I would use the visual art composition "rule of thirds" here and push it a bit further to say 750/400. Theory would say this will be more pleasing to the eye. There is plenty of info on the net about it. Good luck!

Find your basin first, and then calculate the height based on the height of the people in your house. (excluding the kids, they will grow). Rule of thumb is convenience of use and ability to look in the mirror without tiptoeing or bending down. Top of basin is usually 90cm (approx) for a above bench vanity, the table needs to be lowered. for a flush mount / undermount, then the bench will be at 90cm. My daughter is 150cm now, and 90cm benchtop works ok for her.

even if the tiles lined up exactly with the top of the cabinet if the cabinet sticks out from the wall (as apposed to being recessed inside the wall) the top of the cabinet will look higher when viewed from your lower viewpoint.....if you like the cabinet keep the taller cabinet and the difference in height will add interest to the look of the room but you may also find that the top of the windows and doors are not exactly the same (allowing for architraves and thickness of frames) so you could tile to a line below the lowest door or window height so that the tiles are the same height all around the room and the other variations will add interest

Hi Renata, from a Kitchen designers perspective it is not just about access or reach. Foshan Yubang is correct and it all depends on the style of your kitchen and the end look that you are after. Door and window heights in most basic spec homes are a standard 2100mm high and the old thinking was to pick up this 2100mm room line with your tall kitchen cabinets but things have changed. If you are building a modern / contemporary home with 2700mm high ceilings and using large tall glass windows and tall sliding glass doors then a modern style 2100mm high kitchen will look quite squat, even with a standard style bulkhead. Modern Style Kitchen trends also tend to have single line overheads (not stepped) sitting above 700mm high splashbacks and so with 2100mm high cabinets this makes the overheads only around 480mm high and again making the kitchen look squat compared to going all the way up to the ceiling and finishing with a shadow mould and having larger overheads or even just going up to 2400mm high which you then have around 780mm high overheads that again makes your kitchen look better balanced in a tall room. A good example of this is actually Dreamers image above where this kitchen is modern in style, has around 700mm high splashbacks around 2400mm high tall cabinetry (not 2100mm) with around 750mm - 780mm high overheads and a stepped out bulkhead that is around 200mm high (not 600mm high) and square set to the ceiling. It all depends on the style of your kitchen and how you want it to look, perhaps start looking at lots of kitchen photos to pin down how you want your kitchen to look and then decide from there. I would suggest though that if you are lucky enough to have the extra height, then to use it. Hope this helps, Malcolm