A kitchen scale is always recommended when it comes to baking. This is because many ingredients' volume can change depending on temperature, type and other factors. For example, your starter will be a lot more voluminous when it's active.
Here are some approximate volume to weight conversions I made for anyone who can't get their hands on a scale.
|Starter (100% hydration, pre-feed)||1 tbsp||26g|
|Flour||1 cup||130 - 150g|
|Water (room temp)||1 cup||226g|