Enter your rocket's Center of Gravity (CG), Center of Pressure (CP), and body diameter. Get stability margin in calibers with an instant safe/marginal/unstable assessment.
Stability margin is expressed in calibers — multiples of the rocket's body diameter. A 2.6-inch diameter rocket with CG 3.9 inches ahead of CP has 1.5 calibers of stability margin. The minimum safe margin is generally 1.0 caliber. Most well-designed rockets fly at 1.5–2.5 calibers. Above 3.0 calibers, over-stability causes excessive weathercocking in crosswinds. CP must be determined using Barrowman equations or flight simulation software (OpenRocket, RASAero) — this calculator does not compute CP, it evaluates the margin from your CP input.