Calculating Arrow Speed Formulas

There are a number of arrow speed formulas out there for people who want to try and calculate mathematically how fast their arrows are going in fps (Feet Per Second).

Sadly they are all inaccurate.

My advice? Calculate your arrow speed using multiple different formulas and then get a range of numbers or average number. Then you will know roughly how fast your arrows are going.

In which case you are also going to need to know the meanings of some words and acronyms...

IBO (International Bowhunters Organization number used as a measurement for calculating arrow speed, based on a 70 lb bow. The arrow will have a grain weight of 540 [9 grains of arrow weight per pound of bow weight]. The draw length will be set at 30 inches. The chronograph used for measuring the speed will be placed at point blank range for testing.)

AMO (Archery Manufacturing Organization number used as a measurement for calculating arrow speed, based on a 60 lb bow. The arrow will have a grain weight of 350 [5 grains of arrow weight per pound of bow weight]. The draw length will be set at 30 inches. The chronograph used for measuring the speed will be placed at point blank range for testing.)

DRAW (The distance you pull back the arrow from the arrow rest.)

GRAINS (A weight measurement for arrows and arrowheads. 7000 grains is 1 pound.)

STRING WEIGHT (Any added weight on the bowstring will slow your arrow down. Dampeners and similar devices will weigh down your bowstring.)

Once you know most of these numbers you can try and calculate FPS (Feet Per Second) using the different formulas. Try using the IBO formula and then the AMO formula and see the different results. Neither will be truly accurate to your actual arrow speed, but the average should be reasonably close.

There is also the ATA (Archery Trade Association) formula, which has gained some popularity despite being more restrictive in its calculations.

NOTE

If you really want to know the specific number then you will need to buy a gadget and then use it several times to try and get an average number based on the readings.

eg. 3 consecutive readings might be 139 fps, 138 fps and 140 fps = averaging 139 fps.

2nd NOTE

For those of you who are into hunting please note that arrow speed doesn't matter so much when it comes to hunting. Yes, light arrows are faster. But HEAVY arrows do more damage because they have more momentum and impact.