Here’s a cheat many pro bakers use: freeze the stick for 10 minutes. Then use a cheese grater to shred what looks like a 1/4 cup pile.
Or, just buy butter sticks already marked with cups and tablespoons. They exist. They’re your best friend.
But honestly? The real answer is: half a stick. Forever and ever. Amen. Now go make something delicious, and don’t forget to lick the knife.