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Formula & Calculator

Rate of Climb

Vertical speed achievable from the excess of thrust over drag at a given airspeed and weight.

Written by the Vorzep Team

Aircraft PerformancePropulsionClimb

Rate of Climb Calculator

R/C = (T − D) · V / W
Select the variable to solve for, then enter the other four values
R/CTDVW
Solve for:
Aircraft Presets
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Unit System
System:
Enter the other four values
m/s
N
N
m/s
kg
R/C = rate of climb (m/s or ft/s) T > D for positive climb Excess thrust = T − D W = weight (N or lbf)

Variables

SymbolQuantityUnit
R/CRate of climbm/s
TThrustN
DDragN
VTrue airspeedm/s
WWeightN

What it means

Rate of climb (ROC) is the vertical component of the aircraft’s velocity, representing the ability to gain altitude. The formula shows that ROC is proportional to the excess power (T−D)V divided by weight. This is derived from the energy balance: power available minus power required gives the excess power that can be used for climbing. ROC is a key performance metric for takeoff, obstacle clearance, and climb segments. It is used to determine the aircraft’s ceiling (absolute and service), and to plan climb profiles. In design, maximising ROC requires a powerful engine and a clean aerodynamic configuration. Understanding ROC is essential for flight planning and for comparing aircraft performance.

Worked example

Rate of Climb – Two Examples

Real‑World
Scenario: An aircraft has T = 20,000 N, D = 15,000 N, V = 120 m/s, W = 80,000 N. Find rate of climb.
ParameterValue
T20,000 N
D15,000 N
V120 m/s
W80,000 N
1R/C = (T-D)·V/W = (5000×120)/80000 = 600000/80000 = 7.5 m/s
Result 7.5 m/s ✓ Good
Scenario: T = 30,000 N, D = 20,000 N, V = 150 m/s, W = 90,000 N. Find R/C.
ParameterValue
T30,000 N
D20,000 N
V150 m/s
W90,000 N
1R/C = (10000×150)/90000 = 1,500,000/90000 = 16.67 m/s
Result 16.7 m/s ✓ Powerful
Key insight: Rate of climb = excess power / weight – power available minus power required.

Common mistakes

  • Rate of climb R/C: R/C = (T − D)·V / W – in m/s.
  • Thrust T and drag D: In Newtons.
  • Velocity V: True airspeed.
  • Weight W: In Newtons.
  • Excess power: (T−D)·V is the excess power available for climb.

Applications

Rate of climb, R/C = (T − D)·V/W, gives the vertical speed of an aircraft during climb. It is a primary performance metric, determining how quickly an aircraft can gain altitude. Engineers use this formula to evaluate climb performance for different phases (takeoff, en‑route climb), to size engines for required climb gradients, and to assess airfield obstacle clearance. It is also used in the definition of service and absolute ceilings. By optimising the thrust‑to‑weight ratio and aerodynamic efficiency, engineers can improve climb rate. Understanding R/C is essential for flight planning and for meeting regulatory climb gradient requirements for safe operations.

  • Takeoff and initial climb performance analysis
  • Engine sizing and thrust‑to‑weight optimisation
  • Obstacle clearance and departure path design
  • Service ceiling and absolute ceiling determination
  • Fuel‑time calculations for climb segments