Egg Cooking Time Calculator
Find the ideal boiling time for a perfect soft, medium, or hard-boiled egg based on egg size and your preferred doneness. Removes the guesswork from one of cooking's most precise tasks.
Last updated: September 2026
Cooking Time
3.38 minutes
Formula below · 2 sources (fdc.nal.usda.gov, Wikipedia) · Updated Sep 2026
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About this calculator
Egg cooking time depends on the mass of the egg and how set you want the yolk and white. This calculator uses a base cooking time adjusted by an egg size factor. The formula is: cookingTime = baseTime + (baseTime × 0.125 × eggSize). Here, baseTime represents the starting duration for a small egg at your chosen doneness, and eggSize is the size factor (1 small, 1.2 medium, 1.4 large, 1.6 extra-large), so each egg gets an extra 12.5% × size factor of the base time, accounting for the greater thermal mass of larger eggs. The underlying physics is heat conduction through the albumen to the yolk center; larger eggs simply require more time for the heat to penetrate fully. Food safety: the USDA advises cooking eggs until both the yolk and white are firm; soft- and medium-boiled eggs with runny yolks carry a small Salmonella risk, so use pasteurized eggs for young children, older adults, pregnant people and anyone with a weakened immune system.
How to use
Imagine you want a medium-boiled large egg: base time 6 minutes, size factor 1.4. cookingTime = 6 + (6 × 0.125 × 1.4) = 6 + 1.05 = 7.05 minutes, about 7 minutes from when the egg goes into boiling water, for a jammy yolk. For a hard-boiled extra-large egg (base 10, factor 1.6): 10 + (10 × 0.125 × 1.6) = 12 minutes. Cool the eggs in ice water immediately to stop the cooking.
Frequently asked questions
How does egg size affect boiling time for soft or hard-boiled eggs?
Larger eggs contain more mass, so heat takes longer to reach the center of the yolk. In this calculator an extra-large egg gets about 7.5% more time than a small one at the same doneness (for example 7.2 versus 6.75 minutes at the 6-minute base). Starting temperature matters too: eggs straight from the refrigerator take a little longer than room-temperature eggs. Ignoring size and starting temperature is one of the most common reasons for unexpectedly runny or overcooked eggs.
Should I start eggs in cold water or boiling water for accurate cooking times?
Starting eggs in already-boiling water gives far more consistent and predictable results, and most precise cooking-time formulas — including this one — assume you lower the egg into simmering or boiling water. Cold-start methods involve a variable heating phase that differs by pot, stove, and water volume, making timing unreliable. If you prefer the cold-start method, add approximately 1–2 minutes to the calculated time and expect some variation. For perfect precision, use boiling water and a timer.
Why do altitude and water temperature affect egg boiling times?
At higher altitudes, atmospheric pressure is lower, which causes water to boil at temperatures below 100 °C (212 °F). At 2,000 meters above sea level, water boils at roughly 93 °C, meaning less heat energy is transferred to the egg per minute. As a result, eggs take noticeably longer to cook at altitude — sometimes 20–30% more time than at sea level. If you live or cook above 1,500 meters, you should add extra time beyond the calculator's output or use a pressure cooker to restore full boiling temperature.