# Arrow Speed Calculator

This calculator is based on average efficiency gains as arrow weight is increased from 5 grains per pound (IBO).  The most critical factor is the IBO speed entered as this is the starting point of the calculations.

Most IBO ratings are not real world numbers. In the majority of cases once a peep is added the speed will only be a few fps off but the rating of some bows are significantly off to begin with. I set this calculator up assuming a standard peep. If your peep is significantly heavier than normal or you have a bunch of other stuff on your string then that will be causing your base rating to decrease.

Also, every bow gains efficiency a little differently. The worse the bows efficiency at IBO the more growth it will see as arrow weight increases. I created an average efficiency curve based off of bows from APA, Elite, Bowtech, Hoyt, and PSE ranging from 40lbs up to 85lbs. This average will get most bows fairly close but if your bow is on the far end of the efficiency spectrum then it will be off a bit.

The upside is that even if it's off due to this the numbers should be much closer than any of the other calculators out there. That was the main goal of this project.

For the most accurate results it is best to use a known speed and arrow weight under 6 grain per pound to fine tune where your base IBO should be.

Example - A 70#/29" bow that's rated at 350 fps is has been chronographed at 315 fps with a 400 grain arrow.  At the rated 350 fps IBO the speed should be 319 so we know that the IBO is slightly high.  Reduce the IBO speed until the calculator shows the verified speed of 315; in this case the correct IBO value would be 346 fps

IBO Speed

(feet per second)

Draw Weight

(pounds)

Draw Length

(inches)

Arrow Weight

(grains)

Calculated Arrow Speed

0

Kinetic Energy

0

Momentum

0