Take-off distance estimate calculator
Take-off distance corrections multiply. Several small penalties together can easily double the book figure.
ft
%
kt
kt
%
Ground roll with safety factor
486m
- Unfactored ground roll
- 365
- Distance to clear 50 feet
- 826
- Ground roll in feet
- 1594
- Combined correction factor
- 1.044
- Density altitude factor
- 1.480
- Weight factor
- 0.903
- Wind factor
- 0.730
Show the working
- Book ground roll at sea level = 350
- Density altitude = 4000
- Weight as a share of maximum = 95
- Headwind = 8
- Rotation speed = 55
- Runway slope = 1
- Surface = 1
- Safety factor = 1.33
- Density altitude factor = 1 + 0.12 * 4000/1000 = 1.48
- Weight factor = (95/100)^2 = 0.9025
- Wind factor = 55 > 0 ? (1 - 8/55)^2 : 1 = 0.730 248
- slope_factor = 1 + 0.07 * 1 = 1.07
- Unfactored ground roll = 350 * 1.48 * 0.9025 * 0.730 248 * 1.07 * 1 = 365.284
- Ground roll with safety factor = 365.284 * 1.33 = 485.828
- Distance to clear 50 feet = 485.828 * 1.7 = 825.908
- Combined correction factor = 350 > 0 ? 365.284 / 350 : 0 = 1.043 67
- Ground roll in feet = 485.828 * 3.280839895013123 = 1593.92
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- roll = book roll x altitude x weight^2 x wind^2 x slope x surface
- take-off distance grows roughly with the square of weight and falls with the square of headwind fraction
These are rule-of-thumb multipliers. The aircraft flight manual chart is authoritative and accounts for the specific type.
A 1.33 safety factor on take-off is a common private-flying convention and is not a regulatory requirement everywhere.
This is a planning and study tool. Use certified charts, an approved flight manual and official publications for anything operational.