How much time in Barcelona?

Not for me it isn't. Of course, each traveler gets to decide what the "primary sights" are. I recommend getting at least one guidebook covering Barcelona, reading about the sights and deciding which ones you don't want to miss.

Barcelona is trickier than many cities in that so many of its top sights require timed entry tickets (and many sell out before the end of the day if not earlier). You really cannot just wander from sight to sight on a whim because of the very long ticket lines (and the possibility of a sellout while you're waiting). But it's not easy to figure out an appropriate yet efficient schedule for the various sightseeing stops so you can buy the tickets ahead of time. You have to guess whether you'll get into each sight on time (not guaranteed), how long you'll want to spend at each one, how long it will take to get to the next sight, how much of a lunch break you'll want, etc. The tickets for a lot of the sights are quite pricey; you won't want to run in and out if you're enjoying them, which argues for padding your schedule. But that means you may not cover as many ticketed sights in a day as would be possible if you could just wander around on your own schedule.

While in Barcelona you want to visit the Picasso Museum and the Sagrada Familia. Buy tickets before leaving home for the latter. You also want to take Rick Steves self-guided walking tours that are available in his Barcelona 5th edition guidebook.

Five days for Barcelona at least to see all the Gaudi sites plus Museo Miró, Muse Picasso. I can’t believe Rick Tours only give this large and important city one day.

I spent about three days in Barcelona before the tour started, and I'm glad I did. A couple more days would have added more value. I'd suggest a week, with one or two day trips outside the city.

The RS tours are well designed, at least those I've taken, but they don't pretend to cover all that's worth seeing in any city. Participants are encouraged to arrive early and/or stay on late, and given a list of worthwhile sights the tour doesn't cover. This has worked well for me and, I think, others.

Miro museum and Montjuic, Picasso museum, Sagrada Familia, Gaudí buildings in the city, Parc Guell, Barrio Gótico - these need 3 days at the very least.

I spent two days in Barcelona and felt that was not nearly enough time. It would be easy to fill five days, as well as a week. I found the DK/Eyewitness Barcelona guidebook to be very informative and would use that to supplement the Rick Steves book for a longer visit.

Dissenting voice here: while just one day is definitely not enough, I find that depending on your interests, 2 days can be adequate. 1 day focused on the Eixample (19th c. extension of the city), visiting Sagrada Familia and passing by the outside of other Gaudí buildings (tickets are expensive, lines are long). The other day focusing on the old town (Barri Gotic), making your way to Montjuic for the Miro foundation OR to the Picasso Museum if either interest you.
But this is a personal opinion. I rarely visit museums when I travel since I live in a city which is so full of them, unless they contain a type of art that I cannot find anywhere else, so I tend not to need that much time to visit a city.

One day isn't nearly enough! It takes at least 3 days to see the "top tier" sights of any major city, if that's all you're interested in doing. To really experience the city and its culture you need at least 5 days, plus time for any day trips for regional attractions. Barcelona is spectacular so don't short-change yourself if you can stay longer.

Here's my philosophy: With so many places to see, I spend more time in each city so that when I leave I feel "satisfied" and don't have a yearning to return. So, I dig down into the Tier 2 and Tier 3 attractions that interest me, will stop at a market and buy a to-go lunch to enjoy in a local park, and have an afternoon to just stroll around to take in the ambiance. Works for me!

Posting in two separate posts- we did 4 days!

Day 1:
Arrive in Barcelona at 9 am. We are taking the Aero Bus to Placa Catalunya (5.90 euro each), or a taxi is around 40 euro depending on where you go. You can take the AERO 1 or 2 - both go to Placa Catalunya. We dropped our bags off at a place near the plaza because our airbnb won't be ready for check in- website attached below - they also have changing rooms if you wanted to change before sight seeing.(https://www.barcelona-tourist-guide.com/en/transport/locker-barcelona.html).

Walk around Barrio Gotico and see the Cathedral, go La Rambla to walk around, go into La Boqueriaon La Rambla (8 min walk from Cathedral), From there walk to Placa Reial (5 min walk). Have a bite to eat and drink in Placa Reial and people watch.

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*Option to go to Montserrat if not too tired about 36 euro per person includes metro tickets there and back, funicular up the mountain, and entrance to exhibit. (https://www.barcelona-tourist-guide.com/en/tour/barcelona-montserrat.html)

La Pedrera at night (aka casa Mila). This is a Gaudi designed apartment, there is another one called Casa Batllo- I would look up each and see which you're more interested in and go to one. We had previously been to the other Gaudi house, so that’s why we chose this one. Night tickets are 34 euro, a day tour is 22 euro. At night you can go on the roof and see the different lights they put on up there and get a good view of Barcelona.
https://www.lapedrera.com/en/visits/la-pedrera-by-night/gaudi-pedrera-the-origins

Rooftop Bar: Hotel Barcelo Raval Terraza 360 (neighborhood to walk there isn't special, but the rooftop had amazing views). Metro or Uber there

Day 2:
Parc Guell to start (good to get this early if you're going in the summer because it gets hot) We are getting there right for when it opens at 8:00 am. 7.50 euro per person ticket, you choose the start time of your ticket when you buy them in advance (recommended) and you must arrive within a half hour of your scheduled time. Enjoy the park, maybe pack some sandwiches.

*optional pit stop at Hospital Sant Pau (don't need .ticket to get in) cool architecture to see and in between the two locations.

We decided to do a beach day after this, but if you are short on time, you can go to Sagrada familia after.
We took the metro to Barceloneta and walked to the water. There are a lot of people selling stuff on the beach, I would not leave belongings.

At night we are going to see a show at Palau de Musica (ours is a flamenco show but depending on the day it can be anything). The theater is beautiful - You can also just book a tour for 20 euro if you didn't want to see a show. Tickets for the show are 40 euro, but we figured its something to do at night. Just be careful when you book a seat, you want to make sure your seat has visibility of the stage (not all do!) When you click buy and click to select your seat, on the right side it says right above the price "arm chair" and "reduced visibility"/ or "no visibility" if it doesn't have a good view of the stage.

http://www.palaumusica.cat/en/programme_314?date=2018-07-06&subset=upcoming

Day 3:
Cava Winery Tour Day- We are going to get out of Barcelona and do a Cava tour (champagne of Catalunya). In Placa Catalunya there’s a Desigual store and a metro entrance right by it (it’s like behind the fountain to the right if you’re looking at the fountain). Go into the metro that way and follow signed for the Renfe Train. Take the R4 to Sant Sadurni de Anola (it’s like the 10th stop and about 45 min). On the way home you can take the R4 or the R1.

We went to CODORNÍU winery which is a bit of a walk from the train so give yourself- it was like 20 min walk). That winery is great the tour (bought tickets online before which was 16 euro per person and 90 min total) included a tasting at the end, and you take a tram ride through the huge wine cellar which was so fun! Is also the oldest family run business in Spain. I have written down the tour is only at 11:45 am or 3:30 pm so plan accordingly. Freixenet cava is a winery right outside the train station which we considered going to. We bought our train tickets that day from the machine. When we were finished we had them call us a taxi to take us back to the station. Trains back you want the line heading towards Manresa,

Dinner option Mussol Arago

Day 4:
Sagrada familia (bought tickets in advance and chose to do the nativity tower - you can pick between that or the passion tower, online reviews leaned slightly towards nativity so we picked that). Your ticket includes audio guide so pick that up first.

We then went to the Arc de Triumph and Parc de la Cituadella later that afternoon. Then we did a massage experience at Aire Barcelona.

Bars:
Rooftop bars: Hotel Barcelo Raval Terraza 360 degrees; Alaire Terr Bar

This reminds me of a backpacking trip around Europe in the early 70s. We were traveling for six weeks on a Eurail pass. When we got off the train in Barcelona I walked out of the train station, looked around and something just didn’t click for me. Didn’t even spend the night. Got back on the train and moved on. Sounds like I should give Barcelona a second chance.

It all depends on your interests. My wife and I spent 3 days there. It was actually more than enough time for what we planned to do. It was only part of a much longer trip. It would be easy to spend a few more days there.

We spent 3 days there and not nearly enough time. We saw Sagrada Familia, the Gothic Quarter, La Rambla, the cathedral and both of
Gaudi's casas. Also walked through the arch and Ciutadella park and the waterfront. Wished we had more time to see Picasso Museum, Park Guell, and the Olympic area. I would have loved two extra days! Plus the food was amazing!

Thanks for all the responses!

It may feel as if you are investing too much time in Barcelona with a minimum of four days, but please consider this is the TOP tourist destination in Europe offering a massive menu of opportunities. Peel back the layers of opportunities and be sure to book on line tickets for each opportunity. You really do not want to waste time in long lines anywhere and especially in Barcelona. What time of year are you considering?