If you make beer, mead, wine, or cider at home, you will eventually hear the term final gravity, or FG.

Final gravity is the specific gravity of your fermented beverage after fermentation is complete.vIt is one of the most useful measurements in homebrewing.

Final gravity can help you determine:

• If fermentation is complete.
• How much sugar the yeast consumed.
• The approximate alcohol content.
• How dry or sweet the beverage may be.
• If your batch is ready for packaging.

You do not need expensive equipment to measure it. A hydrometer is usually all you need.

What Does Final Gravity Mean?

Specific gravity compares the density of a liquid with the density of water.

Water has a specific gravity of approximately 1.000. Fermenting liquid starts with dissolved sugars and other materials. These materials make the liquid denser than water.

During fermentation, yeast consumes fermentable sugars. The yeast produces alcohol and carbon dioxide. The liquid becomes less dense.

The specific gravity therefore decreases. The gravity at the end of fermentation is called final gravity.

Final Gravity vs. Original Gravity

Final gravity works together with original gravity, or OG.

Original gravity is the gravity before fermentation.

Final gravity is the gravity after fermentation.

For example:

• OG: 1.050
• FG: 1.010

The difference between the two readings shows that fermentation occurred. You can use the two numbers to estimate alcohol content.

Why Is Final Gravity Important?

Final gravity tells you what happened during fermentation.

It can help you determine if the yeast has finished its work. It can also help you understand the finished beverage.

For example, a beer that finishes at 1.008 will usually have a different body and sweetness from a beer that finishes at 1.020. However, final gravity does not tell you everything about flavor. Ingredients, yeast strain, acidity, carbonation, and other factors also matter.

How Do I Measure Final Gravity?

The simplest method is to use a hydrometer.

Take a sample from the fermenter.

Put the sample into a sanitized hydrometer test jar.

Place the hydrometer into the sample.

Let it float freely.

Read the scale at the surface of the liquid.

Record the result.

Check the sample temperature and apply a temperature correction if necessary.

When Should I Take a Final Gravity Reading?

Take the reading after fermentation appears to be complete. Do not decide that fermentation is finished because the airlock has stopped bubbling. A quiet airlock does not prove that fermentation has stopped.

Instead, take a hydrometer reading. Then take another reading days later.

If the readings remain the same, fermentation is likely complete.

How Many Final Gravity Readings Do I Need?

At least two readings are useful.

For example:

Day 1: 1.010

Day 3: 1.010

The stable readings indicate that gravity is no longer changing.

The exact amount of time between readings depends on the beverage and fermentation.

A very active fermentation may change quickly. A slow fermentation may require more time. The important point is that the gravity is stable.

What If My Final Gravity Is Still Changing?

If the gravity is still decreasing, fermentation is still active. Do not package the beverage yet if it will be sealed in a bottle. More fermentation can create more carbon dioxide. In a sealed bottle, this can create excessive pressure.

Wait and take another gravity reading.

What Is a Normal Final Gravity?

There is no single normal final gravity.

Different beverages and recipes can finish at very different gravities.

For example, a dry beer might finish near: 1.005–1.010

A beer with more residual sugars may finish higher.

A dry mead can finish near or below: 1.000

A sweet mead can finish considerably higher.

Wine and cider can also have a wide range of final gravities.

The recipe and fermentation process matter more than a single target number.

Does Final Gravity Tell Me If My Beer Is Sweet?

It can provide a clue. A higher final gravity generally means that more dissolved material remains in the beverage.

This can contribute to:

• Sweetness.
• Body.
• Fullness.
• Texture.

However, final gravity is not a direct sweetness measurement. Not everything left in the beverage is sugar. Different sugars and other compounds also affect flavor. A beer with a high final gravity may not necessarily taste sweet.

What Does a Low Final Gravity Mean?

A low final gravity usually means that yeast consumed a large amount of fermentable sugar. This can result in a drier beverage.

For example, a beer that starts at 1.050 and finishes at 1.006 has fermented a significant amount of its starting sugar.

A dry mead may also finish near 1.000.

However, low final gravity does not automatically mean that the beverage will taste good. Fermentation temperature, yeast strain, ingredients, and other factors also affect the result.

Can Final Gravity Be Below 1.000?

Yes. Some fermented beverages can have a final gravity below 1.000.

Alcohol is less dense than water. A beverage with enough alcohol and very little residual sugar can therefore have a specific gravity below 1.000.

Dry wine and mead can sometimes show readings below 1.000. Do not assume that a reading below 1.000 means that your hydrometer is broken. Check the hydrometer and the fermentation conditions if the result seems unusual.

What Does a High Final Gravity Mean?

A high final gravity means that more dissolved material remains after fermentation.

This can be normal. For example, some beer styles are designed to finish at a higher gravity. A high final gravity can also mean that fermentation has stopped before the yeast consumed all of the fermentable sugar. If the gravity is much higher than expected, investigate the fermentation.

Possible causes include:

• Low fermentation temperature.
• Poor yeast health.
• High starting gravity.
• Insufficient nutrients.
• Yeast alcohol tolerance.
• Low pH.
• Low yeast pitch.
• A less fermentable recipe.

Is a High Final Gravity Always a Stuck Fermentation?

No. This is an important distinction.

A beer can have a high final gravity and still be completely finished. Some recipes contain more unfermentable sugars. These sugars remain after the yeast has finished. The recipe may intentionally produce a full-bodied beer.

Compare your result with the expected final gravity for your recipe. Then use stable hydrometer readings to determine whether fermentation is still active.

What If My Final Gravity Is Higher Than the Recipe?

Do not panic.

A recipe’s expected final gravity is an estimate. Your actual result can vary. Different yeast strains can produce different final gravities.

Your mash temperature, ingredients, fermentation temperature, yeast health, and other factors can also change the result. If the gravity is stable, the fermentation may simply have finished at a different point than expected.

What If My Final Gravity Is Much Higher Than Expected?

A large difference deserves investigation.

First, take another hydrometer reading. Make sure the hydrometer is clean and undamaged. Check the temperature.

Then review your fermentation conditions.

Ask:

• Was the yeast temperature too low?
• Was the original gravity very high?
• Was enough healthy yeast pitched?
• Did the yeast have enough nutrients?
• Has the yeast reached its alcohol tolerance?
• Is the recipe highly dextrinous or otherwise low in fermentability?

These questions can help identify a slow or stuck fermentation.

What If My Final Gravity Is Lower Than Expected?

A lower final gravity can also happen.

The yeast may have fermented more of the available sugar than expected.

This can occur because of:

• A highly attenuative yeast strain.
• A lower mash temperature.
• A highly fermentable wort.
• Different ingredients.
• A fermentation temperature that favored high attenuation.

A lower FG is not automatically a problem. It can simply produce a drier beverage than expected.

What Is Attenuation?

Attenuation describes how much of the extract in wort was fermented by yeast.

A common apparent attenuation calculation is:

Attenuation = (OG − FG) ÷ (OG − 1.000) × 100

For example:

• OG = 1.050
• FG = 1.010

The calculation gives approximately:

80% apparent attenuation

This means the yeast reduced the specific gravity by about 80% of the difference between the original gravity and water. Yeast manufacturers often publish an expected attenuation range for their strains.

How Does Final Gravity Affect Alcohol?

OG and FG work together to estimate alcohol.

A common homebrewing formula is:

ABV ≈ (OG − FG) × 131.25

For example:

• OG = 1.050
• FG = 1.010

The estimated alcohol content is about:

5.3% ABV

This is an estimate. The actual alcohol content can differ.

Why Does Lower FG Usually Mean More Alcohol?

Suppose two batches have the same OG.

Batch A finishes at 1.010.

Batch B finishes at 1.020.

Batch A fermented more of the original material.

It therefore produced more alcohol.

This is why the difference between OG and FG matters. A higher FG usually means that less fermentation occurred.

Can I Use a Refractometer to Measure Final Gravity?

Yes, but it is more complicated. A refractometer works very well before fermentation. After fermentation begins, alcohol affects the reading.

You cannot simply read the Brix scale and treat it as the final gravity. You need to use a correction formula. The calculation normally requires the original gravity and the current refractometer reading.

For beginners, a hydrometer is usually easier.

Is a Hydrometer Better for Final Gravity?

For most homebrewers, yes.

A hydrometer directly measures specific gravity. Alcohol does not require the same type of correction used with a refractometer. You still need to account for temperature.

A hydrometer also gives you a simple way to compare readings over time. This makes it especially useful for deciding when fermentation is complete.

Does Temperature Affect Final Gravity?

Yes. Hydrometers are calibrated for a specific temperature. The temperature may be printed on the hydrometer.

If your sample is warmer or colder, the reading may need correction. For accurate measurements, check the hydrometer instructions. Use a temperature correction table or brewing calculator when needed.

Can I Measure Final Gravity With a Tilt Hydrometer?

Yes. A digital floating hydrometer can monitor gravity inside the fermenter. These devices can send readings to a phone, computer, or other receiver.

They can be very convenient. You can monitor gravity without repeatedly removing samples. However, they cost more than a traditional glass hydrometer.

A basic hydrometer remains an excellent choice for beginners.

Do I Need a Final Gravity Reading Before Bottling?

Yes. This is especially important for bottles that will be naturally carbonated.

If fermentation continues after bottling, yeast can produce additional carbon dioxide. The pressure can become too high. This can cause bottles to leak, break, or burst. Do not use the airlock as your only indication that fermentation is finished. Confirm that gravity is stable.

What If I Want Sweet Beer, Mead, Wine, or Cider?

A high final gravity can be intentional.

For example, you may want a sweet mead. You may also want a beer with more body.

However, you need to control the remaining fermentable sugar. If live yeast remains and fermentable sugar is present, fermentation can restart. This is especially important before bottling.

Sweet beverages often require additional stabilization or a controlled fermentation process.

Can I Add Sugar After Measuring Final Gravity?

Yes, but be careful. Adding fermentable sugar can restart fermentation. This is different from measuring final gravity.

If you add sugar after fermentation, you need to know what the sugar will do. For naturally carbonated beer, measured amounts of priming sugar are intentionally added to create carbonation. For sweet wine or mead, adding sugar without a suitable stabilization or filtration process can cause renewed fermentation.

What If My Gravity Is 1.000?

A reading of 1.000 means that the sample has approximately the same density as water. This does not mean that the beverage contains no alcohol. Alcohol is less dense than water.

A fermented beverage can have significant alcohol even when its gravity is near 1.000. Dry wine, mead, and some ciders can finish near this level.

What If My Gravity Is Below 1.000?

That can also be normal. A sufficiently dry fermented beverage can have a gravity below 1.000. This is particularly common with dry wine and mead.

The exact result depends on alcohol content and the remaining dissolved material. If the reading is far outside what you expect, verify the measurement.

Can I Taste the Sample?

Yes. A hydrometer sample does not need to be wasted.

Tasting the sample can tell you:

• How sweet the beverage is.
• How dry it is.
• Whether alcohol is noticeable.
• Whether acidity is balanced.
• Whether fermentation flavors are present.

Do not return the sample to the fermenter, unless you’re confident in your sanitizing practices. The sample has been exposed to air and equipment. Many brewers will drink it or discard it.

Should I Leave the Beverage in Primary Until Final Gravity?

Often, yes. Many homebrewers leave beer in the primary fermenter until fermentation is complete. There is usually no need to transfer it simply because the airlock has slowed.

The same basic principle can apply to mead, wine, and cider. The correct timing depends on the recipe and aging process.

If you plan to transfer to a secondary vessel, use stable gravity readings to help determine the timing.

What If Final Gravity Changes After I Think Fermentation Is Finished?

Take another reading. If the gravity decreases, fermentation was not complete. This is one reason to avoid rushing to package.

A small change can happen because of measurement differences. A significant change indicates that fermentation is still occurring.

Wait until the gravity is stable.

What If My Final Gravity Never Reaches the Expected Number?

Do not keep waiting forever based on a recipe’s target.

Your fermentation may simply have a different final gravity. If the gravity is stable and the beverage tastes appropriate, the fermentation may be finished. If the gravity is much higher than expected, investigate before packaging.

A stable gravity is more important than reaching an arbitrary number.

The Bottom Line

Final gravity is the specific gravity of your fermented beverage after fermentation is complete.

It is one of the most useful measurements in homebrewing.

Measure it with a hydrometer. Take more than one reading to confirm that the gravity is stable. Use final gravity together with original gravity to estimate alcohol content.

A lower final gravity usually means a drier beverage and more fermentation. A higher final gravity can mean more residual material, but it does not automatically mean that fermentation is stuck.

Most importantly, do not bottle based on a quiet airlock alone. Use stable gravity readings to confirm that fermentation is complete.

Once you understand original gravity and final gravity, you have a much better way to understand what your yeast is doing.

OG tells you where fermentation started. FG tells you where it finished.