How the calculator estimates time

The calculator applies a classic heat-transfer model to estimate how long it takes for the center of an egg to reach a target temperature. The egg is modeled as a sphere and its contents approximated with a single thermal diffusivity. The formula is:

$$t=0.511\cdot M^{\frac{2}{3}}\cdot \ln \left(\frac{0.76\cdot \left(T,i,-,T,w\right)}{Tf-Tw}\right)$$

Here $M$ is the mass (grams), $Ti$ the initial temperature, $Tf$ the target yolk temperature, and $Tw$ the water temperature (assumed 100 °C). The logarithmic term captures how temperature approaches equilibrium over time.

Sample times

Size (g)	Soft (63 °C)	Jammy (70 °C)	Hard (80 °C)
50	6 min 10 s	7 min 30 s	9 min 30 s
60	6 min 40 s	8 min 10 s	10 min 15 s
70	7 min 05 s	8 min 50 s	11 min 00 s

Why egg size matters

Larger eggs take longer to cook because heat must travel farther to the center. The mass term raised to the two-thirds power reflects spherical conduction: surface area grows more slowly than volume, so doubling mass does not double cook time.

Starting temperature effects

Cold eggs require additional energy to reach the same yolk temperature. Select whether the eggs come straight from the refrigerator or have warmed on the counter to tailor the time accurately.

Choosing your doneness

Soft-boiled eggs thicken around 63 °C, jammy yolks set near 70 °C, and firm yolks form near 80 °C. Because carryover cooking continues after removal from the pot, plunge eggs into ice water to halt the process once the timer finishes.

Altitude adjustments

At higher altitudes water boils below 100 °C, lengthening cook times. Increase the result by roughly 5–10% per 1,000 m of elevation, or adapt the formula using your local boiling point.

Technique tips

Use an ice bath to make peeling easier and prevent overcooking. Cook eggs in a single layer with enough water to circulate around each shell. Gentle simmering rather than a rolling boil maintains consistent temperatures.

Energy awareness

Accurate timing saves energy and prevents sulfurous flavors caused by overcooking. After boiling eggs you can reuse hot water for tea or pasta to make the most of the heat you have generated.

Inside the Egg: Whites Versus Yolks

Heat affects albumen (egg white) and yolk at different rates because their proteins coagulate at different temperatures. Whites begin to firm around 62 °C while yolks stay fluid until they near 70 °C. The calculator’s target temperatures reflect these transitions so you can decide whether you prefer a runny center or a fully set yolk. Knowing that yolks lag behind whites also explains why plunging eggs into cold water locks in texture—the rapid cooling halts the carryover cooking that would otherwise push the yolk past your desired doneness.

Adapting for Altitude and Equipment

Water boils at lower temperatures as altitude increases, which lengthens cook times beyond what the base formula predicts. At 5,000 feet (1,524 m), boiling point drops to roughly 202 °F (94.4 °C), extending the cook by almost a minute for large eggs. Induction cooktops, gas burners, and electric coils also deliver heat differently; the calculator assumes a steady boil, so if your pot loses heat quickly when the eggs go in, allow an extra 30–60 seconds for recovery.

Altitude (ft)	Boiling Point (°F)	Suggested Time Adjustment
Sea level	212	Base calculation
2,500	207	Add 30 seconds
5,000	202	Add 60 seconds
7,500	198	Add 90 seconds

Batch Cooking and Meal Prep

If you boil multiple eggs for weekly meal prep, keep track of pot size and water depth. Crowded pots retain more heat and sometimes lead to uneven results if eggs stack on top of one another. Consider weighing a representative egg before and after boiling to verify the calculator’s prediction. Recording results in a journal lets you fine-tune the coefficient for your preferred brand or egg size.

Testing Doneness Without Cracking

Spinning an egg on the counter is a classic trick: hard-boiled eggs spin smoothly, while soft-boiled eggs wobble as the liquid center shifts. Another technique is to hold the egg up to a bright light; translucent patches indicate a runny yolk. These observations are qualitative, but they validate whether the calculator’s estimate matches your actual stove and cookware.

Food Safety Considerations

Use pasteurized eggs if you plan to serve soft-boiled yolks to individuals with weaker immune systems. Rapidly chilling cooked eggs in ice water not only stops cooking but also keeps them below the bacterial “danger zone” sooner. Store peeled eggs in sealed containers with just enough water to keep them moist, and consume within one week for best quality. The calculator’s emphasis on precise timing helps ensure yolks reach temperatures high enough to deactivate common pathogens without drifting into overcooked territory.

Flavor Enhancements

Seasoning starts before cooking. Adding a teaspoon of baking soda raises alkalinity, making shells easier to peel, while a splash of vinegar minimizes egg white seepage if a shell cracks. After boiling, consider marinating eggs in soy sauce, pickling brine, or smoky tea to add depth. Because the calculator standardizes the core timing, you can confidently explore these variations without worrying about inconsistent textures.

Keeping a Boiling Log

Print or save your results using the Copy button, then jot down notes about pot size, heat source, and outcomes. Over time you’ll build a personal dataset that reveals how subtle tweaks affect texture. Sharing that log with other cooks or students illustrates applied heat-transfer principles in an accessible, everyday context.