Ballistic Coefficient Calculator
Calculate ballistic coefficient (BC) from bullet weight, diameter, and drag model. Compare G1 and G7 BC for long-range shooting trajectory.
Specialist tool for Archery1 documented formula2 real workflowsPrivate in your browser
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Inputs that matter
Bullet Weight, Muzzle Velocity, Velocity at Distance, Distance, and 1 more
Output to expect
Ballistic Coefficient Calculator
How it works
1 documented formula across 1 calculation mode
- Keep 5 bounded inputs within the limits shown beside the fields.
- Confirm that every value uses the unit and time basis shown before comparing scenarios.
- Change one input at a time to see which assumption materially changes the result.
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Reference & details
How it works
Updated July 2026
How it works
Updated July 2026BC Definition
BC = SD / i where SD is sectional density (weight/area) and i is form factor vs the standard projectile (G1 or G7 reference). Higher BC retains velocity better downrange.
BC = SD / form factor; SD = weight (lb) / diameter² (in)G1 vs G7 Drag Models
G1 uses a flat-base reference — common in hunting ammo catalogs. G7 uses a boat-tail reference — more accurate for modern long-range bullets. G7 BC is typically 0.5–0.6 of G1 for same bullet.
BC_G7 ≈ BC_G1 × 0.55 (approximate conversion for boat-tails)Form Factor from Geometry
Form factor derives from ogive radius, boat-tail angle, and meplat diameter relative to caliber. Long ogive and boat-tail reduce form factor, increasing BC.
i = form factor from bullet profile vs G7 standardUpdated: July 2026
Example Scenarios
Convert to G7: ~0.462 × 0.55 ≈ 0.254 G7 BC for Strelok or Applied Ballistics solver. Use G7 for trajectories beyond 600 yards.
105 gr .243 (SD 0.252) vs 175 gr .308 (SD 0.264). Similar SD but .308 boat-tail may have higher BC due to better form factor at same SD.
Chronograph at muzzle and 500 yards; solver back-calculates BC. Published BC may vary ±5% from your rifle's actual muzzle velocity and atmospheric conditions.
Common Mistakes to Avoid
Common Mistakes to Avoid
Entering G1 BC into a G7-based ballistic solver
G1 and G7 are different drag models — using G1 BC in G7 software causes significant elevation errors past 600 yards. Convert or use matching model.
Assuming published BC applies at all velocities
BC drops through the transonic zone. Long-range solvers use velocity-dependent BC curves (multiple BC values) for accuracy past 800 yards.
FAQ
G7 BC above 0.250 is solid for 1000-yard work. Elite LR bullets exceed G7 0.320. Hunting bullets typically G7 0.150–0.220 — adequate to 400–600 yards.
Use G7 for boat-tail match bullets — more accurate beyond 600 yards. G1 works for flat-base hunting bullets at shorter range. Never mix G1 BC with G7 drag model.
Yes — BC varies with Mach number (transonic effects). Manufacturers publish average BC over a velocity range. Transonic zone (Mach 0.9–1.1) shows BC instability.
BC is a bullet property, but air density at altitude reduces drag. Trajectory solvers adjust for density altitude — BC value stays the same, drop decreases at high elevation.
Approximate BC from sectional density and estimated form factor. For precision, use manufacturer data or Doppler radar-derived BC from lab testing.
About Ballistic Coefficient Calculator
Ballistic coefficient (BC) measures a bullet's ability to overcome air resistance compared to a standard reference shape. This calculator estimates or converts BC from bullet dimensions, weight, and drag model for trajectory software.