🎯 Ballistic Coefficient Calculator
Calculate ballistic coefficient
How to Use This Calculator
Enter Projectile Mass
Input the mass of the projectile in kilograms (kg). For bullets, typical values range from 0.005 to 0.05 kg. For arrows, use 0.0002 to 0.0005 kg.
Enter Diameter
Enter the diameter of the projectile in meters (m). Common bullet calibers: 9mm = 0.009 m, .308 = 0.00762 m. For arrows, typically 0.006 to 0.009 m.
Enter Drag Coefficient
Input the drag coefficient (C_d). Typical values: spheres = 0.47, streamlined bullets = 0.25-0.5, blunt projectiles = 0.8-1.0. The default is 0.5.
Click Calculate
Press "Calculate" to compute the ballistic coefficient, which indicates how well the projectile overcomes air resistance.
Formula
BC = m / (C_d × A)
where A = π(d/2)² = πr²
Where:
- BC = Ballistic Coefficient (kg/(m²·C_d))
- m = Projectile mass (kg)
- C_d = Drag coefficient (dimensionless)
- A = Cross-sectional area (m²)
- d = Diameter (m)
- r = Radius (m)
Example Calculation:
For a .308 bullet with mass 0.0097 kg, diameter 0.00762 m, and C_d = 0.5:
1. Calculate area: A = π × (0.00762/2)² = π × 0.01452 = 0.0000456 m²
2. Calculate BC: BC = 0.0097 / (0.5 × 0.0000456) = 0.0097 / 0.0000228 = 425.4 kg/(m²·C_d)
Higher BC values indicate better aerodynamic efficiency and less drag. High BC projectiles maintain velocity better over distance.
About Ballistic Coefficient Calculator
The Ballistic Coefficient (BC) Calculator determines a projectile's aerodynamic efficiency by calculating how well it overcomes air resistance. BC is a critical parameter for ballisticians, shooters, and engineers designing projectiles for optimal performance over long distances.
What is Ballistic Coefficient?
Ballistic coefficient is a measure of a projectile's ability to overcome air resistance in flight. It's calculated as the ratio of mass to the product of drag coefficient and cross-sectional area. Higher BC values mean the projectile maintains velocity better, experiences less drop, and is less affected by wind.
Key Factors Affecting Ballistic Coefficient
- Mass: Heavier projectiles generally have higher BC because mass appears in the numerator. More mass means more momentum to overcome air resistance.
- Diameter/Area: Smaller cross-sectional area reduces drag. This is why long, narrow projectiles (low drag) have higher BC than short, wide ones.
- Drag Coefficient: Streamlined shapes (pointed bullets, arrows) have lower C_d values (0.2-0.4) compared to blunt objects (0.8-1.0), resulting in higher BC.
- Shape: Boat-tail bullets and streamlined arrow designs significantly improve BC by reducing base drag and turbulence.
Practical Applications
- Long-Range Shooting: High BC bullets experience less drop and wind drift, making long-distance shots more accurate and predictable.
- Ballistic Trajectory Calculations: BC is essential input for ballistic calculators to predict bullet drop, wind deflection, and energy retention.
- Ammunition Selection: Compare different bullet designs to choose projectiles that best suit your shooting distance and conditions.
- Archery: Calculate arrow BC to understand how arrow design affects flight characteristics and accuracy at various ranges.
- Projectile Design: Engineers use BC calculations to optimize projectile shapes for maximum range and accuracy.
Understanding the Results
Ballistic Coefficient: Expressed in kg/(m²·C_d). Higher values indicate better aerodynamic performance. Typical ranges: handgun bullets (100-300), rifle bullets (300-800), and high-performance match bullets can exceed 1000.
Cross-Sectional Area: The frontal area that creates drag. Larger area means more air resistance, reducing BC all else being equal.
Frequently Asked Questions
What is a good ballistic coefficient?
It depends on the application. For handgun rounds, BC values of 100-200 are typical. Rifle bullets range from 300-800, with high-performance match bullets exceeding 800. The "best" BC depends on your shooting distance and accuracy requirements.
How does ballistic coefficient affect accuracy?
Higher BC improves accuracy over distance by reducing velocity loss, bullet drop, and wind drift. However, BC alone doesn't guarantee accuracy - bullet construction, consistency, and barrel twist rate also matter significantly.
Can I use this for arrows or darts?
Yes! Enter the arrow mass (in kg), diameter, and estimated drag coefficient. Arrows typically have BC values of 10-50 kg/(m²·C_d). Streamlined arrows with small vanes have higher BC than those with large fletching.
How do I find the drag coefficient for my projectile?
Drag coefficient depends on shape and velocity. Spheres = 0.47, streamlined bullets = 0.25-0.5, blunt projectiles = 0.8-1.0. For precise values, consult manufacturer specifications or use computational fluid dynamics. The default 0.5 is a reasonable estimate for most bullets.
Why is ballistic coefficient important for long-range shooting?
At long ranges, small differences in BC create significant differences in trajectory. A bullet with BC 600 will drop 50% less and drift 50% less in wind compared to one with BC 300, making hits at 1000+ yards much easier.
Does BC change with velocity?
Yes, drag coefficient (C_d) varies with velocity, especially near supersonic speeds. This calculator uses a constant C_d, which is an approximation. For precise calculations over various velocities, use specialized ballistic software that accounts for velocity-dependent drag.