Egg Boiling Time Calculator
How long to boil an egg for a runny, jammy or hard yolk, adjusted for its size, whether it came from the fridge, and your altitude.
Times are for eggs lowered into already-boiling water: about 6 minutes for a soft, runny yolk, 7½ for jammy, 10 for hard, for a large egg straight from the fridge.
How the egg boiling time calculator works
Times are for eggs lowered into already-boiling water: about 6 minutes for a soft, runny yolk, 7½ for jammy, 10 for hard, for a large egg straight from the fridge. Smaller eggs need less, extra-large more; a room-temperature egg saves half a minute. Water boils cooler at altitude, so add roughly a minute per 1,000 m. Plunge into cold water to stop the cooking.
Formula: time = base (soft 6 / jammy 7½ / hard 10 min) + size adjustment + start-temperature adjustment + altitude
Worked examples
| Inputs | Boil for | Note |
|---|---|---|
| Jammy large egg from the fridge | 7.5 min | 7.5 min |
| Hard-boiled medium egg at room temperature | 9 min | 9 min |
| Soft-boiled at 1,500 m | 7.5 min | 7.5 min |
FAQFrequently asked questions
Should eggs start in cold or boiling water?
These times are for eggs lowered into water at a rolling boil, which gives repeatable results. Starting cold works too but is harder to time; hard-boiled eggs started cold are less likely to crack.
Why do fridge-cold eggs take longer?
They start about 20 °C cooler, so they need roughly half a minute more to reach the same yolk temperature. Cold eggs also crack more readily — a pinhole in the round end helps.
How do I stop the green ring on hard-boiled yolks?
Do not overcook — ten minutes is enough — and cool the eggs quickly in cold water. The grey-green layer is iron sulphide from prolonged heating.
Why does altitude matter?
Water boils cooler at altitude, so the egg cooks more slowly: add roughly a minute per 1,000 m of elevation, as the calculator does.
Where these figures come from
- US FDA — Safe Minimum Internal Temperatures — the internal temperatures the roasting calculator targets
- NIST SP 811 — Guide for the Use of the International System of Units — the exact weight and volume conversions used throughout
- UK Food Standards Agency — food safety and labelling standards
Last checked: September 2026. Baking ratios follow standard baker's percentage practice; roasting guidance follows published safe internal temperatures.