Personally, I would center it from the cabinet edge. I like visual symmetry. But, I think that is a personal preference. Not sure how your base cabinet is structured, but if it consists of cabinets and drawers that may also affect the sink placement. Maybe pictures of the type of vanity would help if you have them.

I like the lights centered over or around the mirror, which is what I look at whilst shaving, brushing my hair, or other grooming and I need to see clearly, which is accomplished by having light hit my face from several directions. That's usually also centered on the sink, but if it's off-center, I'd position the lights wherever you tend to stand when you make up.

I probably would have centered the sink in the 54" inches between the upper and the edge but I don't think it's a huge deal that it's centered on the entire width. I think it's more important that the sink, mirror and lights are all centered to one another.

I think in all those pictures the sink is centered in the sink base cabinet. So, I would think your cabinet layout may really be the deciding factor.

Here is one more picture with the sink and mirror centered on a cabinet, and probably the wall, but definitely not centered on the space framed by the tower:

[Traditional Bathroom[(https://www.houzz.com/photos/traditional-bathroom-ideas-phbr1-bp~t_712~s_2107) by Portland Kitchen And Bath Kirstin Havnaer, Hearthstone Interior Design, LLC

and another centered on the cabinet

[Traditional Bathroom[(https://www.houzz.com/photos/traditional-bathroom-ideas-phbr1-bp~t_712~s_2107) by Austin Interior Designer Laura Britt Design

TSG1104 is right - the cabinet layout is the key to it looking purposeful and not cockeyed

(fingers crossed that everything is ok)

Here is my preliminary drawings for my new bathroom. I suppose the centering would depend on your needs such as a long countertop on one side of the vanity. Also the style. I have chosen to center the sink at the portion that is left over after the tower is in place.

Have you chosen a vanity yet? As others have pointed out, the sink placement is often determined by your base cabinets, unless you have a vanity where the whole top 'drawer' space is blind, ie not used for actual drawers. I like to have a certain amount of useable space at least on one side, for drying sweaters, changing babies, whatever..., so think about how you plan to use that 54" of space.

I'm sort of surprised that the plumbing and electrical have already been put in without having the vanity there. I'm not clear about whether you have chosen a vanity that just hasn't arrived yet, in which case, I'm going to assume that the sink is centered on the 72" dimension.

Hi raehelen! No the vanity hasn't arrived yet. They had the ligting and the plumbing centered in the 72 inch vanity space. I'm beginning to think I shouldn't have that cabinet on top of the vanity to the right. Because if I center the sink and light in the 54' space then it will be off kilter from the cabinets and then that will look funny won't it? He's ordered the vanity cabinets already and it will be three cabinets with a drawer on top with the middle drawer being just a drawer front. If the sink and lights are moved center of 54 inch space then that won't align with the middle cabinet. Which is better OR should I just do away with the cabinet on top. My contractor is actually away for several days as he is having a minor surgery the rest of this week. Boy is this stressing me out! Stuff I hadn't thought about and wish the contractor had! Thanks everyone for your posts. What do you all think I should do?

can you post an image or a link to the vanity?

Maybe I'm not visualizing it correctly, but if you only have one cabinet with a drawer front then that is where the sink has to go.

If you need the cabinet for storage, then i would use it. Even though my preference would be to center it off the cabinet. If I couldn't do that, I would take centering it off the vanity to giving up storage. My guess is no one else will ever give it a second thought.

I think Treasure's pics really help. I need a visual to help me figure things out! I would look up on Houzz and go through tons of pics to get a feel for how it's going to look. I don't think having the sink centered on the 72" vanity is necessarily a mistake. I am planning a similar arrangement in my next bath reno, and now you've got me thinking... though I am just doing a tower, no counter on that 18" section, I was going to centre it, but now am remembering that when we built our previous house when I had a baby (oh to be young again...literally built the house with baby in playpen!), I had the main BR sink off centre to allow room for changing/bathing etc. Perhaps I should do that again, this time for grandchildren (may happen one day...) or for future resale. But, when the sink is off-centre to the remaining 54", mirror/medicine cabinet placement becomes trickier. My old BR was done in the days of big sheet of glass and theatre style of strip of bulbs over the mirror, so it wasn't an issue. Do you know what you are doing for mirror and lighting?

Hi! Enduring, I don't have a visual because I don't have the vanity yet. Raehelen, The mirror that I previously had covered the whole vanity and my plan is to cut It down and have if framed. I was going to have it framed be to go over the 54 inch countertop space. My lighting is a 3 light golden bronze vanity light to go over top the mirror. As for the vanity, My contractor has divided the 72 inch space into 3 cabinets with a drawer above each cabinet. The middle drawer will be for show only. I had originally wanted drawers on either side instead of cabinet but my contractor talked me into all cabinets below the drawers then we will have pull out shelving. So the sink has to be centered over the middle cabinet. I'm thinking the best thing might be to do away with the countertop tower. He has special ordered everything already . I wish I had thought about all this when we talked about it in the planning stages. If I keep the countertop cabinet and keep placement of sink in the middle of the vanity, then I'm not sure how to do the mirror. Because the vanity area is on the narrow side, I wanted to keep the large mirror to make the room look larger. Wish I could have affordered to hired a designer. Its amazing what you don't think about before hand. I so...appreciate all of your suggestions and help! This is such a great community of people!

Most definitely center the sink in the middle section of the vanity - with or without the tower.

If you keep the tower (I think I would, but would have to see it first) you can visally balance the other side with some tall candles, flowers, apothecary jars filled with pretty bath salts, seashells, whatever works in your space. You could also use a tall wine rack filled with rolled towels:
see link below

If the planned tower is just too big, maybe you can add storage with smaller floating shelves or wall mounted cubbies on either side of the sink/mirror:
see picture from Beauty 4 Ashes

Here is a link that might be useful: wine rack for towels and other bathroom storage ideas