Ten days is the right amount of time to see the south coast properly. You can cover the main towns without rushing, add a safari, have a few days where you do nothing except swim and eat, and still leave with a clear sense of what the coast is actually like. Here is a route that works for most travellers and can be adjusted depending on your pace.
Days 1 and 2: Galle. Arrive and stay at least two nights. One morning for the fort, one afternoon for the ramparts and the back lanes. The second day can be slower: Jungle Beach in Unawatuna, a long lunch somewhere good, an evening walk along the walls. Galle is a place that rewards taking your time. Two nights is the minimum to feel it rather than just see it.
Days 3 and 4: Ahangama. Move 15 minutes east along the coast. Ahangama is quieter than Galle, has excellent cafes, and the surf at Kabalana is a step up in quality from Weligama for anyone past the beginner stage. If you do not surf, use it as a base to eat well and slow down. Two nights here is enough.
Days 5, 6 and 7: Weligama. The middle of the coast and the most practical base on it. Spend three nights. Day trip to Mirissa on one of those days, specifically to see Secret Beach and Coconut Tree Hill in the early morning. Day trip to Polhena on another day for snorkelling with turtles. The third day in Weligama itself: the beach, the bay, a surf lesson if you have not yet done one. Weligama is not the most dramatic stop on this route but it is the most comfortable, and comfort mid-trip matters.
Days 8 and 9: Hiriketiya. About 30 minutes east of Weligama toward Dickwella. A small horseshoe bay with consistent surf, no nightlife, and some of the best cafes on the coast. Come here to slow down and stay slow. Two nights is right for most people. If the surf is good and you are a surfer, three nights will not feel like too long.
Day 10: Move toward Tangalle or start the return. Tangalle is another 30 minutes east of Hiriketiya and has a completely different character: a sprawling wild bay, rough sea for walking rather than swimming, and a quieter, older version of the coast. It is worth a morning visit or a final night before heading back north. If you are flying from Colombo the next day, Tangalle is a good place to spend a final evening, and the drive or taxi north the following morning takes around three to three and a half hours.
What this route skips. Tissamaharama and Yala are possible from this route but add at least two days. If you want a safari, extend the trip to twelve days and add it between days 9 and 10: one night in Tissa, an early morning safari at Yala, then west to Tangalle. Udawalawe is better suited to a trip where you have already been to Ella and are heading down to the coast, which is covered in a separate guide.
The route above is deliberately unhurried. There are only five bases in ten days. That is the right pace for the south coast. You will not see everything, but you will actually see the things you do stop at.
We put together versions of this route all the time, adjusted for specific dates, travel styles, and whether you need a private driver or are happy on buses.