Skip to content 
If you have eggs in your refrigerator and aren’t sure how fresh they are, the egg float test gives you a quick place to start.
All you need is a bowl of plain water and an egg. Put the egg in the water and watch what it does. It may sink and lie flat, stand upright on the bottom, or rise toward the surface.
I like the simplicity of this test, but I would not use it as a final answer about food safety. The position of the egg mainly gives you a clue about its age and freshness. Other factors, such as storage and signs of spoilage, still matter.
What Is the Egg Float Test?
The egg float test is a simple water test used to estimate how fresh an egg is.
As an egg ages, its internal air cell becomes larger. That changes its density and makes the egg more buoyant. Eventually, an older egg may stand upright or float in water.
The basic idea is easy:
Egg lies flat → generally fresher
Egg stands upright → older
Egg floats → older still
But I would avoid treating these results as a strict good-or-bad scale.
How to Perform an Egg Float Test
You don’t need special equipment.
What You Need
- One egg
- A clean bowl or glass
- Plain water
The container needs to be deep enough for the egg to become fully covered.
Follow These Steps
- Fill the bowl with enough plain water to cover the egg.
- Gently place the egg into the water.
- Let it settle naturally.
- Look at the position of the egg.
- Compare the result with the three common positions below.
That’s it.
I recommend using plain water rather than adding salt or other ingredients. Changing the water’s density can affect the result.
How to Read the Egg Float Test
The egg’s position in the water can tell you quite a bit about its age.
1. The Egg Lies Flat on the Bottom
If the egg sinks and rests horizontally on the bottom, it is generally a fresher egg.
Fresh eggs have a smaller air cell, so they are denser and tend to sink.
This is usually the result you want if your main goal is to find a relatively fresh egg.
However, I would not say that a sinking egg is automatically safe. The float test cannot tell you whether harmful bacteria are present.
2. The Egg Stands Upright
Sometimes an egg sinks but doesn’t lie flat. Instead, it rests on one end and points upward.
This usually means the egg is older.
The air cell has grown as the egg has aged, making it more buoyant. An upright egg isn’t automatically spoiled, though.
If I were checking one, I would move on to the next checks rather than throwing it away based only on its position.
3. The Egg Floats
If the egg rises to the surface, it has become quite buoyant.
This generally happens because the air cell has grown larger as the egg ages.
A floating egg is therefore usually older than one that lies flat.
But an egg that floats in water is not automatically rotten.
That’s one of the most useful things to know about the egg float test. Floating gives you information about age, but it does not give you a complete food-safety answer.
Why Does an Egg Float in Water?
The answer is inside the shell.
An egg has an air cell between its inner and outer shell membranes. This air space becomes larger as the egg ages.
Eggshells also contain tiny pores. Over time, moisture and gases move through these pores. The changes inside the egg affect its density and buoyancy.
As the air cell grows, the egg becomes more likely to stand upright or float.
You can think of the process like this:
Fresh egg
Small air cell → greater density → sinks
Older egg
Larger air cell → lower density → may stand upright
Older egg with a large air cell
More buoyancy → may float
This is why the egg floats in water as it gets older.
Does a Floating Egg Mean It Has Gone Bad?
No, not by itself.
This is where I would be careful with many simple egg freshness charts online.
The float test is useful for estimating age, but it does not detect every problem that can make an egg unsafe.
If an egg floats, I would consider:
- How it has been stored
- Whether the shell is cracked
- How long it has been refrigerated
- Whether it smells unusual after cracking
- Whether it looks abnormal
If you aren’t comfortable with the egg or don’t know how it was handled, discarding it is the safer choice.
What Should You Do With a Floating Egg?
If an egg floats, don’t immediately mix it into your recipe.
I would check it separately.
Step 1: Take It Out of the Water
Remove the egg and set it aside.
The floating result tells you that the egg is older. It does not tell you that you must automatically throw it away.
Step 2: Crack It Into a Separate Bowl
Crack the egg into a clean bowl instead of directly into your recipe.
This makes it much easier to inspect.
It also keeps one questionable egg from affecting the rest of your ingredients.
Step 3: Check the Smell
Give the cracked egg a careful smell.
A strong rotten or unpleasant odor is a clear reason to discard it.
Don’t try to cover the smell with other ingredients or use the egg anyway.
Step 4: Examine the Egg
Look at the egg white and yolk.
Older eggs can naturally have changes such as a thinner egg white. That doesn’t automatically mean spoilage.
However, if you notice something clearly unusual, I would discard the egg.
Step 5: Think About Storage
This step is easy to overlook.
The float test tells you about the egg’s physical changes. It does not tell you whether the egg was kept at a safe temperature.
If you don’t know whether an egg was stored properly, don’t rely on the float test alone.
Is the Egg Float Test Accurate?
It is useful, but only for a limited purpose.
The test works because egg freshness changes as the air cell grows. So it can help you tell whether an egg is relatively fresh or older.
It cannot tell you:
- The exact age of an egg
- Whether bacteria are present
- Whether an egg was stored correctly
- Whether a sinking egg is guaranteed safe
- Whether a floating egg is definitely spoiled
So I would describe it as a freshness indicator, not a complete safety test.
Can You Tell the Exact Age From the Float Test?
No.
You may see charts claiming that a particular egg position means an egg is exactly a certain number of days old.
I would not rely on those exact numbers.
Eggs can age differently depending on their storage conditions and other factors. The float test gives you a general clue, not a precise date.
For that reason, I prefer descriptions such as:
- Relatively fresh
- Older
- Quite old
rather than assigning an exact age to every position.
Freshness and Food Safety Are Different
This distinction deserves special attention.
An egg can be older without being spoiled.
At the same time, an egg that looks fresh in a float test isn’t automatically free from harmful bacteria.
So these are two different questions:
How old or fresh is the egg?
The float test can give you a clue.
Is the egg safe to eat?
That depends on more than its position in water.
Proper refrigeration, handling, shell condition, and cooking all matter.
This is why I would never use the rule:
Sink = safe
Float = unsafe
That rule is too simple.
Other Ways to Check an Egg
The float test is just one part of checking an egg.
Check the Smell
After cracking the egg into a separate bowl, check for an unusual or rotten smell.
A strong unpleasant odor is a reason to discard it.
Look at the Egg
Check the yolk and white for obvious changes.
Some differences can happen naturally as an egg gets older, so don’t assume every change means spoilage. Look for anything clearly abnormal.
Inspect the Shell
Before cracking an egg, look at the shell.
I avoid using eggs with cracked or leaking shells because damage can affect how the egg is protected.
Consider the Storage History
Ask yourself:
- Has the egg stayed refrigerated?
- Do I know how long I’ve had it?
- Was it left out for a long period?
- Was the shell damaged?
These questions can be more useful for food safety than the float result alone.
Egg Float Test Compared With Other Checks
| Check | Main purpose |
| Float test | Gives a clue about egg age |
| Smell check | Helps identify obvious spoilage |
| Visual check | Helps spot unusual changes |
| Shell inspection | Finds cracks or damage |
| Carton information | Helps track the eggs |
| Storage history | Gives useful handling information |
I would use these checks together rather than expecting one test to answer everything.
Should You Use Salt Water for an Egg Float Test?
I recommend sticking with plain water.
Salt changes the density of the water. That can change how an egg behaves in the bowl and make the result harder to interpret.
You don’t need salt to perform a basic egg float test.
Just use:
Plain water + egg + clean bowl
Keeping the test simple makes the result easier to interpret.
How Should You Store Eggs?
Proper storage matters whether an egg sinks, stands, or floats.
For refrigerated raw shell eggs, keep the refrigerator at 40°F (4°C) or below.
I also prefer keeping eggs in their original carton and storing them inside the refrigerator rather than on the door. The main compartment usually has a more stable temperature.
Raw shell eggs can generally stay refrigerated for around 3 to 5 weeks when stored properly.
If an egg has been sitting out for an unknown amount of time, I would not use the float test as a reason to assume it is safe.
What If an Egg Sinks but Looks Strange?
Don’t ignore other warning signs just because the egg sank.
A sinking egg is generally fresher than a floating egg, but the float test cannot guarantee safety.
If you crack an egg and notice a strong unpleasant odor or something clearly abnormal, discard it.
The same rule applies even if the egg sank during the water test.
What If an Egg Stands Upright?
An egg that stands upright at the bottom is generally older than one that lies flat.
The larger air cell makes it more buoyant.
I wouldn’t automatically throw it away based only on this result. Instead, crack it separately and check it before deciding what to do with it.
Egg Float Test for Backyard Eggs
The float test can also be used with backyard chicken eggs.
The same basic physical change happens as the egg ages, so the water test can still provide a freshness clue.
However, backyard eggs can have different collection and storage histories.
If you collect eggs yourself, keeping track of the collection date can be much more useful than trying to estimate age from the float test alone.
I would also pay attention to how the eggs were handled, cleaned, and stored.
Common Egg Float Test Mistakes
Mistake 1: Treating floating as proof of spoilage
A floating egg is generally older, but that result alone doesn’t prove that it has spoiled.
Mistake 2: Assuming sinking means guaranteed safety
A sinking egg is generally fresher, but the float test doesn’t detect harmful bacteria.
Mistake 3: Using salt water
Salt changes water density and can affect the result.
Mistake 4: Trying to calculate an exact egg age
The float test is not precise enough to tell you exactly when an egg was laid.
Mistake 5: Ignoring storage
An egg’s storage history matters. Don’t use the float test as a substitute for proper refrigeration and handling.
Egg Float Test: Quick Decision Guide
If you want a simple way to remember the results, use this:
Egg sinks and lies flat
Usually fresher
The egg has a smaller air cell and greater density.
Egg sinks but stands upright
Older egg
The air cell has grown, making it more buoyant.
Egg floats
Older egg
The air cell is larger. Check the egg separately before deciding whether to use it.
Any egg smells rotten or looks clearly abnormal
Discard it
Don’t try to save it by cooking it longer or adding it to another dish.
Final Thoughts
The egg float test is a handy way to get a quick idea of an egg’s age.
A fresh egg usually sinks and lies flat. An older egg may stand upright, while an even older egg may float. These changes happen because the air cell inside the egg becomes larger over time.
I would use the test as a starting point rather than a final decision. If an egg floats, check its storage history and inspect it separately after cracking. If it has a strong unpleasant smell, looks clearly abnormal, or you have doubts about how it was handled, discard it.
The key thing to remember is simple:
The egg float test can tell you something about freshness, but it cannot guarantee food safety.
Frequently Asked Questions
Do fresh eggs sink or float?
Fresh eggs generally sink and lie flat because they have a smaller air cell and are denser than water.
What does it mean if an egg floats in water?
A floating egg is generally older because its internal air cell has grown. Floating alone does not prove that the egg is rotten.
Can you eat an egg that floats?
A floating egg may still be usable, depending on its storage and condition. Crack it into a separate bowl and check for obvious signs of spoilage before deciding.
What does an upright egg mean?
An egg that stands upright on the bottom is usually older than one that lies flat. Its larger air cell makes it more buoyant.
Why do eggs float?
Eggs become more buoyant as they age because the air cell inside the shell grows. This reduces the egg’s density relative to the water.
Does the egg float test really work?
Yes, as a general freshness or age check. It does not work as a complete food-safety test.
Can the float test tell the exact age of an egg?
No. It can show that an egg has aged, but it cannot give you an exact age.
Should I use salt water to test an egg?
No. Plain water is better for a basic egg float test because salt changes the density of the water.
Can a sinking egg still be bad?
Yes. Sinking generally suggests a fresher egg, but it does not guarantee that the egg is safe or that it was stored correctly.
How long do eggs last in the refrigerator?
Raw shell eggs can generally be kept refrigerated for about 3 to 5 weeks when stored properly at 40°F (4°C) or below.
