Free · Everyday planning calculators

Windsock Extension Heuristic

Convert a five-segment extension assumption to approximate knots and equivalent speed units.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

Three extended segments map to a heuristic nine knots, equivalent to 16.668 km/h.

Estimated knots = 3 × extended segments

Worked example

Enter these known values and leave the other values blank.

Number of segments (n)
3
Speed
9 kn
Speed [imperial]
10.4 mph
Speed [metric]
16.7 km/h

Assumptions and limitations

  • The three-knots-per-segment relation is an illustrative heuristic, not a calibrated intermediate wind-speed scale. FAA guidance specifies orientation by three knots and full extension at at least fifteen knots; a fully extended sock can mean stronger wind. Use measured wind for operational decisions.

Common questions

What does this estimate assume?

The three-knots-per-segment relation is an illustrative heuristic, not a calibrated intermediate wind-speed scale. FAA guidance specifies orientation by three knots and full extension at at least fifteen knots; a fully extended sock can mean stronger wind. Use measured wind for operational decisions.

Can I find a missing input?

Clear the unknown field and enter compatible known values. The controls retain supported inverse calculations, while rounded counts and one-way outputs stay directional.

References

Speed-unit conversion uses exactly 1852 meters per nautical mile and 1609.344 meters per international statute mile, replacing the rounded mph factor. The segment-to-knot relation remains an explicitly approximate visual heuristic.

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