How much sleep do you actually get before the Mount Rinjani sunrise summit climb?

Realistically you get six to seven hours in bed, and somewhat less than that in actual sleep, so plan around the deficit rather than pretending it does not exist. A standard schedule reaches the Sembalun rim camp around 15:30 to 16:00 in the afternoon, and the wake-up call comes at 02:00 to 02:30 for the summit push. If you are genuinely horizontal by 19:00 or 20:00, the arithmetic gives you six to seven hours in the sleeping bag, but that figure comes before you subtract tent setup, dinner, washing up, changing clothes, the noise of a crowded camp, and the wind flapping the fly.

The controllable part is everything you do before dinner. Decide at daylight what you need for the summit, because that is the moment your brain still works: lay out your summit layers, fill your water, set out your headlamp and gloves, and pack the small day bag you will carry to the top. Eat dinner early, drink generously since the summit climb is dehydrating work in cold air, and get into the sack as close to 19:00 as the group’s routine allows. Trekkers who are still socializing at 21:30 are the ones staring at the ceiling at 01:45.

Ask your guide two questions the evening before. What is the actual wake-up time for your group, since it shifts with the season’s sunrise and the guide’s judgment about your pace, and what happens after the climb, because knowing that breakfast and a nap wait at camp changes how you spend yourself on the summit slope. Then accept the truth every guide knows: you will start the summit climb tired, everyone does, and tired-but-prepared beats rested-and-chaotic every time. The climbers who summit well are the ones who treated the first night as part of the climb and went to bed like it mattered. Six hours of real rest carries most people up this route, but only the ones who did the preparation.