Arrow Speed Calculator

How Is Arrow Speed Estimated?

Arrow speed depends on how much energy the bow stores in the drawn string and how much mass the arrow carries. A heavier arrow leaves the bow slower; higher draw weight and longer draw length increase speed. This calculator uses a physics-based energy estimate in imperial units.

Arrow Speed Formula

\(F\) is peak draw weight in pounds-force, \(d\) is draw length in inches, \(g = 32.174\,\text{ft/s}^2\), and \(m_{grains}\) is arrow mass in grains. The factor \(7000/12\) converts lbf·in of stored energy and grain mass into feet per second.

Example: 70 lbf draw, 28 in draw length, and 400 grain arrow gives about 429 fps in this ideal model. Real bows transfer less than 100% of stored energy because of string mass, limb efficiency, and damping.

Factors That Change Real-World Speed

IBO bow ratings use standardized conditions: 30 in draw, 70 lbf, and 350 grain arrow. Actual speed also depends on string weight, cam design, brace height, and arrow spine. Use this estimate for quick comparisons, then confirm with a chronograph when tuning equipment.