Does anyone know how many teaspoons are needed for 300g flour please?
About one teaspoon. But there is no rule. More for a quicker bread and less for slower.
The less you use the longer it takes and the tastier it is.
As Lechem said. In USA, a packet is 2 1/4 tsp and many recipes call for 1 packet for every 3-6 cups of flour. Pretty wide range. They want the consumer happy with a puffy, highly risen loaf made quickly. If you use 1/2 tsp, it will take longer to rise but be more flavorful. Depending on what your room temp is, this could be a 6-12 hour loaf-beginning to end. Yeast is more active when it is warmer.
If you want a quicker loaf today, do 1-2 tsp (or 1 packet/sachet).
Less than half a percent of the flour weight of active dry yeast so less than 1.5g (call it a gram) if instant you could start with half again. That would start to see some activity around the 90 minute mark at room temp and then hours later some significant rise. Just give an idea of the range some recipes, brioche for example call for a over full packet of even instant for that quantity (more than 7g) - it reallly depends as other members have pointed out - what kind of bread are you making ?
bread make a poolish - 50 g each flour and water and just a pinch of yeast. Let it g=ferment till it is very active and use that for your bread. A package of yeast lasts a ling tome that way and the bread is better.
I measured my yeast and its comes out to half a teaspoon for 300 grams of flour. Good Luck!
I use 1 1/4 tsp of instant yeast for 724g flour, and have been that for years. No problems. For my poolish I use 1/8 tsp yeast. That's how I make my bread, poolish then the flour, salt, yeast, water