Arrow Speed Calculator
Calculate arrow speed, kinetic energy, and momentum for archery and bowhunting
Arrow speed is calculated using a formula that takes into account the bow's draw weight, draw length, and the arrow's weight. The basic formula is:
Speed (FPS) ≈ √((2 × Draw Weight × Draw Length) / Arrow Weight) × 10
Where:
- Speed is measured in feet per second (FPS)
- Draw Weight is in pounds (lbs)
- Draw Length is in inches
- Arrow Weight is in grains (1 grain = 1/7000 pound)
- Draw Weight: Higher draw weight generally results in faster arrow speeds, as more energy is stored in the bow.
- Draw Length: A longer draw length increases arrow speed by allowing more time for energy transfer from the bow to the arrow.
- Arrow Weight: Lighter arrows travel faster but carry less momentum, while heavier arrows are slower but maintain more energy downrange.
- Bow Efficiency: The bow's design and quality affect how efficiently it converts stored energy into arrow speed.
Kinetic energy (KE) represents the energy an arrow carries in flight. It's calculated using the formula:
KE = ½ × mass × velocity²
For hunting applications, kinetic energy is crucial as it indicates the arrow's potential penetration power:
- 25-41 ft-lbs: Suitable for small game
- 42-65 ft-lbs: Appropriate for medium game
- ≥ 65 ft-lbs: Adequate for large game
Momentum is the product of an arrow's mass and velocity. It's important because it indicates the arrow's ability to maintain its trajectory and penetrate targets. The formula is:
Momentum = mass × velocity
Higher momentum values generally indicate better penetration potential and resistance to wind deflection. This is particularly important for:
- Long-distance shooting
- Hunting large game
- Shooting in windy conditions
- Achieving consistent accuracy
What is a good arrow speed for hunting?
For hunting, arrow speeds between 270-300 FPS are generally considered optimal, balancing speed with accuracy and penetration. However, speeds as low as 230 FPS can be effective with proper setup and shot placement.
How does arrow weight affect speed?
Lighter arrows travel faster but lose energy more quickly and are more affected by wind. Heavier arrows are slower but maintain energy better and provide deeper penetration. Most archers find a balance between 350-500 grains for hunting arrows.
Can increasing draw weight always increase arrow speed?
While higher draw weights generally produce faster arrow speeds, there's a point of diminishing returns. It's important to use a draw weight you can handle comfortably and consistently, as proper form is more important than maximum speed.