What is the drag force formula?

F_d = 0.5 × Cd × ρ × A × v², where Cd is the dimensionless drag coefficient, ρ (rho) is the fluid density in kg/m³, A is the reference area in m², and v is velocity in m/s. The result is in newtons.

What drag coefficient should I use?

Common values: smooth sphere ≈ 0.47, long cylinder ≈ 1.0, flat plate perpendicular to flow ≈ 1.28, streamlined teardrop ≈ 0.04, passenger car ≈ 0.25–0.35. The tool provides common presets.

What is standard air density?

At sea level and 15 °C (ISA standard), ρ = 1.225 kg/m³. Density decreases with altitude and increases with lower temperatures. At 2000 m altitude it is roughly 1.007 kg/m³.

What is the reference area?

For bluff bodies (cars, cyclists), use the frontal cross-sectional area — the silhouette area the object presents to the flow. For wings and flat plates, the planform (top-view) area is used depending on convention.

How does drag change with speed?

Drag scales with v², so doubling the speed quadruples the drag force. This is why aerodynamic efficiency matters far more at high speeds than at low speeds.

Drag Force Calculator

Enter drag coefficient, air density, reference area, and velocity to compute aerodynamic drag force in newtons.

Inputs

Shape preset

Drag coefficient C_d (dimensionless)

Fluid density ρ (kg/m³)

Standard sea-level air = 1.225 kg/m³. Water = 998 kg/m³.

Reference area A (m²)

Velocity v (m/s)

Results

Fill in the inputs and press Calculate.

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Summary

This drag force calculator applies the standard aerodynamic drag equation F = 0.5 × Cd × ρ × A × v² to compute the resistive force on an object moving through a fluid. Enter the drag coefficient, fluid density, reference area, and velocity to get the drag force in newtons and the dynamic pressure in pascals. Preset drag coefficients for common shapes are included as a starting point.

How it works

Select a preset shape (sphere, cylinder, flat plate, streamlined body) or enter a custom drag coefficient.
Enter the air (or fluid) density in kg/m³ — 1.225 kg/m³ is standard sea-level air.
Enter the reference (frontal) area in square metres.
Enter the object velocity in metres per second.
Read the drag force in newtons and the dynamic pressure in the results panel.

Use cases

Estimate aerodynamic drag on a vehicle at highway speed.
Size parachutes for load drops or recovery systems.
Compute drag on a sports ball (baseball, soccer ball, golf ball).
Check drag on a cyclist or runner for performance analysis.
Validate CFD results against hand calculations.
Teach the drag equation in physics or engineering courses.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu