Drag force calculator

This drag force calculator uses D = ½ · ρ · v² · Cd · A: a 1 m² flat plate at 50 km/h at sea level feels about 151 N. Air density follows from the altitude you enter.

Example: Body shape: Flat plate (Cd 1.28) · Reference area 1 m² · Speed 50 · Unit: km/h · Altitude above sea level 0 m → Result: Drag force 151.4 N, power 2.103 kW. Source: NASA Glenn Research Center, The Drag Equation: D = Cd · A · 0.5 · ρ · V² (read 13.10.2026). Updated: 13 October 2026.

Body shape

NASA wind-tunnel Cd values (frontal area as reference); use “Own Cd value” for other bodies.

Reference area

m²

The area facing the airflow (frontal area).

Speed

Unit

Altitude above sea level

0 to 11,000 m (troposphere).

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Result

Result: Drag force 151.4 N, power 2.103 kW
Details: Quantity Value
Drag force F 151.4 N
Power P = F · v 2,103 W
Cd value 1.28
Air density ρ 1.2266 kg/m³
Speed 13.89 m/s
Force at double the speed 605.7 N; Calculated with F = ½ · ρ · v² · Cd · A (NASA Glenn). Air density from the NASA troposphere model. Real Cd values depend on shape and flow; the presets are wind-tunnel values.

Quantity	Value
Drag force F	151.4 N
Power P = F · v	2,103 W
Cd value	1.28
Air density ρ	1.2266 kg/m³
Speed	13.89 m/s
Force at double the speed	605.7 N

How it is calculated

Drag D = ½ · ρ · v² · Cd · A. ρ is the air density, v the speed, Cd the drag coefficient and A the reference area (NASA Glenn, The Drag Equation). The power spent against drag is P = F · v.

Example

Flat plate, Cd = 1.28, A = 1 m², sea level (ρ = 1.2266 kg/m³): at 50 km/h (13.89 m/s) F = 0.5 · 1.2266 · 13.89² · 1.28 · 1 ≈ 151.4 N and P ≈ 2103 W.

Table: flat plate at different speeds

km/h	Force in N	Power in W
30	54.5	454
50	151.4	2103
100	605.7	16826
130	1023.7	36967

Force grows with the square of speed, power with the cube: doubling the speed means four times the force and eight times the power.

Cd values by shape (NASA)

Cd	Force at 100 km/h and 1 m² in N
1.28	605.7
1.14	539.5
0.295	139.6
0.045	21.3

Flat plate 1.28, wedge with its point downstream 1.14, bullet 0.295, airfoil 0.045 – measured in wind tunnels with the frontal area as reference. For a sphere NASA only gives a range of 0.07 to 0.5 because it depends on the Reynolds number.

Altitude and air density

Altitude in m	Air density in kg/m³
0	1.2266
1000	1.1133
2000	1.0081
3000	0.9107

Density and drag fall with altitude. For falling objects and friction see the free fall calculator and the friction calculator.

Frequently asked questions

How do you calculate drag force?

With D = ½ · ρ · v² · Cd · A. Example: Cd 1.28, 1 m², 50 km/h, ρ 1.2266 kg/m³ gives about 151 N.

What is the drag coefficient Cd?

A number that bundles the effects of shape and flow; NASA determines it in wind tunnels.

Why does power rise so steeply with speed?

Force grows with v² and power P = F · v with v³, so doubling the speed needs eight times the power.

Which area do I enter?

The frontal area seen from the flow direction; it must match the Cd value used.

Which air density is used?

The density from the NASA troposphere model for the altitude entered: 1.2266 kg/m³ at sea level.

Sources and legal basis

As of: 13 October 2026 · Editorial policy