Calculator Inputs
Tip: terminal velocity requires a positive mass, and Reynolds number needs both characteristic length and viscosity.
Formula Used
Drag Force = 0.5 × ρ × Cd × A × v²
Dynamic Pressure = 0.5 × ρ × v²
Power = Drag Force × v
Drag Deceleration = Drag Force ÷ Mass
Terminal Velocity = √((2 × m × g) ÷ (ρ × Cd × A))
Reynolds Number = (ρ × v × L) ÷ μ
Here, ρ is density, Cd is drag coefficient, A is frontal area, v is relative velocity, m is mass, g is gravity, L is characteristic length, and μ is dynamic viscosity.
How to Use This Calculator
- Choose a shape preset or keep custom values.
- Enter object speed, wind speed, and wind direction.
- Provide drag coefficient, frontal area, and fluid density.
- Add mass for deceleration and terminal velocity calculations.
- Include characteristic length and viscosity for Reynolds number.
- Press the calculate button to view the result block above the form.
- Use CSV or PDF export buttons to save the result set.
Example Data Table
| Scenario | Speed (m/s) | Cd | Area (m²) | Density (kg/m³) | Approx. Drag (N) |
|---|---|---|---|---|---|
| Cyclist | 10 | 0.88 | 0.50 | 1.225 | 26.95 |
| Sedan Car | 27 | 0.30 | 2.20 | 1.225 | 294.70 |
| Baseball | 40 | 0.35 | 0.0042 | 1.225 | 1.44 |
| Parachute | 8 | 1.75 | 25.00 | 1.225 | 1715.00 |
Frequently Asked Questions
1) What does this calculator estimate?
It estimates drag force from fluid density, shape, frontal area, and relative speed. It also reports pressure, power loss, deceleration, terminal velocity, and Reynolds number when enough inputs are supplied.
2) Why does speed affect drag so strongly?
Drag depends on velocity squared. Doubling relative speed can roughly quadruple drag force when density, area, and drag coefficient stay constant.
3) What is relative velocity here?
Relative velocity is the speed difference between the object and surrounding air. Headwinds increase it, tailwinds reduce it, and crosswinds combine by vector effect.
4) What does drag coefficient mean?
Drag coefficient summarizes how streamlined or blunt a shape behaves in flow. Lower values usually mean smoother airflow and less drag at the same speed and area.
5) When is terminal velocity shown?
Terminal velocity appears when mass, gravity, density, drag coefficient, and frontal area are all positive. It represents the steady falling speed where drag balances weight.
6) Why include Reynolds number?
Reynolds number helps describe flow regime. It compares inertial and viscous effects using density, speed, characteristic length, and viscosity.
7) Can I use this for cars, balls, bikes, or parachutes?
Yes. Pick a preset or enter custom coefficients and areas. The formulas are general and work for many practical air-drag cases.
8) How accurate are the results?
Accuracy depends on input quality and assumptions. Real drag can vary with turbulence, changing body position, compressibility, and Reynolds number effects not fully captured here.