Spin Rate Calculator

Step 1: Calculate RPM from Video

Use high-speed footage to count frames for one full rotation.

Step 2: Calculate Bauer Units

Measure spin efficiency relative to velocity.

What is Spin Rate?

Spin Rate is a measurement of how many times a ball rotates on its axis within one minute, expressed as Revolutions Per Minute (RPM). It is a critical metric in baseball pitching, as well as in golf and cricket, because the spin affects the trajectory of the ball through the Magnus effect.

A higher spin rate on a fastball generally creates more "lift" (or fights gravity longer), making the pitch appear to rise or stay up in the zone. Conversely, a lower spin rate with the right axis can produce sinking action.

How to Calculate Spin Rate from Video

If you do not have a Rapsodo or TrackMan radar, you can estimate spin rate using a high-speed camera (like an iPhone slo-mo mode usually recording at 120 or 240 FPS). The formula used by this calculator is:

RPM = (Camera FPS / Frames for 1 Rotation) × 60

• Camera FPS: The frame rate setting of your camera (e.g., 240 fps).
• Frames for 1 Rotation: Count exactly how many video frames it takes for the ball to complete one full 360-degree turn.

Understanding Bauer Units

The "Bauer Unit" is a normalization of spin rate relative to velocity. It helps determine if a pitcher has a high or low spin rate for their specific velocity.

Formula: Bauer Unit = RPM / Velocity (MPH)

Interpreting the Results

Bauer Unit	Classification	Ball Action (Fastball)
Below 23	Low Spin	Sinking action, induces ground balls.
23 – 25	League Average	Standard carry and drop.
Above 25	High Spin	"Rising" action, induces swings and misses.

Why Spin Rate Matters

In modern baseball analytics, spin rate is used to design pitches:

1. 4-Seam Fastballs: High spin rates are preferred to keep the ball up in the zone.
2. Curveballs/Sliders: High spin rates create sharper, tighter breaks.
3. Changeups: Lower spin rates are often preferred to kill lift and increase drop.

function calculateVideoRPM() { var fps = parseFloat(document.getElementById('cameraFps').value); var frames = parseFloat(document.getElementById('framesPerRotation').value); var resultBox = document.getElementById('videoResult'); if (isNaN(fps) || isNaN(frames) || frames <= 0 || fps <= 0) { alert("Please enter valid positive numbers for FPS and Frame count."); return; } // Calculation: (FPS / Frames per rotation) = Rotations per second. * 60 = RPM. var rpm = (fps / frames) * 60; var timePerRotation = (frames / fps) * 1000; // in milliseconds // Update UI document.getElementById('rpmOutput').innerHTML = Math.round(rpm) + " RPM"; document.getElementById('timeOutput').innerText = "One rotation takes: " + timePerRotation.toFixed(2) + " ms"; resultBox.style.display = "block"; // Optional: Auto-fill the second calculator for convenience document.getElementById('spinRateInput').value = Math.round(rpm); } function calculateBauer() { var vel = parseFloat(document.getElementById('pitchVelocity').value); var rpm = parseFloat(document.getElementById('spinRateInput').value); var resultBox = document.getElementById('bauerResult'); if (isNaN(vel) || isNaN(rpm) || vel <= 0 || rpm <= 0) { alert("Please enter valid positive numbers for Velocity and Spin Rate."); return; } // Calculation: RPM / Velocity var bu = rpm / vel; var interpretation = ""; if (bu = 23 && bu <= 25) { interpretation = "Average Spin (Standard)"; } else { interpretation = "High Spin (Rising Action)"; } document.getElementById('bauerOutput').innerText = bu.toFixed(2); document.getElementById('bauerInterp').innerText = interpretation; resultBox.style.display = "block"; }