Aviation Calcs

Takeoff / landing distance

Takeoff and Landing Distance Correction Calculator

Start from a POH or AFM baseline distance and apply the handbook factors for wind, weight, density altitude, slope, and surface. A headwind of 10% of liftoff speed reduces ground roll by 19%; a 10% tailwind increases it by 21%, matching the Pilot’s Handbook of Aeronautical Knowledge. These are planning estimates — the airplane’s charts always win.

I want to correct

Distance is scaled by (W / Wref)², the PHAK square-of-weight rule for ground roll.

same units as the wind, typically kt
negative for a tailwind

The factor is ((V − Vw) / V)². Use the runway selection or crosswind calculator if you have a wind direction instead of a component.

ft
ft, often 0

The primary density factor is 1/σ (constant-thrust, first-order). The training rule of “+10% per 1,000 ft DA” is also shown; it is usually more conservative. Get DA from the density altitude calculator.

percent, positive uphill in the direction of the roll

Slope uses a 5% distance change per 1% slope (takeoff lengthens uphill; landing lengthens downhill). Grass factors are typical CAA / training planning figures, not a POH chart.

Corrected distance

—

Advertisement
Ad slot — 728×90 desktop / 320×100 mobile

Wind and weight (PHAK)

Takeoff and landing ground roll scale, to first order, with the square of the groundspeed at liftoff or touchdown. With a runway-component wind Vw (positive headwind):

fwind = ((V − Vw) / V)²

A headwind of 10% of V therefore cuts distance by 19% (0.9² = 0.81). A 10% tailwind increases it by 21% (1.1² = 1.21). Those are the figures in FAA-H-8083-25, Chapter 11. Weight enters the same way, because stall and liftoff speed grow with √W:

fweight = (W / Wref)²

Density altitude

Liftoff TAS for a given indicated speed grows as 1/√σ, so distance grows at least as 1/σ if thrust is constant. That is the primary density factor on this page, using the U.S. Standard Atmosphere 1976 density ratio at the density altitudes you enter. Propeller airplanes are often worse, because thrust also falls with density; treat 1/σ as a lower bound and prefer the POH chart. A common training rule of thumb — about +10% distance per 1,000 ft of density altitude — is shown alongside and is usually more conservative.

Slope and surface

A widely used planning factor (UK CAA Safety Sense and many training syllabi) is a 5% distance change per 1% of runway slope: takeoff lengthens on an upslope, landing lengthens on a downslope. Typical firm-dry-grass factors are about ×1.20 on takeoff and ×1.15 on landing; wet grass is about ×1.30 and ×1.35; wet pavement is often taken as ×1.15 on landing and unchanged on takeoff. Soft, snow, or otherwise contaminated surfaces do not have a single reliable multiplier, so this page will not invent one.

The factors multiply:

D = Dref × fweight × fwind × fdensity × fslope × fsurface

Sources

FAA-H-8083-25 Pilot’s Handbook of Aeronautical Knowledge, Chapter 11, Aircraft Performance (wind and weight); FAA Airplane Flying Handbook (takeoff, landing, density altitude); UK CAA Safety Sense / aeroplane performance planning factors (slope and grass); U.S. Standard Atmosphere 1976 for σ. For density altitude itself, use the density altitude calculator. For a wet-runway speed check, see hydroplaning speed.

Frequently asked questions

Why does a 10% headwind only save 19%, not 10%?

Ground roll scales with the square of groundspeed. Cutting the groundspeed at liftoff by 10% cuts distance by 1 − 0.9² = 19%. A 10% tailwind works the other way: 1.1² = 1.21, a 21% increase. Those are the PHAK memory items.

Should I use the 10% per 1,000 ft DA rule or 1/σ?

The 1/σ factor is the first-order constant-thrust physics and is usually milder (about +9% at 3,000 ft DA). The 10%-per-thousand-feet rule is a conservative training memory item. Neither replaces the POH chart, and a propeller airplane in thin air can be worse than 1/σ.

Can I use this instead of the POH takeoff chart?

No. Start from a POH baseline only when you already have one, and treat the result as a cross-check. Flap setting, runway slope as published, mixture, and technique all live in the airplane’s charts, not in a generic multiplier.