Kinetic energy
How much energy the arrow carries. Heavier and faster means more. Speed should come from a chronograph — speed at the bow is not speed downrange.
Calculator
Use a chronograph reading. Drag slows the arrow after it leaves the bow.
69.96 ft·lbf·94.82 J
350.0 gr (22.68 g) at 300.0 fps (91.4 m/s)
How it works
Kinetic energy is the energy of motion. Both the imperial and SI formulas describe the same arrow; this page shows both so you can compare setups without converting by hand.
Enter total arrow weight (shaft, point, insert, nock, and fletching) and a chronograph speed.
Formula
KE (ft·lbf) = grains × fps² / 450,240 KE (J) = ½ · m(kg) · v(m/s)² Momentum (slug·ft/s) = grains × fps / 225,218
Worked example
350 grains at 300 fps is about 69.96 ft·lbf (94.82 J), with momentum about 0.466 slug·ft/s.
FAQ
Why both units? Clubs and manufacturers mix grains/fps with grams and joules. The two energies are the same quantity.
Is this a hunting legal check? No. Some places set minimum energy rules; this page only reports the physics.