how long does it take for a happy ghast to rehydrate

A dried ghast takes about 20 minutes in water to fully rehydrate into a ghastling, and that ghastling then needs another 20 minutes to mature into a happy ghast, for a total of roughly 40 real‑time minutes if you do the whole process in one go.

Quick Scoop

• A dried ghast block must stay continuously submerged in water for about 20 minutes to finish its rehydration stages and turn into a ghastling.

• During those 20 minutes you see clear stages: partially hydrated at ~5 minutes, mostly hydrated at ~10, visually “complete” at ~15, and the actual ghastling appears at ~20.

• Once you have a ghastling, it takes around another 20 minutes of in‑game time to grow into a happy ghast, unless you speed that up with mechanics like feeding snowballs where supported.

• If the water is removed at any point while the dried ghast is rehydrating, the timer will start ticking backward at the same rate, so it effectively “un‑hydrates” instead of progressing.

• Some players report the process feeling random because it depends on the chunk being loaded and on random ticks, so if you walk too far away or the area is not simulated, the rehydration seems to stall.

Little forum‑style note

“Contrary to popular belief, the happy ghast’s rehydration is random… The timer is 16:40 split into 4 segments… but a random tick is required to start each one.”

So in practice, if your world is loaded and you stay within simulation distance, plan on about 40 minutes total from dried ghast in water to a fully grown happy ghast, with minor variation depending on random ticks and your platform/settings.

TL;DR: Keep the dried ghast in water for ~20 minutes to get a ghastling, then wait another ~20 minutes for it to grow into a happy ghast, without unloading the area or removing the water.

Information gathered from public forums or data available on the internet and portrayed here.