The honest answer is 45 minutes to an hour for most people. But that number hides the thing that actually decides it, which is not how fast you walk — it is how much of the site you know is there.
El Badi is not a building you move through room by room. It is a walled rectangle of open ground the size of several football pitches, with the interesting parts spread around its edges and below it. Someone who walks in, photographs the great pool and leaves has seen perhaps a third of it in twenty minutes and will tell you the palace is empty. Someone who knows about the underground gallery and the rooftop stairs spends ninety minutes and leaves thinking it was the best thing they did in Marrakech.
So here is what each amount of time actually buys.
Thirty minutes: the courtyard and the pool
Enough for the entrance corridor, the sunken orange gardens, and the great reflecting pool with the ramparts behind it. This is the photograph everyone comes for and it is near the entrance, so thirty minutes is genuinely enough to get it and go.
What you miss is everything that explains the place. The reason El Badi is a shell rather than a palace is not visible from the courtyard, and neither is the Koutoubia minbar, which is the single most valuable object on the site.
An hour: the main circuit
An hour lets you walk the full rectangle rather than cutting across it. That adds the arched niches along the far wall, the excavated zellij courtyard where the original floor survives in patches, and the pavilion holding the Koutoubia minbar.
This is the pace most visitors settle into without planning it, and it is a reasonable one. You see the whole site, you read the information panels, and you are not rushing the parts that reward standing still.
Ninety minutes: the parts most people skip
Two things take El Badi from a large empty courtyard to a place worth the walk, and both are easy to miss.
The underground gallery runs beneath the pavilions — cool, dim corridors that were storage and service passages when the palace was in use. Nothing outside signals how much of it there is.
The rooftop terrace is reached by stairs at the far end. From up there the layout finally makes sense: you can see the pools as a plan rather than as obstacles, and you get the storks nesting on the ramparts at eye level, which is the view most people remember.
Neither is signposted in a way you would notice while heading for the exit. If you have ninety minutes, spend the last thirty on these.
Fitting it into a day
Ninety minutes is the ceiling, not a target, and that is useful to know when planning. The Saadian Tombs are a short walk away and take about forty minutes; the Kasbah district is right there. A morning that starts at El Badi at opening time can comfortably cover both before lunch — see the one-day Marrakech itinerary for how that fits together.
The one thing that ruins the timing is arriving late. Opening hours are 9:00 to 17:00 with last entry around 16:30, and the terrace stairs are the first thing you will decide to skip when you are watching the clock.
When to go, not just how long
Time of day changes how long you will want to stay more than you would expect. In the middle of a summer afternoon there is almost no shade in the main courtyard, and ninety minutes becomes forty by choice rather than by plan. Early morning and the last two hours before closing are both cooler and better for photographs — the best time to visit goes into the seasonal detail.
If you are visiting with children, halve every number above and plan around the ramparts and the storks rather than the ruins; there is more on that in El Badi Palace with kids.