Egg Freshness Calculator

How to tell if eggs are still good

The float test is the most popular method and the most misunderstood one. An egg that floats is not automatically rotten. An egg that sinks is not automatically fresh. The test measures the size of the air cell, which grows as moisture evaporates through the shell over time. Here is what each result actually means.

Quick context on who built this. I am a software developer, not a lifelong chicken keeper. I built Flockmath because most online answers to "are my eggs still good?" jump straight to "if it floats, throw it out" without explaining what the float test actually measures. The calculator above estimates age from your lay date and storage method, then predicts the float result so you know what to expect before the egg ever hits the water. The float test is still the final word — this just tells you what is normal for an egg of that age.

The float test explained

Place the egg in a bowl or glass of cold water deep enough for the egg to be fully submerged.

What you see and what it means:

• Egg sinks and lies flat on the bottom: 1 week old or less. Best possible result for frying, poaching, or any preparation where freshness shows.
• Egg sinks but the large end tilts upward slightly: 1 to 2 weeks old. Still excellent quality.
• Egg sinks but stands at a noticeable angle or nearly upright: 2 to 3 weeks old. Good for all cooking. Slightly easier to peel when hard-boiled (older eggs peel better).
• Egg bobs just above the bottom or floats with part above the waterline: 4 to 5 weeks old. Smell before using. If it smells fine, it is almost certainly fine.
• Egg floats entirely: 6+ weeks old at room temperature. Discard. At this age the air cell is very large and the egg is likely past safe consumption.

Room temperature vs refrigerated — a genuine difference

Outside the US, most people store eggs at room temperature and consider them fresh for 2 to 4 weeks. This works because unwashed eggs retain their natural cuticle (called the bloom), which seals the porous shell and slows moisture and bacteria penetration.

In the US, commercial eggs are washed — removing the bloom — making refrigeration necessary to prevent bacterial growth. If you have backyard chickens and do not wash the eggs, room-temperature storage for 2 to 4 weeks is perfectly safe and is how most of the world stores eggs.

If you do wash your eggs before storing, refrigerate them. Washing removes the bloom and the egg is then vulnerable to bacteria at room temperature.

Water glassing — the long-term storage method

Water glassing uses a solution of calcium hydroxide (pickling lime) and water to seal unwashed fresh eggs for long-term storage. Properly water-glassed eggs in a sealed container stay edible for 12 to 18 months at cool room temperature.

The process requires fresh, unwashed, uncracked eggs and clean water. The lime solution coats the shell and prevents moisture loss and bacterial entry. It was the standard egg preservation method before refrigeration.

Water-glassed eggs work fine for baking and cooking. They are not ideal for frying sunny-side up because the texture changes slightly. But for an omelette, cake, or scrambled eggs the difference is undetectable.

Best uses for eggs at different stages

Very fresh (under 1 week): poaching, frying, soft-boiling — anywhere presentation matters and the texture of a fresh yolk is noticeable.

Fresh (1 to 3 weeks): all uses. No meaningful quality difference for most cooking applications.

Use soon (3 to 5 weeks): scrambling, baking, hard-boiling. Notably easier to peel when hard-boiled — this is one practical advantage of slightly older eggs.

Past peak (5+ weeks at room temp, smell test first): baking where the egg is one of many ingredients. If it smells fine, it is almost certainly fine to use. A bad egg has an unmistakable sulfur odor. There is no such thing as a bad egg that does not smell bad.

Common mistakes

1. Assuming a floating egg is rotten and discarding it without smelling it. A floating egg has a large air cell, which means age — not necessarily spoilage. Smell it first.
2. Refrigerating washed eggs on the counter, then putting them back in the fridge. Temperature cycling accelerates moisture loss.
3. Storing eggs near strong-smelling foods in the fridge. Eggshells are porous and eggs absorb odors.
4. Not dating the eggs when you collect them. A simple pencil mark with the collection date on the egg takes 2 seconds and saves all the guessing this calculator is designed to help with.
5. Discarding good eggs because of a cracked shell. A cracked egg should be used within 2 days if refrigerated, but it is not unsafe to use immediately.

Where to go next

Knowing how fresh your eggs are is one piece of the backyard egg picture. A few connected calculators:

• The Egg Production Calculator estimates how many eggs your flock will lay each week and year, so you know how fast the carton fills up in the first place.
• The Feed Consumption Calculator tells you what those eggs cost to produce, broken down by breed and life stage.
• The First-Year Cost Calculator adds up the full startup cost of a flock — coop, birds, equipment, and feed — plus your year-two operating cost.