Physics

Prop Slip Calculator

Find propeller slip from theoretical and actual speed.

Theoretical speed

Actual speed

Calculated Output

Slip (%) 17.722

Formula: slip = (theoretical − actual) ÷ theoretical × 100

Step-by-Step Breakdown

1. Values used:

2. Theoretical speed = 79

3. Actual speed = 65

5. Slip = 17.722%

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The math behind it

slip = (theoretical − actual) ÷ theoretical × 100. Some slip is normal and necessary to generate thrust.

79 mph theoretical vs 65 actual → about 17.7% slip.

What's a good slip figure?

Around 10–15% for efficient props; very high slip suggests the wrong prop.