I have a float value between 0 and 1. I need to convert it with -120 to 80. To do this, first I multiply with 200 after 120 subtract. When subtract is made I had rounding error. Let's look my example. float val = 0.6050f; val *= 200.f; Now val is 121.0 as I expected. val -= 120.0f; Now val is 0.99999992 I thought maybe I can avoid this problem with multiplication and division. float val = 0.6050f; val *= 200.f; val *= 100.f; val -= 12000.0f; val /= 100.f; But it didn't help. I have still 0.99 on my hand. Is there a solution for it? Edit: After with detailed logging, I understand there is no problem with this part of code. Before my log shows me "0.605", after I had detailed log and I saw "0.60499995946884155273437500000000000000000000000000" the problem is in different place.