It’s been a while since you used a particular mould & you cannot remember how much product it holds & of course the note you made to remind you is in that ‘safe place’ & you don’t want to waste product, the simplest way is to melt your plain wax or soap base, add to the mould & leave to set, then pop out & weigh & the product can be melted again to re-use.
You can also pop your mould onto scales & fill the mould with water, this will give an approximate weight but please do remember that different products have varying densities & this can affect the weight of product required but as an approximate indicator water is a good one.
Many moulds are advertised as a being suitable to create a candle but when you receive them there is no hole in which to pass the wick through. The main reason for this is due to the variety of uses for the same mould.
It is a relatively simple procedure to place a hole in the mould.
Firstly you need to decide where you prefer to locate the hole.
A tapestry or darning needle, something similar in size to the wick can be used to make the hole, a pair of long nosed pliers to help pull the needle &/or wick through the hole & a length of candle wick.
You may need to place a piece of tape over the wick to help to seal the hole, to avoid wax seepage.
Now you have turned a silicone mould into a candle mould.