A 1:16 ratio is an easy starting point for filter coffee: use 15 g of coffee for 240 g of water. Aim for water around 92 to 96 °C and pour slowly in a few stages.
Tastes too light? Add a little more coffee or grind finer. Too strong or bitter? Add water or grind coarser. The ratio is a starting point, not a rule carved in stone.
Weigh the coffee and water if you can, but keep it simple. A consistent, enjoyable cup is already a win.