Egg Boiling Time Calculator

Background.

This calculator estimates how many minutes to boil an egg for a soft, medium, or hard yolk, adjusted for egg size and altitude. The result is an estimate for a rolling boil at the stated egg size and elevation — actual timing still depends on starting egg temperature (straight from the fridge versus room temperature), how vigorously the water boils, and personal taste for exactly how set a yolk should be.

Altitude matters more than most home cooks expect, because water simply does not get as hot at elevation. At sea level, water boils at 212°F. At 5,000 feet, it boils at roughly 203°F — about 9°F cooler — because atmospheric pressure is lower and water needs less added energy to turn to vapor. A pot of water at a rolling boil in Denver is genuinely cooler than a pot of water at a rolling boil in Miami, even though both look identical. Since cooking speed depends on temperature, not just on the visual fact of boiling, an egg cooked for exactly 12 minutes in Miami will be less done than the same egg cooked for 12 minutes in Denver. USDA FSIS's high-altitude cooking guidance addresses this directly: add roughly one additional minute of boiling time for every 1,000 feet of elevation above about 3,000 feet, which is the adjustment this calculator applies automatically.

Egg size is the other major variable, and it scales fairly predictably: a well-corroborated hard-boiled-egg timing chart gives medium eggs about 9 minutes, large eggs about 12 minutes, and extra-large eggs about 15 minutes at sea level — ratios of 0.75, 1.00, and 1.25 relative to a large egg. This calculator applies those same size ratios across soft, medium, and hard doneness levels, since no separate published chart exists for every size-doneness combination; it's a reasonable proportional estimate, not a separately verified figure for every cell, and this page says so plainly rather than presenting invented precision.

Doneness itself is really a spectrum along one dimension: how far heat has penetrated from the white toward the center of the yolk. A soft-boiled egg has a fully set white but a still-liquid, pourable yolk. A medium-boiled egg (sometimes called 'jammy') has a white fully set and a yolk that has thickened into a soft, spreadable paste but is not solid. A hard-boiled egg has both white and yolk completely firm all the way through. Longer time in the same boiling water moves an egg further along this spectrum; there is no trick beyond time and starting temperature that changes which doneness you land on.

A safety note belongs on this page because it is genuinely relevant: the FDA advises that infants, young children, older adults, pregnant people, and people with weakened immune systems should avoid eggs with runny or undercooked yolks and whites, because a soft or liquid yolk has spent less time at temperatures that reliably kill Salmonella if present. For those groups, hard-boiled — whites and yolks both fully firm — is the safer choice, regardless of what this or any other calculator estimates for soft or medium timing.

What is egg boiling time calculator?

An egg boiling time calculator estimates how many minutes an egg needs in boiling water to reach a chosen doneness — soft, medium, or hard-boiled — accounting for egg size and altitude. It exists because 'boil an egg for N minutes' is a common piece of kitchen folklore that quietly assumes a specific egg size and sea-level atmospheric pressure, both of which vary in the real world.

The calculator starts from a base sea-level time for a large egg (soft 6 min, medium 9 min, hard 12 min), scales that time for smaller or larger eggs using a size ratio anchored to a widely corroborated hard-boil chart, and then adds time for elevation, since water boils at a lower, less effective temperature the higher up you cook. The altitude adjustment follows USDA FSIS's published high-altitude cooking guidance: roughly one added minute of boiling time per 1,000 feet above about 3,000 feet.

How to use this calculator.

1. 01Select your egg size: medium, large, or extra-large.
2. 02Select your target doneness: soft, medium, or hard-boiled.
3. 03Enter your altitude in feet — use 0 if you're not sure and you're near sea level.
4. 04Read the estimated boiling time in minutes.
5. 05Start timing once the water returns to a full rolling boil after the eggs go in.
6. 06For infants, young children, older adults, pregnant people, or anyone immunocompromised, choose hard-boiled — fully firm whites and yolks.

The formula.

The calculator starts with a base time for a large egg at sea level: 6 minutes for soft, 9 minutes for medium, 12 minutes for hard, at a rolling boil. That base time is multiplied by a size ratio — 0.75 for medium eggs, 1.00 for large eggs, 1.25 for extra-large eggs — derived from the widely corroborated hard-boiled-egg chart (medium 9 min / large 12 min / extra-large 15 min, which reduces to exactly those three ratios). For a medium hard-boiled egg, that is 12 × 0.75 = 9.0 minutes; for an extra-large soft-boiled egg, 6 × 1.25 = 7.5 minutes.

The altitude adjustment is added on top, not multiplied in, because it reflects a genuinely different physical effect: water's boiling point itself dropping with elevation, per USDA FSIS's high-altitude cooking guidance of roughly one extra minute of boiling time per 1,000 feet above about 3,000 feet. Below that 3,000-foot threshold, no adjustment is applied. At 6,000 feet, the adjustment is (6000-3000)/1000 x 1 = 3 additional minutes; a large hard-boiled egg that takes 12 minutes at sea level takes about 15 minutes at 6,000 feet.

The calculator also reports an approximate boiling point at the chosen altitude, using the commonly cited linear approximation that water's boiling point drops about 1.8°F for every 1,000 feet of elevation — 212°F at sea level down to roughly 203°F at 5,000 feet, consistent with the physical relationship between atmospheric pressure and boiling point (the Clausius-Clapeyron relationship). This number is shown for context, to make visible WHY altitude changes cooking time, not as a separate adjustment to be applied on top of the minutes already calculated.

A worked example.

Frequently asked questions.

References& sources.

1. [1]U.S. Department of Agriculture, Food Safety and Inspection Service. "High Altitude Cooking." FSIS.
2. [2]Colorado State University Extension. "High Elevation Food Preparation Guide."
3. [3]MedlinePlus, National Library of Medicine, National Institutes of Health. "Perfect Hard-Cooked Eggs."
4. [4]U.S. Food and Drug Administration. "What You Need to Know About Egg Safety." FDA.