The Draw Weight to Speed Calculator helps archers estimate the speed of their arrows based on key factors like draw weight, arrow weight, and draw length. This tool is especially useful for bowhunters, target shooters, and competitive archers who want to optimize their setup for speed and accuracy.
Using the right combination of draw weight and arrow weight ensures maximum efficiency and accuracy, helping archers fine-tune their performance. The formula used in this calculator provides a practical way to estimate arrow velocity in feet per second (fps), which is essential for making adjustments to achieve the desired trajectory and impact force.
Formula of Draw Weight To Speed Calculator
Where:
- fps = feet per second
- K = bow efficiency factor (varies by bow type)
- Compound bows: 35-45
- Recurve bows: 25-35
- Longbows: 20-30
- Draw Weight = measured in pounds (lbs)
- Arrow Weight = measured in grains (gr)
- Draw Length = measured in inches (in)
- 28 = standardized draw length
Quick Reference Table
| Draw Weight (lbs) | Arrow Weight (gr) | Draw Length (in) | Estimated Speed (fps) |
|---|---|---|---|
| 40 | 400 | 28 | 170-190 |
| 50 | 450 | 28 | 180-200 |
| 60 | 500 | 28 | 190-210 |
| 70 | 550 | 28 | 200-220 |
| 80 | 600 | 28 | 210-230 |
These values are approximations and may vary depending on bow efficiency, environmental factors, and shooting conditions.
Example of Draw Weight To Speed Calculator
Let’s say an archer is using a compound bow with the following settings:
- Draw Weight: 60 lbs
- Arrow Weight: 500 grains
- Draw Length: 28 inches
- Bow Efficiency Factor (K): 40
Using the formula:
Arrow Speed = 40 × √(60 / 500) × (28 / 28)
= 40 × √(0.12) × 1
= 40 × 0.346 = ~138.4 fps
If the draw length increases to 30 inches, the speed will increase proportionally.
Most Common FAQs
Yes, increasing the draw weight generally increases arrow speed. However, other factors like arrow weight, bow efficiency, and string type also affect speed.
Heavier arrows travel slower but retain more kinetic energy and penetrate better. Lighter arrows move faster but may lose energy quickly over distance.
The ideal draw weight depends on the game being hunted. For deer-sized animals, 40-50 lbs is usually sufficient, while larger animals like elk may require 60 lbs or more.