Runway Slope Takeoff Distance Calculator
Price an uphill takeoff in feet — the ~10%-per-1%-gradient planning rule, plus the uphill-takeoff vs downhill-tailwind comparison every one-way strip demands.
Gravity taxes the roll twice on a grade: a component of weight pulls backward and the climb-out starts lower relative to terrain. The 10%-per-1% figure is the standard planning rule; POH slope charts (where published) govern.
Formula
⚠️ Planning estimate only — your POH/AFM performance charts are the authoritative source. Always verify with official data, and apply your operator's safety factors. Not for airworthiness decisions.
Disclaimer: This tool is for general informational and estimation purposes only and is not professional financial, tax, accounting or legal advice. All figures are estimates — verify with a qualified professional before making decisions. Read the full disclaimer.
Price an uphill takeoff in feet — the ~10%-per-1%-gradient planning rule, plus the uphill-takeoff vs downhill-tailwind comparison every one-way strip demands.
About Runway Slope Takeoff Distance Calculator
Mountain strips force a question flatland training never asks: takeoff uphill into wind, or downhill with a tailwind? This calculator prices the gradient side of that trade — about 10% more ground roll per 1% of upslope — and converts the slope into its equivalent tailwind so both sides of the one-way-strip decision can be compared in the same currency. For gradients beyond about 2%, the answer is usually decided by the strip, not the windsock.
How to use Runway Slope Takeoff Distance Calculator
- 1Enter — sensible defaults are pre-filled so you see a worked result immediately.
- 2Read the live results: .
- 3Check the "With your numbers" line to see the formula distance × (1 + 0.10 × slope%); 1% up ≈ 2.2 kt of tailwind in cost substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Runway Slope Takeoff Distance Calculator?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula distance × (1 + 0.10 × slope%); 1% up ≈ 2.2 kt of tailwind in cost with sources cited on the page
- ✓Gravity taxes the roll twice on a grade: a component of weight pulls backward and the climb-out starts lower relative to terrain. The 10%-per-1% figure is the standard planning rule; POH slope charts (where published) govern.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
Where does 10% per 1% of slope come from?+
From resolving weight along the runway: a 1% grade adds a retarding force of about 1% of aircraft weight, which for typical light-aircraft thrust-to-weight ratios (0.25–0.3 at the start of the roll, falling through it) stretches the roll roughly 10%. UK CAA Safety Sense 7 publishes the same planning factor. Aircraft with anemic climb power suffer more.
Uphill into wind or downhill with tailwind — how do I decide?+
Convert both to distance and compare. This tool shows slope as equivalent tailwind (≈2.2 kt per 1%); our wind tool prices actual tailwind at 10% per 2 kt. Example: 2% upslope ≈ 4.4 kt tailwind equivalent — so taking off downhill into a 5 kt tailwind is roughly a wash on distance, and the obstacle picture then decides. Many strips publish the answer: 'land up, depart down, always.'
Does slope change the rotation or climb portion too?+
The headline correction covers the ground roll. But an upslope also tilts your liftoff trajectory relative to the obstacle plane — you break ground later and lower against terrain that is itself rising. On real one-way strips the published procedure (and a walk of the strip) trumps any single-factor calculation; treat this output as the entry ticket, not the full analysis.
How do I find a runway's actual gradient?+
The Chart Supplement / AIP entry lists it when it's significant (e.g. 'RWY 16: 1.9% up S'), and airport diagrams show threshold elevations you can difference and divide by length. For unpublished bush strips, walk it with a GPS or sight level — and remember gradients are often uneven: the average hides the steeper half that may sit exactly where you'll be slowest.
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