Landing Distance Calculator
Correct your POH landing figures for density altitude, weight, wind, surface and slope, then check them against the runway available.
Enter the book figures from your POH (sea level, ISA, max landing weight, dry paved and level), then the conditions on the day. Elevation is always in feet, weights in any unit as long as both match.
- Landing distance required (from 50 ft)
- โ
- Ground roll
- โ
- Total correction
- โ
- Pressure altitude
- โ
- Density altitude
- โ
- Headwind / tailwind
- โ
- Crosswind
- โ
Where the correction comes from
A planning aid built on published rules of thumb, not a certified performance calculation. Always fly the numbers in your aircraft's current POH or AFM.
How it works
Start with the two numbers your flight manual gives for a sea-level, standard-day, maximum-weight
landing on a dry level runway: the ground roll and the total distance from 50 ft to a full stop.
Everything else is a correction on top. Pressure altitude comes from the field elevation and the
altimeter setting (PA = elevation + (29.92 โ inHg) ร 1000, or 27 ft per hPa below
1013.25). Density altitude follows from the temperature against the ISA value at that pressure
altitude, DA = PA + 118.8 ร (OAT โ ISA), where ISA cools by 1.98 ยฐC per 1,000 ft from
15 ยฐC at sea level. Thin air means a higher true airspeed at touchdown, and the energy the brakes
have to absorb grows with the square of that speed.
The corrections are the standard rules of thumb: 10% more distance per 1,000 ft of density
altitude, compounded; distance scaling with the square of the weight ratio; 10% less per 9 knots
of headwind and 10% more per 2 knots of tailwind; a surface factor of 1.15 for wet paved or short
dry grass, 1.35 for wet grass and 1.25 for soft ground or snow (UK CAA Safety Sense figures); and
5% for each 1% of downhill slope. Headwind and crosswind components come from the angle between
the wind and the runway, headwind = speed ร cos ฮธ and
crosswind = speed ร |sin ฮธ|, with any gust used for the crosswind and for a tailwind
so the answer stays on the cautious side. The 1.33 safety factor at the end is the margin the CAA
recommends private pilots apply, the same 33% public transport operations must add by rule.
Deliberately, no credit is taken for a density altitude below sea level or for an uphill slope, and runway designators and reported surface winds are both magnetic, so the two work together without a variation correction. Everything is arithmetic done in your browser: nothing about your aircraft, your weights or your destination is uploaded, and there is no sign-up and no tracking.
Frequently asked questions
How do I calculate landing distance required?
Take the landing ground roll and the distance from 50 ft from your flight manual at sea level, ISA and maximum landing weight, then correct each condition in turn. This tool derives pressure altitude and density altitude from elevation, altimeter setting and temperature, adds about 10% per 1,000 ft of density altitude, scales by the square of the weight ratio, applies the 10%-per-9-knots-headwind and 10%-per-2-knots-tailwind rules, multiplies by a surface factor for wet tarmac, grass or snow, adds 5% per 1% of downhill slope, and applies a 1.33 safety factor at the end.
Why is a tailwind so much worse than a headwind is good?
The rules of thumb are deliberately asymmetric: a headwind buys you 10% for every 9 knots, while a tailwind costs you 10% for every 2 knots. Landing distance grows with the square of the groundspeed at touchdown, so a small tailwind adds a surprising amount of energy that the brakes then have to absorb. A 5 knot tailwind on a short wet strip is often the difference between stopping and not.
What surface factors does the calculator use?
They follow the UK CAA Safety Sense figures for landing: wet paved multiplies the distance by 1.15, short dry grass by 1.15, wet grass by 1.35, and soft ground, snow or standing water by 1.25. Each 1% of downhill slope adds a further 5%. No credit is taken for an uphill slope or for a dry, grippy surface beyond the book figure.
What does the 1.33 safety factor mean?
It is the margin the UK CAA recommends private pilots add to the corrected landing distance, the same 33% that public transport operations must apply by rule. It covers the gap between a test pilot flying a new aeroplane to the book technique and a normal pilot on a normal day. If the runway available is less than the factored distance, the honest answer is to take fuel or bags out, wait for the wind to change, or go somewhere longer.