Rate of Climb Calculator
Solve the excess-power climb equation for R/C, thrust, drag, velocity, or weight — with reference tables and a live R/C-vs-velocity chart.
Curve holds T, D and W at your current input values and varies V — showing why R/C changes with airspeed even before drag itself changes with speed.
| Aircraft type | Typical R/C |
|---|---|
| Light single-engine (e.g. C172) | ~3.5 m/s (700 ft/min) |
| Light twin | ~6–8 m/s (1,200–1,600 ft/min) |
| Business jet | ~15–20 m/s (3,000–4,000 ft/min) |
| Airliner (initial climb) | ~10–15 m/s (2,000–3,000 ft/min) |
| Aerobatic / high T/W aircraft | 25+ m/s (5,000+ ft/min) |
| Aircraft type | Typical T/W |
|---|---|
| Light single-engine, prop | 0.10 – 0.20 |
| Airliner, cruise climb | 0.25 – 0.35 |
| Business jet | 0.30 – 0.45 |
| Aerobatic aircraft | 0.50 – 0.90 |
| Fighter jet (military power) | 0.8 – 1.3+ |
Thrust ↑, Drag fixed
More excess thrust (T−D) directly increases climb rate — this is the whole point of climb power settings.
Drag ↑
More drag eats directly into excess thrust, reducing climb rate one-for-one in force terms.
Velocity ↑
Climb rate scales with V for a fixed excess-thrust force — this is why best rate-of-climb speed (V_y) is a specific, non-trivial airspeed.
Weight ↑
Heavier aircraft climb more slowly for the same excess power — R/C is inversely proportional to weight.
What Is Rate of Climb?
Rate of climb (R/C) is the vertical speed at which an aircraft gains altitude. It comes directly from the aircraft's excess power — the power left over once drag has been overcome — divided by the aircraft's weight. This is why R/C is sometimes called "specific excess power."
Rate of Climb Formula
Here, (T − D) is the net excess thrust force. Multiplying by velocity converts that force into excess power, and dividing by weight converts excess power into a climb speed.
How to Calculate Rate of Climb
Choose the unknown variable above, enter the other four in whichever units suit your data, and the calculator rearranges the formula automatically:
| Solve for | Rearranged formula |
|---|---|
| R/C | R/C = (T − D) × V / W |
| T | T = R/C × W / V + D |
| D | D = T − R/C × W / V |
| V | V = R/C × W / (T − D) |
| W | W = (T − D) × V / R/C |
Rate of Climb Formula Variables
| Symbol | Meaning | Typical unit |
|---|---|---|
| R/C | Rate of climb | m/s, ft/min |
| T | Thrust | N, kN, lbf |
| D | Drag | N, kN, lbf |
| V | True airspeed | m/s, km/h, kt |
| W | Aircraft weight | N, kN, lbf |
How Thrust and Drag Affect Climb Rate
Only the difference between thrust and drag matters — the excess thrust available to accelerate the aircraft upward rather than just maintain level flight. As thrust falls or drag rises (e.g. with altitude, weight, or configuration changes), excess thrust and climb rate both shrink.
How Velocity Affects Climb Rate
For a fixed excess thrust force, climb rate rises with airspeed — but in practice thrust and drag both change with speed too, which is why every aircraft has a specific best rate-of-climb speed (V_y) rather than "faster is always better."
How Weight Affects Climb Rate
Weight sits in the denominator, so climb rate falls as weight rises for the same excess power — a heavily loaded aircraft climbs noticeably more slowly than a lightly loaded one.
Rate of Climb Calculation Example
R/C = (9,000 − 6,000) × 60 / 45,000
R/C = 4.0 m/s (≈ 787 ft/min)
Frequently Asked Questions
Excess thrust is thrust minus drag — the portion of engine output not used to overcome drag. It's the only part of thrust available to climb, so R/C only ever depends on this difference, never on thrust or drag alone.
It gives R/C at whatever velocity you enter. Finding V_y requires evaluating R/C across a range of speeds (since T and D both vary with V) and picking the maximum — the chart above illustrates the shape of that trade-off.
Yes — if drag exceeds thrust, (T − D) is negative and the aircraft descends rather than climbs at that condition.
No — W here is a force (weight = mass × gravitational acceleration), matching the force units used for thrust and drag so the equation stays dimensionally consistent.
Variables
| Symbol | Quantity | Unit |
|---|---|---|
| R/C | Rate of climb | m/s |
| T | Thrust | N |
| D | Drag | N |
| V | True airspeed | m/s |
| W | Weight | N |
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| Parameter | Value |
|---|---|
| T | 20,000 N |
| D | 15,000 N |
| V | 120 m/s |
| W | 80,000 N |
| Parameter | Value |
|---|---|
| T | 30,000 N |
| D | 20,000 N |
| V | 150 m/s |
| W | 90,000 N |
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
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