How many days needed for Madrid?

Segovia is a good day trip. The Roman aquaduct there is a marvel to anyone. I liked my day trip experience there better than the Toledo one,

I think 3 days is enough in Madrid not unless you find a lot of pleasure in taking time in the museums there looking at master works in European painting.
But just a tip: you will get more out of the time you spend in a place seeing and doing things you discover yourself from your own research in guide books.

It depends on your priorities. On both my visits, I've allowed a full day for the Prado. Others are more than satisfied with a couple hours there. You don't need to plan in advance for a day trip to Segovia, so you can decide once you've had a look around Madrid.

Arrival (Half) Day
(??) 2pm...Reina Sofia Museum (quick look at Guernica)
4pm...Stroll thru Retiro Park
6pm...Drinks at Mercado San Miguel

Full Day
10am...Royal Palace
12pm...City Walk

Plaza de Oriente
Plaza Mayor
Puerta del Sol
Metropolis Bldg
Plaza de Cibeles
Puerta del Alcala

2pm...Lunch in the Salamanca district
4pm...Prado Museum
8pm...Dinner on Plaza Santa Ana

It depends upon your interests, but for me Madrid is a much underrated city that merits more time than many give it. My wife and I were there in 2005, and with all the day trips (Toledo, El Escorial, Toledo) we felt as if we missed Madrid even with five nights. I had visited solo in 2001 and had the chance to spend more time there. I would give Madrid two full days minimum. I am a museum nut and the Prado is an an all time favorite, but I think three or four hours was enough for me. Madrid is so much more than a museum city though,

El Escorial does often get overlooked here in favour of Toledo and Segovia. It can be visited in an afternoon and is well worth it.

Check online to be sure the parts of El Escorial you're interested in are open. Quite a bit was closed last year.

Oh I wasn’t saying it is only worth a quick look. I spent hours there.
My point was that its worth finding an hour or so to at least check out 'Guernica', the iconic work by Pablo Picasso.

Thanks for the all the input! I think we will wait until we arrive in Madrid to decide on the day trip to Segovia. It will be our last day there and we can decide once we see how much of Madrid we were able to squeeze in.

I spent 16 days in Madrid last fall. It was my 5th time visiting Madrid which one of my favorite places in all of the world. (Along with Paris, Venice, and London). I think it is beautiful and vastly underrated city filled with great museums, large and small, and with gracious people. Granted, I am one of those artsy tourists, so I went to numerous museums, big and small....most for the 3rd to 5th time.

strong textI had never been to Segovia or Avila, so I took a bus tour (Almost never do that, but the timing made it make sense, and the cost was around $100 for a very full day.).
Obviously the big museums are very worth a visit (Prado, Reina Sofia, and Thyssen-Bornemiza), But one of my favorite museums in all the world is the Museo Lazaro Galdiano. Small, easily digested collection in an early 20th century townhouse.
I was surprised to find the art works in the museums were almost all labeled in English and Spanish. The supertitles at the Teatro de la Zarzuela were also in both English amd Spanish! (That theater among others gave 50% off tickets for those over 60, but you have to show your passport.)
Couldn’t go to Madrid without flamenco and bullfights. A friend is married to a member of a flamenco family designated a “Living treasure of SPAIN,” so I took his recommendation on where to see the best flamenco in Madrid. (The Best is still probably in Andalucía.) That was the the Corral de la Moreria. Good dancing. (Show and drink or show and meal options.) I thought the show was exceptionally short (55 minutes), very few dancers, and not cheap. But the dancing is very good.
I can praise Madrid for hours. Trust your gut for what brings you pleasure. You can find it in Madrid.

Have been to the Reina Sofia a few times and generally go in the evening when the entrance is free. Love Guernica. If you decide to go to San Lorenzo del Escorial, you may as well take a couple hours and go the 8 miles to visit the Valle de los Caidos. Somber, but interesting.

I'm going to throw the Sorolla museum out there as worth a stop in Madrid if you're into art museums.

I will concur with other advocates that the city could either by 2 days of intense art museum touring, or far more than that of just enjoying neighborhood ambiance and Spanish-ness. I found Madrid to be an incredible city and it's now one of my favorite cities on earth. I've been three times and eagerly anticipate going again someday for as many days as possible.

That said, I wouldn't skip a day trip to Toledo (or even better, a dusk/evening/overnight trip)

Check the status of El Escorial before heading out there. The last time I looked, a lot of the display area was closed.