Spindle Speed Calculator

Optimal whorl size from target twist and drafting speed.

Spindle weight (oz)

Whorl diameter (in)

Drop length (in)

Target TPI

Tab to move between fields

Initial RPM

184

Average RPM120

Spin time (sec)5.8

Revolutions per drop12

TPI per drop0.39

Drops per yard19

Moment of inertia (kg·m²)0

Needed Revs180

How to Use This Calculator

Weigh your spindle and enter the total weight in ounces (whorl + shaft).
Measure the whorl diameter in inches and enter it.
Enter the drop length in inches from your hand to the lowest point of the suspended spindle.
Enter your target TPI (twist per inch) for the yarn you are spinning.
Read the initial RPM, average RPM, and spin time in seconds to understand your spindle's performance.
Use the drops per yard output to plan your drafting pace — more drops per yard means more spin sessions per yard of yarn.

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