Are there 28 grams in 1 oz?

This is a common question for those working with weights and measures, especially in cooking and baking where precise measurements are important. The quick answer is yes, there are approximately 28 grams in 1 ounce based on the metric and imperial systems of measurement.

Metric System

The metric system is the standard system of measurement used in most of the world. In the metric system, weight is measured in grams and kilograms. One gram is the basic unit of mass in the metric system. One kilogram equals 1000 grams. The gram was officially adopted as a standard unit of mass by the French National Convention in 1795.

The key thing to know is that in the metric system, units of weight are standardized based on multiples of 10. This makes conversions easy to remember and calculate.

Imperial System

The imperial system is the traditional system of measurement used in the United States and some other countries. It is also known as the US customary system or the British Imperial System. In the imperial system, weight is measured in ounces and pounds. One ounce equals 28.35 grams.

The ounce as a unit of weight is widely used in the United States and the United Kingdom, especially for food items like meat, produce, and cooking ingredients. It is important to note that while the ounce is a unit of weight in the imperial system, fluid ounces are a unit of volume.

The imperial system uses more complex conversion factors than the metric system. An important relationship to remember is that 16 ounces make 1 pound. So if 1 ounce equals 28.35 grams, 16 ounces would equal 453.59 grams, which is very close to 1 pound.

The 28 Gram Approximation

Even though an ounce is officially defined as 28.35 grams, it is very common to approximate 1 ounce as equal to 28 grams. This makes calculations and conversions easier without sacrificing much accuracy for most practical purposes.

The 28 gram approximation has likely become popular because 28 is a round number and easier to remember than 28.35. The difference of 0.35 grams is negligible in most non-scientific applications. So for cooking, baking, nutrition tracking, and other everyday uses, 28 grams per 1 ounce is an appropriate and convenient approximation.

Why Accuracy Matters

While 28 grams is close enough for most needs, there are some situations where precision is important. For example:

  • Laboratory and scientific contexts
  • Pharmaceutical applications
  • High-precision manufacturing
  • Jewelry making
  • Some culinary applications

When precision matters, it’s important not to round off and use the official conversion rate of 28.35 grams per ounce. But for most casual everyday uses, 28 grams is an acceptable substitute.


So in summary, the quick answers are:

  • There are officially 28.35 grams in 1 ounce
  • It is common to approximate 1 ounce as 28 grams
  • The 28 gram approximation works for most everyday purposes
  • In contexts where precision matters, 28.35 grams should be used

Knowing both the precise official conversion and the convenient approximation gives you flexibility depending on the context and level of accuracy needed.

Visual Summary

System Unit Conversion
Metric 1 gram Basic unit of mass
Imperial 1 ounce 28.35 grams
Approximation 1 ounce 28 grams

This table provides a quick visual summary of the key units and conversions discussed:

  • In the metric system, the gram is the basic unit
  • In the imperial system, 1 ounce officially equals 28.35 grams
  • But 1 ounce is commonly approximated as 28 grams

Using the 28 Gram Approximation

The 28 gram per ounce approximation can be handy for quick mental math and rough conversions. Here are some examples:


A recipe calls for 4 ounces of flour. Instead of getting out a scale and measuring 28.35 grams, you can approximate and round up to 112 grams (4 * 28 grams). This math is easier to do mentally.

Nutrition Tracking

You eat a 2 ounce bag of nuts. Instead of looking up that 2 ounces equals 56.7 grams, you can record it as 56 grams (2 * 28 grams). Close enough for tracking calories and nutrients.

Postal Shipping

A package weighs 1.5 ounces. Rounding up to 42 grams (1.5 * 28 grams) gives you enough postage without having to look up the precise conversion.

These examples demonstrate how the 28 gram rule of thumb can simplify measurements in everyday situations without losing practical accuracy.

Exceptions to the 28 Gram Rule

While the 28 gram approximation works most of the time, there are some cases where more precision is required:

Lab Research

When a chemistry experiment calls for a precise quantity like 23 ounces of a solution, the full conversion to 653.45 grams would be needed for accurate measurements.

Pharmacy Dispensing

Pharmacists filling prescriptions should use the official 28.35 grams per ounce conversion to ensure patients get the exact prescribed drug dosage.

Jewelry Crafting

A jeweler weighing gems and precious metals would need to use jeweler’s scales with 0.01 gram accuracy instead of rounding to the gram.

For critical applications like these, the 28 gram approximation is not sufficient – accuracy matters.

Converting Between Grams and Ounces

Because the gram and the ounce are different units, you need to know the conversion factor to convert between them. Here are some examples:

Grams to Ounces

To convert grams to ounces, divide the number of grams by 28.35. For example:

115 grams / 28.35 grams per ounce = 4.06 ounces

As a shortcut, you can divide by 28 instead:

115 grams / 28 grams per ounce = 4.11 ounces (close enough)

Ounces to Grams

To convert ounces to grams, multiply the number of ounces by 28.35. For example:

5 ounces x 28.35 grams per ounce = 141.75 grams

As a shortcut, you can multiply by 28 instead:

5 ounces x 28 grams per ounce = 140 grams (close enough)

So if you need to interconvert between grams and ounces, remembering that 1 ounce is approximately 28 grams makes the math easy in your head.

Grams to Ounces Converter

Here is a handy ounces to grams and grams to ounces converter chart:

Ounces Grams
1 28
2 56
3 84
4 112
5 140
6 168
7 196
8 224
9 252
10 280

This conversions table can help you quickly convert between ounces and grams in both directions using the 28 grams per ounce approximation.

Pros and Cons of the 28 Gram Approximation

Here is a summary of the key pros and cons of using the 28 gram per ounce approximation:


  • It’s easy to remember that 1 ounce is 28 grams
  • Mental math and conversions are faster with a round number
  • The small 0.35 gram difference is insignificant for most everyday uses
  • You don’t need to look up or memorize the official 28.35 gram figure


  • It’s not the officially correct conversion rate
  • Rounding introduces a small margin of error
  • The approximation is not suitable for scientific contexts requiring precision

Whether the pros of simplicity and convenience outweigh the cons of reduced accuracy depends on your specific needs and application.

Should the 28 Gram Approximation Be Official?

Some people argue that since 28 grams is so commonly used and works well for most everyday purposes, it should be adopted as the official definition of an ounce. Here are some arguments on both sides of this debate:

Arguments for Making 28 Grams Official

  • It would align with widespread existing practice
  • Calculations would be cleaner and easier
  • It would eliminate confusion from having two numbers
  • The imperial system already has messy conversions

Arguments Against Change

  • Would disrupt existing systems built on current definitions
  • Loss of precision could impact scientific work
  • Changing standards creates headaches transitioning
  • The status quo works fine as is

Overall, there are reasonable points on both sides of this debate. Any change to standardized measurements requires broad consensus and consideration of backwards compatibility. But the ubiquity of the 28 gram approximation will likely continue leading to gradual adoption in more and more everyday contexts.

The Bottom Line

At the end of the day, whether you need the precision of 28.35 grams per ounce or the convenience of 28 grams depends on your specific application and accuracy requirements.

For casual cooking, nutrition tracking, and most household uses, 28 grams per ounce is an easy, handy rule of thumb. But any application where small differences in weight make a critical impact should reference the official conversion rate.

So in summary:

  • 28.35 grams = 1 ounce officially
  • 28 grams ≈ 1 ounce in practice
  • Use 28 when rough is fine
  • Use 28.35 when precision matters

Armed with this knowledge, you can navigate ounces and grams confidently and accurately for any situation!

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