Sourdough calculator

There are plenty of technical scientific papers out there that show how the main components of sourdough cultures respond to temperatures, but there's not an easy formula that will distill this down to a simple calculation. The problem is that feeding schedule can depend a lot on the hydration level of your starter (i.e., how much water per how much flour), the type of flour used for feeding, the unique microorganisms in your particular starter, etc.

Since you apparently haven't worked much with sourdough yet, you should know that 10 degrees Celsius is a bit low for more sourdough cultures to function continuously. Instead, most bakers will bring their sourdough up to room temperature (around 20-25C) for feedings periodically. Bakers who make bread on a daily basis may not even refrigerate their starter at all, merely feeding it each day to prepare the preferment for the next batch of bread on the following day. Those who bake on a less frequent basis will use a cooler storage location, generally bringing the sourdough culture up to temperature for feeding and growth before mixing a batch.

All of that said, it is possible to grow sourdough starters at a constant 10C range, but in that temperature range, you tend to risk producing a more sour flavor (as the lactic acid bacteria that produce the sour flavor will grow better than yeast at such low temperatures). That can be mitigated somewhat by using a very low hydration firm dough and diluting the starter culture with multiple feedings to build up a final dough, but that's rather complicated and time-intensive for someone just starting out.

Instead, to start I'd recommend instead bringing your sourdough up to room temperature, feeding and growing a bit, then removing what you need for a batch of bread, and storing the rest at a cooler temperature until you need to feed it and bake some more.

Edit: From a comment, I remembered that it is possible to maintain a starter continuously even under refrigeration. I don't know much about that process, though I remember seeing such techniques mentioned. Most standard sourdough starter feeding techniques I know of usually involve removing the starter from the fridge, feeding, then leaving the starter at room temperature for at least a couple hours before returning to the fridge. In my experience, it does lead to stronger yeast growth to do so, but perhaps those with more experience keeping starters continuously at cold temperatures can give better answers.