The following numbers may be helpful to you. Maybe some of you can extend what I've got here. It isn't meant as a formula. In fact, you'll find a lot of diversity. I found these numbers very liberating as I'm less concerned about trying to fit a round peg (my story) into a square hole. I started with the numbers from here and did a couple of calculations of my own. I assumed a 70,000 word novel with 17,500 words in the 1st act, 35,000 words in the 2nd act, and 17,500 words in the 3rd act. The Fault in Our Stars 1st act / scene length 2597/ 7 scenes 2nd Act/ scene length 750 / 47 scenes 3rd Act/scene length 750 /23 scenes Sole Survivor 1st Act / scene length 1235 / 14 scenes 2nd Act / scene length 1330 / 26 scenes 3rd Act / scene length 1140/ 15 scenes The Runaway Jury 1st Act / Scene Length 1650/11 scenes 2nd Act / scene length 750/ 47 scenes 3rd Act / scene length 600/ 29 scenes
It is writing not bloody sheet music! Sit down a moment before you hurt yourself. Just let it flow naturally, stories decide when they are done not your math and order. You need to just write it and then trim the fat. Otherwise you will have all kinds of chaos, and for you that might wind you up a bit. So take a step back, breath, and make the magic happen.