Calculate drag-only thrust required, drag coefficient, air density, airspeed or reference area with metric and imperial units. Use the area convention associated with the drag coefficient.

Drag-only estimate: thrust equals drag for steady level motion with thrust aligned to the motion. Use speed relative to air and the reference area used for C_d.

Use frontal area only when the drag coefficient uses frontal area.

Related Calculators

Thrust Required Formula

The calculator uses the drag equation. For steady level motion with aligned thrust and no other unbalanced along-path forces, thrust required is equal to aerodynamic drag.

T = 0.5 × Cd × rho × V² × A

Rearranged forms:

Cd = (2 × T) / (rho × V² × A)
rho = (2 × T) / (Cd × V² × A)
V = sqrt((2 × T) / (Cd × rho × A))
A = (2 × T) / (Cd × rho × V²)
  • T = thrust required, in newtons or pounds-force
  • Cd = drag coefficient, unitless
  • rho = air density
  • V = speed relative to air
  • A = reference area used to define Cd (frontal area only when that convention applies)

This drag-only calculation does not include rolling resistance, climb force, acceleration or propulsion losses. Wind must be accounted for in speed relative to air; ground speed alone is insufficient.

Useful Tables

The numerical ranges below are illustrative assumptions, not verified typical ranges or recommended defaults. Air density depends on pressure and temperature; use measured or appropriate atmospheric data. Use a drag coefficient measured for the same reference area, orientation and flow regime.

Condition Illustrative density assumption Notes
Sea level, standard atmosphere 1.225 kg/m³ Standard sea-level reference; actual conditions vary
Warm low-altitude day 1.15 to 1.20 kg/m³ Lower density reduces drag
High altitude Below 1.0 kg/m³ Depends strongly on altitude and temperature
Object type Illustrative Cd assumption Comment
Streamlined car 0.20 to 0.35 Varies with shape and underbody design
SUV or truck 0.35 to 0.60 Larger frontal area also increases thrust required
Cyclist upright 0.7 to 1.1 Position changes the result a lot
Flat plate facing flow 1.1 to 1.3 High-drag reference shape

Result Notes

With density, area and drag coefficient held constant, doubling airspeed makes aerodynamic drag four times larger. The coefficient itself can change with flow conditions.

Use consistent, real-world inputs. A small error in frontal area or drag coefficient can noticeably change the final thrust value.