Free Egg Boiling Time Calculator

Mastering Egg Boiling Times: Science, Altitude, and Practical Tips

Knowing exactly how long to boil eggs to get your preferred doneness—whether a soft, runny yolk or a fully set hard yolk—can be surprisingly tricky. The perfect boiled egg time depends on egg size, its starting temperature, your elevation above sea level, and the target doneness. This egg boiling time calculator applies heat‑transfer physics to remove the guesswork, delivering a precise cooking time tailored to your specific conditions. Whether you’re looking for a soft boiled egg time with a creamy center or a reliable hard boiled egg time, the tool accounts for every variable.

The Essential Steps

1. Bring a pot of water to a full, rolling boil. Adding about half a teaspoon of salt can help reduce the chance of shells cracking.
2. Use eggs that have been out of the refrigerator for a few minutes—eggs taken straight from the fridge are more prone to cracking.
3. Gently lower the eggs into the water. Make sure the water remains boiling; start your timer immediately after the eggs go in.
4. When the timer ends, transfer the eggs to a bowl of cold water (or run them under cold tap water) to halt the cooking process.

What Happens Inside the Shell

Egg white coagulates (turns from liquid to solid) at a slightly lower temperature than the yolk. For a soft‑boiled egg, the white should be firm while the yolk stays runny—this happens when the center reaches about 65 °C (149 °F). For a hard‑boiled egg, the yolk must fully thicken, but the temperature should remain below 77 °C (170.6 °F) to avoid the formation of ferrous sulfide, which creates a greenish layer around the yolk.

The cooking time is governed by heat diffusion from the shell inward. A classic model developed by Charles Williams of the University of Exeter relates the time $t$ to the egg’s properties:

$$t = K \cdot m^{2/3} \cdot \frac{1}{\text{ywr}} \cdot \ln\left(\frac{T_{\text{water}} - T_{\text{egg}}}{T_{\text{water}} - T}\right)$$

where
$m$ = egg mass,
$K$ = a thermal‑property constant of the egg,
$T_{\text{egg}}$ = initial egg temperature,
$T_{\text{water}}$ = boiling point of water (which changes with altitude),
$T$ = target temperature at the white‑yolk boundary,
$\text{ywr}$ = white‑to‑yolk ratio.

When you remove the egg from hot water, the outer white (still near 100 °C / 212 °F) continues to transfer heat inward. Immediate cooling stops this carryover cooking, keeping the yolk from overcooking.

How Altitude Rewrites the Rules

Air pressure decreases as elevation increases, lowering water’s boiling point. This lower cooking temperature means the egg needs more time to reach the desired doneness—a key aspect of egg cooking time by altitude.

• At sea level, water boils at 100 °C (212 °F).
• At 4,150 m (El Alto, Bolivia), the boiling point is about 85.9 °C (186.6 °F). Soft‑boiling an egg here takes roughly 2 minutes longer than at sea level.
• At the summit of Mount Everest (8,848 m), water boils at only 68 °C (154.5 °F), making a hard‑boiled egg impossible—the yolk cannot reach its coagulating temperature.

The calculator automatically adjusts the cooking duration based on your altitude, giving consistent results whether you’re cooking at sea level or high in the Andes.

Reference Times at Sea Level

The following approximate times are for a medium egg straight from the refrigerator, cooked at sea level. Actual times will change with egg size, starting temperature, and altitude—use the calculator for a precise value.

Doneness	Yolk Center Temperature	Approximate Time
Soft (runny yolk)	65 °C (149 °F)	4–5 min (varies with size)
Medium (semi‑set yolk)	70 °C (158 °F)	~6 min
Hard (fully set yolk)	77 °C (170.6 °F)	~9 min 30 s

Quick Peeling Hacks

Once the egg is cooked and cooled, peeling can be effortless with these tricks:

• Blow method – Crack both ends of the egg and blow firmly to push the egg out of its shell.
• Shake method – Place the egg in a sealed container with a little water and shake vigorously; the shell will slip off.
• Roll method – Crack the egg and roll it on a countertop, then peel under cold running water.

All three techniques rely on the temperature change shrinking the egg slightly, separating the membrane from the shell.