Industrial Minerals & Powder Processing calculator

Blend Uniformity Calculator

Estimate the coefficient of variation (CV%) for a blended mineral batch using the sample mean and standard deviation from grab samples. Use it to verify that your ribbon blender, tumble blender, or continuous mixer is producing a uniform product within specification.

What this calculator does

  • Estimate the coefficient of variation (CV%) for a blended mineral batch using sample mean and standard deviation to assess whether the blend meets uniformity specifications.
  • Use it when a quality manager or process engineer needs to verify that a ribbon blender, tumble blender, or continuous mixer is producing a uniform mineral blend within the customer specification (typically CV less than 5% to 10%).
  • Shows the coefficient of variation for a blended batch and whether it meets the uniformity specification.

Formula used

  • Blend CV% = (sample standard deviation / sample mean) x 100
  • Gap to limit = blend CV% - maximum acceptable CV%

Inputs explained

  • Sample mean (key component): Enter the average value of the tracked component from grab samples (e.g., CaCO3 percentage, SiO2 percentage, or GE brightness). Use at least 10 samples from different blend locations.
  • Sample standard deviation: Enter the standard deviation of the same grab sample results. Calculate from individual sample values using the standard formula.
  • Maximum acceptable CV%: Enter the maximum coefficient of variation allowed by the product spec or customer. Typical limits: 5% for critical blends, 10% for general industrial blends.

How to use the result

  • Use after blend validation sampling, during mixer qualification, for lot release decisions, or to compare blender types or mix times.
  • Results depend on sampling protocol (number of samples, sample size, sampling locations), analytical method accuracy, blend time, fill level, mixer type, particle size ratio, density ratio between components, and cohesive vs. free-flowing behavior. Validate with statistically valid sampling plans.

Common questions

  • What information do I need before using the Blend Uniformity calculator? You need the sample mean and standard deviation from at least 10 grab samples of the key tracked component, plus the maximum acceptable CV% from the product specification.
  • What does the result mean? The result shows the coefficient of variation (CV%) of your blend. Lower is better. A CV% below your spec limit means the blend is acceptably uniform.
  • When is the result only an estimate? Always. CV% accuracy depends on the number of samples, sample size, sampling locations, and analytical precision. Use a validated sampling plan for lot release decisions.
  • What decision can I make from the result? Use it to release or reject a batch, increase blend time, change mixer speed or fill level, justify a mixer upgrade, or demonstrate blend quality to customers.

Last reviewed 2026-05-12.