Sight marks are calculated from arrow trajectory physics. Given arrow speed and sight geometry, the calculator determines how much the arrow drops at each distance due to gravity, then computes the required sight pin position to compensate. The formula uses time of flight (distance/speed) and gravitational drop (0.5 × g × t^2).
- Time of flight = distance / arrow speed
- Arrow drop = 0.5 × 9.81 × time^2 (meters)
- At 20 yards (280 fps): drop = 1.5 inches
- At 40 yards (280 fps): drop = 6.1 inches
- At 60 yards (280 fps): drop = 13.8 inches
| Distance (yards) | Drop at 250 fps | Drop at 280 fps | Drop at 310 fps |
|---|---|---|---|
| 20 | 1.9" | 1.5" | 1.2" |
| 40 | 7.7" | 6.1" | 5.0" |
| 60 | 17.3" | 13.8" | 11.2" |
| 80 | 30.7" | 24.5" | 19.9" |

