
Ounces are part of the imperial/customary system used primarily in the United States. Grams are part of the metric system used worldwide. One ounce equals 28.3495 grams, and one gram equals 0.035274 ounces. Grams are typically used for precise measurements in science, medicine, and international commerce.
Why do countries use different weight systems?
The United States maintained the British imperial system after independence and never fully adopted the metric system. Most other countries switched to grams and kilograms because the metric system is decimal-based, easier to learn, and standardized for global trade and scientific collaboration.
Is this ounces to grams conversion accurate for baking?
Yes, our converter is accurate to 2 decimal places, which is ideal for baking and cooking. Professional bakers often prefer grams for their precision, as measuring flour by weight in grams produces more consistent results than measuring by volume in cups or ounces.
Can I use this converter for baby formula and feeding?
Yes, you can use this converter for baby formula preparation. However, always follow the specific instructions on your formula packaging, as different brands may have different scoop sizes and mixing ratios. When in doubt, use the measuring system recommended by the manufacturer or your pediatrician.