Christmas lights

I believe a 12 x 12 dance floor accommodates 30-40 people. There are charts available online.

I have no idea on the Christmas lights, but those are probably not the ones you buy for your Christmas tree. I am sure they are much longer.

A 12x12 dance floor is pretty small and definitely not enough for 75-80 people if you expect most of them will be dancing or dancing actively.

I found this chart online with dance floor recommended sizes, but I would say these sizes are based on fairly static/slow dancing as its based on 4 square feet (a 2x2 foot area) per person, so unless everyone is moving very slowly and doesn't mind having zero personal space, you need to estimate up. A 12x12 dance floor could probably accomodate dancing by 6-10 couples comfortably at most. This website recommends 9 square feet per couple, and suggests that about 40% of your guests will be dancing. I've been to many weddings where the dance floor feels really cramped because the couples went by the recommended dance floor size based on standard estimates and in my opinion, this just doesn't work when you have a wedding smaller than 100 people because there is a certain amount of minimum space needed for the dance floor to feel inviting. For reference 12x12 is about the size of a standard horse stall. If there is anything pushed up close to the dance floor (wall on any side, tables close by) this feels very cramped and claustrophobic. You can probably get away with 12x12 if there is at least a 2-3 foot buffer on all sides of the dance floor to give the illusion of more space. I think the space allocated for dancing needs to be a minimum of 15x15 to encourage dancing, even at a smaller wedding.

View Quoted Comment I agree with this. 12 x 12 is the average size of a standard bedroom without any furniture. You can fit about 10-12 couples. I have attended many weddings with dancing where the maximum available space for dancing (they didn’t move tables away) was 8x12 and there was anywhere between 5 and 40 guests at any given time and no one felt crowded enough to make the space bigger. In a pandemic obviously you want more space.

As far as the number of light strings you will need the main thing you need to look at when buying them is how long they are. There are so many different lengths that depending on what length you decide to buy will determine how many you need. If I had to guess I would say theres about 30 stripes going across the dance floor in you picture. Something else to consider is what will you use/how will you support the middle of the light strings to keep them high and not hanging down in the way. It is extremely difficult to pull them tight enough to get little to no sag without a support in the middle. Hope that helps.