This is not at all obvious actually, as ideally once the mould is lined it should only stick out about 1cm.
![pie dough sticking out of the pan](/images/recettes/trucs_astuces/comment/1015-4.webp)
You can of course use your own judgement, but at home I often use a 22 cm diameter (the small one), or sometimes 26 (the large one), and in any case I always get a 300 gr cake. And of course sometimes the big one is good, and sometimes the small one is too much. Well, it's not a tragedy either, if I have extra dough, I take advantage of it to make a few more tarts and it's fine.
![excess pastry pie](/images/recettes/trucs_astuces/comment/1015-5.webp)
By the way, if it's shortcrust pastry, there will never be any excess pastry, because it will be eaten, as soon as my back is turned, by the raw pastry aficionados I have at home...
Well, it's not all that, but can we do a little better than au pif? Yes, it's a pastry chef's trick, this weight of dough thing, and as they are people of numbers, of rigour, of precision, of grams and degrees, they have invented a kind of magic formula for that, linked to the diameter of your mould. It looks like this:
Weight of dough needed (gr) = diameter of the mould (mm) + 20.
For example, you have a 22 cm mould => 220 mm + 20 = 240 => you need 240 gr of batter.
Another example, 26 cm mould => 260 mm + 20 = 280 => you need 280 gr of batter.
![plum tart](/images/recettes/desserts/tartes/278-0.webp)
Very simple, isn't it? Well, be careful we're only one cow away anyway, and if you're not comfortable with a rolling pin to roll out the dough feel free to increase the magic number, and go from 20 to 30, or even 40.
In summary: To determine the right weight of pastry you need with your tart tin, you can apply the "magic" formula: pastry weight in gr = tin diameter in mm + 20.