The short answer: none. With the right adventure, you can sit down and run a game of D&D with zero preparation. That said, the experience at the table is always a little better with a few minutes of background, and ten minutes is plenty.
Most guides will tell you to budget thirty minutes to an hour of prep per session, sometimes far more. That's true if you're building a custom world from scratch and flipping through a stack of rulebooks. It doesn't have to be true for you.
Zero Prep: Just Grab an Adventure and Go
If you know the basics of gameplay, you can run a DnD Adventure Club adventure as you read it. No studying, no setup, no homework the night before.
Two things make this possible. First, the read-aloud blocks introduce each scene and action for you, so you always know what to say and what's happening next. You're guided through the story in real time. Second, every monster, spell, and magical effect is printed right there in the adventure, so you're never hunting through giant, expensive source books in the middle of a game. Everything you need is on the page in front of you.
That's the whole reason zero prep works: the adventure does the heavy lifting, so you can focus on having fun with your family.
Got 10 Minutes? Three Things That Make It Even Better
A little prep goes a long way. If you have ten minutes before game night, here are three quick things that will level up the experience for your players.
Grab characters and maps from our resource page. Our free resource page has more than 50 pre-built characters for your players to choose from, plus maps you can print out, both for your players and for you as the Game Master. Having these ready means everyone jumps straight into the story.
Practice the big three. Make sure you're comfortable running the three core rolls: an ability check, a roll to hit, and a saving throw. These three mechanics power nearly everything in the game, so a couple of minutes practicing them is the single highest-value thing you can do.
Know your big bad. Flip to the last page of the adventure and get to know the final boss before you start. Once you know where the story is headed, you can sprinkle in little hints and foreshadowing along the way. A little goes a long way, and it makes the finale land so much harder.
Bonus Prep: Keep a Few NPC Names Handy
Here's a small trick that feels silly but saves you every single time: come to the table with a list of about five NPC names.
Your players will always, always wander off and start talking to everyone they meet, the shopkeeper, the guard, the mysterious stranger in the corner. Having a name ready to go the moment they ask "what's her name?" keeps the story flowing and saves you from scrambling. It's thirty seconds of prep that makes you look like a pro.
The Bottom Line
You can run a great game of D&D with no prep at all, because the adventure is built to guide you through it. And if you have a few spare minutes, a tiny bit of background, some ready-made characters, the big three rolls, a peek at the villain, and a handful of names, turns a good game night into a great one. Either way, the barrier to starting is far lower than you've been led to believe.