How Can I calculate the sales commission for new employee in new startup company?

Dear 

as a new startup you should have already a clear plan of your forecasted sales witch is an indication should be affected by the cost plan you already had set 

for the sales commission should be assigned in alignment with your plan, as it for sure should engorge your sales team to do their best but also focus on your plan and see the projection of the commission system on your initial financial plan