My kitchen is almost the same size; but didn't have as large a window & has a notch out of one corner for the basement steps (so smaller functional space). But also white cabinets & white floor.

I had just 2 round fluorescent fixtures (no under cabinet lighting) and that was never enough light; not bright enough and not in the right places. .

I put in 5 LED disc lights and that seems to be more that I needed. Each one is brighter than the lights I replaced (each 800 lumens) and I think that only 3 would have been enough.

So it will depend on the bulbs that you plan to use (LED vs CFL) and the size and capacity of the fixtures that you choose, whether 2 or 3, but I don't think one will be enough. Three smaller fixtures or 2 larger ones?

I think there is a thread on the lighting forum about how to calculate how many lumens you need for a given square footage.

I have a kitchen that is 13 X 13 and I have 5 or 6 canned lights, UCL, a pendant over my sink and one over my island. I LOVE working in my kitchen now because I can actually see what I am doing. It is better to have lighting that you don't need than to not have lighting that you do need. I thought maybe all my lighting was overkill but I use all of it and many times have it all on at the same time.

I went and found the thread in the lighting forum, and it recommends 35 lumens/sf. So I need ~4000 lumens. 1 60 watt bulb is 800 lumens, so I need 5 60 watt bulbs worth of light. I'm looking at a fixture with 2 60 watters, so I need 2 1/2 of them. Hmmm....

Does undercabinet lighting get counted in the mix?

Weedy - layered lighting is great - and I say - you can never have too much light in the kitchen as long as you have switches and dimmers.

Our kitchen isn't quite a galley - but I think around 11x17.
I put in 2 decorative flush mount lights - 4x60
Then, I have lots of cans around(7 and wish I had put 1-2 more in) and each is equiv to 100 W but they are LED.
Then, I have my UCL.

I love all of the light when I need it!

I'm finalizing our lighting plan right now and struggling with how much is "enough" light.

What we are leaning toward is "overlighting" and then cutting that back with dimmers. Lighting is always so much more difficult to do right later...so, we want to get it right the first time. My mom has vision issues...she's always complaining about how their house doesn't have enough light and like it or not, I'm not getting any younger...as I get older, getting enough light is likely to be more important, so we're trying to get enough light right off.

How many lighting fixtures you'll need depends on a number of factors.
Ceiling height, cabinet layout, fixture type and size all play into your final design.
In our 8'x12' kitchen, for example. we have 12 3" 50w MR16 recessed cans and under cabinet lighting.
That's a lot of fixtures for a small space, and it's enough, but just barely.
In fact, I'm looking into changing the bulbs to LED retrofits to see if it will help.
You may be best off posting your layout, including dimensions, on the lighting forum.
The folks over there are very knowledgeable and helpful.

One thing that might be confusing (is to me at least), basing the lumens needed on the overall kitchen dimensions. I wonder if the space on the one wall taken up by cabinets, pantry and frig should have been deducted? Because there really isn't any floor/ceiling/counter/wall to illuminate in that area. But I am pretty sure that you do count counter area even though there are also cabinets-- you want to illuminate the interior of the cabinets a bit when opened also.

But yes, you do count any oversink light and UCLs in the total lumens.

Based on that calculation, I did overdo it -- I could have eliminated 2 of the ceiling cans.

I did install a dimmer after I saw all the brightness.

I made sure I had 35 lumens/sq ft in just the recessed/pendants - 6 recessed + 2 pendants in 8 x 15 galley. UCL and hood light are extra for me. It's not too much. Mine is all LED (except the hood, and that will be changed out soon.) An electrician told me recently that something people don't realize is that LEDs lose some brightness as they age. So I'd err on the side of extra light, especially if you have it on a dimmer anyway.

I put 7 pot lights in the cooking area & 2 hanging thin ones over my island. Should I do pot lights in the cooking area also or just a fixture over table or both?

Sorry, I mean eating area, what should I do?