Rocket Drag Coefficient Calculator

Estimate total Cd by summing nose, body, base, fin, and interference drag using semi-empirical methods from Hoerner and Mandell/Caporaso/Bengen.

Inputs

Body diameter (mm)

Body tube length (mm)

Nose cone length (mm)

Nose type (1-3)

Number of fins

Fin root chord (mm)

Fin semi-span (mm)

Fin thickness (mm)

Flight velocity (m/s)

Surface finish (1-3)

Tab to move between fields

Results

Total Cd

0.89

Nose cone Cd0.05

Body tube Cd0.24

Base drag Cd0.14

Fin Cd0.39

Drag force at speed (N)2.31

Reynolds number2,598,895

Fineness Ratio2.76%

How to Use This Calculator

Enter Body diameter (mm), Body tube length (mm), and Nose cone length (mm).
Set Nose type (1-3), Number of fins, and Fin root chord (mm).
Adjust Fin semi-span (mm), Fin thickness (mm) as needed.
Review the Total Cd result.
Use Nose cone Cd and Body tube Cd to inform your decision.

How the result changes with Body diameter (mm)

Body diameter (mm)	Total Cd
31	0.82
106	0.29
195	0.24
270	0.22

What each input means

Body diameter (mm): Outside diameter of the body tube.
Body tube length (mm): Total length of body tube (excluding nose cone).
Nose cone length (mm): Length from nose tip to body shoulder.
Nose type (1-3): 1 = Ogive (lowest drag), 2 = Conical, 3 = Von Karman (optimal supersonic).
Number of fins: Number of fins. Fewer fins = less drag.
Fin root chord (mm): Length of fin at the body tube.
Fin semi-span (mm): Distance from body tube to fin tip.
Fin thickness (mm): Thickness of fin stock material.
Flight velocity (m/s): Velocity for drag force calculation. Use expected max velocity.
Surface finish (1-3): 1 = Smooth (polished/painted), 2 = Typical (painted), 3 = Rough (unpainted cardboard).

What each result means

Total Cd: Total drag coefficient referenced to body cross-section area. Typical rockets: 0.3-0.8.
Nose cone Cd: Drag contribution from the nose cone (pressure + friction).
Body tube Cd: Skin friction drag from the body tube.
Base drag Cd: Drag from the blunt base (wake pressure).
Fin Cd: Combined fin friction and pressure drag.
Drag force at speed (N): Total aerodynamic drag force at the specified velocity.
Reynolds number: Flow regime indicator. Most model rockets operate in turbulent flow (Re > 500,000).

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Body diameter (mm) = 29, Body tube length (mm) = 400, Nose cone length (mm) = 80, Nose type (1-3) = 1 = 10 input(s) provided
Calculate Total Cd
Total Cd = CdNose + CdBody + CdBase + CdFins + CdInterference + CdProtuberance
0.8932 = 0.8932
Calculate Nose cone Cd
Nose cone Cd = CdNosePressure + CdNoseFriction
0.0493 = 0.0493
Calculate Body tube Cd
Body tube Cd = Cf * (bodyWettedArea / Aref)
0.2387 = 0.2387

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