Crossbow users are always adjusting their arrow weights to get that “Perfect Setup”, but at the same time are worried about what is going to happen to their initial speed.
This calculator is designed to help with that.
There are different thoughts about how much weight change results in a 1 fps change in speed, this calculator is based on a rule of thumb that for every 5-grain change there will be a 1 fps change in speed. We know that not all bows/arrows will react the same, that is way you can select 1 - 5 grains for every 1 fps change.
Every bow is different and a change in any weight may result in a different speed change. I.E. a 3-grain change with one bow/arrow combo could be the same a 2-grain change with an different bow/arrow combo.
Use the calculations to get an idea of what may happen with your bow/arrow combo.