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About this tool
Time boiled eggs exactly how you like them, adjusted for egg size, fridge chill, and altitude.
Perfect Egg Timer works out how long to cook a boiled egg by taking a base time for the yolk you want — 6:00 soft, 7:00 jammy, 8:00 medium, 10:00 hard, 12:00 very hard — and adjusting it for egg size, whether the egg came out of the fridge, boiling versus steaming, and your altitude. The base times assume a large egg, fridge cold, lowered into already-boiling water at sea level, and the running countdown uses a fixed finish timestamp so it stays accurate in a background tab. It shows every adjustment as a separate line so you can see exactly where the minutes came from.
Open Perfect Egg Timer on AltFTool — it loads instantly in your browser.
Under "How do you want the yolk?" pick Soft 6:00, Jammy 7:00, Medium 8:00, Hard 10:00 or Very hard 12:00 — the base times assume a large, fridge-cold egg lowered into boiling water at sea level.
In Adjustments choose Egg size (Small, Medium, Large or XL), Starting temperature (Fridge cold or Room temp), Method (Boiling water start or Steam) and drag the Altitude slider up to 3,500 m.
Total cook time updates with each adjustment itemised; press Start timer to run the countdown, with Pause, Resume and Reset available, and an "Ice bath now!" prompt at zero. Copy plan copies the timing.
The breakdown lists base time, size, starting temperature, method and altitude separately, then totals them.
The timer stores an absolute end time rather than counting ticks, so backgrounding the tab does not slow it down.
A three-beep tone fires at zero with a reminder to chill immediately, because carry-over heat is what turns a jammy yolk chalky.
Six minutes for a large, fridge-cold egg lowered into water already at a rolling boil. A jammy, custardy centre takes 7 minutes, medium 8, hard 10 and very hard 12 — then adjust for your egg size and method.
Yes. Working from a large egg (about 60 g) as the baseline, a medium egg needs 30 seconds less, a small egg a full minute less, and an XL egg 30 seconds more. Room-temperature eggs also come off 30 seconds because they start closer to setting temperature.
Add roughly 30 seconds per 500 m above 1,000 m. Below 1,000 m no correction is applied; water boils at a lower temperature as you climb, so the same time delivers less cooking. At 2,500 m that works out to about 90 extra seconds.
Usually because they are too fresh or were not chilled fast enough. Eggs a week or two old have a higher internal pH and release from the membrane far more easily, and 10 minutes in iced water contracts the egg away from the shell. Steaming also sets the outer white before it bonds to the membrane, which is why this tool adds 30 seconds for the steam method.