Perfect Egg Boiling Calculator
Example: 60g egg from fridge at sea level = 6:30 for soft
Estimate an egg's boiling time based on its size, starting temperature, altitude, and desired doneness. The calculation uses heat diffusion principles and accounts for water boiling at lower temperatures at higher altitudes. It supports soft-boiled, medium, and hard-boiled eggs.
Boil time vs. 15-min timer
Runny to hard, by minute
Boiling Time
Time after water reaches boiling
Water Boiling Point
Boiling temperature at your altitude
Target Yolk Temperature
Desired internal temperature
Egg Weight Used
Weight for calculation
How We Calculate This
Time is calculated using a heat diffusion model: t = K × mass^(2/3) × ln((Tboil - Tstart) / (Tboil - Tyolk)). Boiling point decreases ~0.3°C per 100m altitude. Yolk targets: soft 63°C, medium 70°C, hard 80°C.
Methodology last reviewed: March 2022. How SparkCalc works
Sources: U.S. FDA: What You Need to Know About Egg Safety · Institute of Food Science and Technology: Protein: Coagulation
Frequently Asked Questions
Why does altitude affect boiling time?
At higher altitudes, atmospheric pressure is lower, causing water to boil at a lower temperature. At 3,000m elevation, water boils at about 90°C instead of 100°C. The lower temperature means eggs cook more slowly.
Should I start with cold or boiling water?
This calculator assumes you're adding eggs to already boiling water, which gives more consistent results. If you start with cold water and heat together, timing becomes less predictable.
Why do more eggs need slightly longer?
Adding multiple eggs temporarily lowers the water temperature. While the water quickly returns to boiling, the brief temperature drop can slightly extend cooking time. We add about 30 seconds for batches over 6 eggs.
Why is an ice bath recommended?
Immediately transferring eggs to ice water stops the cooking process and prevents the grey-green ring around the yolk. It also causes the egg to contract slightly from the shell, making peeling easier.
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