Calculator inputs
Enter baseline distance, then add site corrections.
Formula used
The calculator applies correction multipliers to a certified baseline takeoff distance for preliminary planning.
| Component | Factor | Rule |
|---|---|---|
| Elevation | Felev = 1 + 0.07·(Elev/300 m) | About 7% increase per 300 m elevation. |
| Temperature | Ftemp = 1 + 0.01·max(0, ΔT) | ΔT = OAT − ISA, ISA = 15 − 0.0065·Elev(m). |
| Gradient | Fgrad = 1 + 0.10·G (uphill) | Uphill slopes increase length; downhill reduces modestly. |
| Wind | Fwind = 1 − 0.01·HW, or 1 + 0.02·TW | Headwind helps slightly; tailwind increases requirement. |
| Surface / Condition / Obstacle | Fx = lookup multiplier | Simple multipliers for resistance and conservatism. |
| Safety margin | Fm = 1 + Margin/100 | Buffer applied after all corrections. |
Required runway length: Lreq = L0 · Π(Factors)
How to use this calculator
- Enter the baseline takeoff distance from approved performance data.
- Set elevation and the hottest expected outside air temperature.
- Provide runway gradient in the takeoff direction (uphill positive).
- Add wind component and choose headwind or tailwind.
- Select surface, condition, and obstacle allowance as needed.
- Choose a safety margin appropriate to project risk.
- Calculate, then export CSV or PDF for reporting.
Example data table
Use these cases to test inputs and outputs.
| Case | Base | Elev | OAT | Grad | Wind | Surface | Cond | Obs | Margin | Result (approx.) |
|---|---|---|---|---|---|---|---|---|---|---|
| A | 1800 m | 500 m | 30°C | 0.8% | 8 kt HW | Paved | Dry | Standard | 10% | ~2400–2600 m |
| B | 6000 ft | 3500 ft | 35°C | 1.5% | 5 kt TW | Gravel | Damp | Strict | 15% | ~9000–11000 ft |
| C | 1200 m | 0 m | 15°C | 0.0% | 0 kt | Grooved | Dry | None | 5% | ~1180–1300 m |