Grain per Inch (GPI)

GPI stands for Grains Per Inch and indicates how much an arrow shaft weighs per inch of length. It therefore describes the base weight of the shaft without the point, nock, or fletchings. A shaft with 8.5 GPI has a shaft weight of 238 grains at a length of 28 inches (8.5 × 28).

Why is GPI important?

  • Higher GPI = more mass, often resulting in a smoother, more stable flight
  • Determines the total arrow weight
  • Influences speed and energy
  • Affects FOC and tuning
  • Lower GPI = a faster arrow
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