Three full days are enough to see Tulum without rushing: the ruins, a couple of cenotes and the beach. Five if you also want to reach Cobá or Akumal. This is the split that works, hour by hour, assuming you are getting around on your own and not tied to anyone else's schedule.
First: two rules about timing
In Tulum the clock matters more than the map. Two things that shape any itinerary:
- Ruins and cenotes first thing. They open early, and the difference between 8am and 11am is crowds and heat, not price.
- Midday is for shade or for water. Between 1pm and 4pm, plan nothing that involves walking.
Day 1 · The ruins and your first beach
8:00 — The Tulum archaeological site. It opens then, and then is the best time: fewer people, less heat. You can walk it in just over an hour, and it is the only Mayan city built facing the sea.
10:00 — Down to the beach road, and stop at the first beach you like the look of. With your own vehicle you are not tied to whichever club is nearest.
14:00 — Lunch. Worth deciding with your head here: eating in town costs a fraction of eating in the hotel zone.
17:00 — An easy drive back and a first wander around town, which starts moving at about that hour.

Day 2 · Cenotes in the morning, town in the afternoon
8:30 — Breakfast in town.
9:30 — First cenote, along the Cobá road. Calavera if you want something quick with character; Gran Cenote if you want the classic — and then the earlier the better, because it fills up.
11:30 — Second cenote. Zacil-Ha or Car Wash, at the same point on the road and both open-air. Two cenotes in a morning is the right pace; three is a race. All five are in this cenote guide.
14:00 — Lunch and a nap. Not laziness, strategy.
18:00 — Town: market, shops and dinner. It is the easy evening of the trip.
Day 3 · A slow beach and the road at sunset
9:00 — Beach with no plan, whichever one you liked best on day one.
13:00 — Lunch at a beach club, which by then justifies the minimum spend.
17:00 — The beach road end to end, stopping wherever you feel like it, down to the southern tip. The full drive is in the sunset route.
20:00 — Dinner, then back along the main roads with your lights on.

If you have two more days
Five days makes room for Cobá — the pyramid in the jungle, an hour and a half by road — or Akumal and its turtle bay. Both are outside a cart's range, out on the federal highway, so they are car or organised-tour days. Better to put them together on a single car-rental day than to spread them out.
The itinerary in one line: day 1 ruins and beach · day 2 cenotes and town · day 3 slow beach and the road at sunset. All of it inside a cart's range, with no taxis and no tour timetables.
Quick questions
How many days do I need for Tulum?
Three full days cover the ruins, a couple of cenotes and the beach without rushing. Five if you add Cobá or Akumal.
Can this itinerary be done without your own vehicle?
It can, paying for every trip and fitting into other people's schedules. The sum is in what getting around Tulum costs.
What should I take each day?
Water, cash for entrance fees, a towel, something light for the ride back at night, and sunscreen you can wash off before entering a cenote.
And if I only have two days?
Merge day 1 and day 3: ruins early, beach at midday, the road at sunset. The cenotes wait for next time.
Putting it together
The only thing to settle before you arrive is what you will get around in; the rest can be decided on the day. If that is a cart, delivery happens at your hotel: see how the rental works, or go straight to checking your dates. And to get your bearings before the trip, the Tulum guide.