Tomatoes in planters

Hi, Wonder if anyone has a strong view on the width and depth needed to do tomatoes in planters on a patio. I guess growbags set a subconscious min width (and depth???  ) but wondered if there was any advice regarding dimensions. Haven't decided on varieties yet and I'll be building the planters myself

we use builders buckets for tomato plants in the greenhouse

I do the same and they work well, but if you are building them yourself, I would suggest making them a bit bigger and setting a plastic tray in the base.  You can put your drainage holes just above this on the sides.  Then you will have a reservoir you can fill with gravel that will help with watering and also keeping your toms upright in windy weather.