How do you calculate blend uniformity CV%?

Divide the sample standard deviation by the sample mean and multiply by 100. The order matters: standard deviation goes on top, mean on the bottom, entering them reversed inflates the result enormously.

What is a good blend CV% for a powder blend?

For pharmaceutical-grade blends, USP targets CV% at or below about 5-6%; many industrial mineral blends accept up to 7-10% depending on the spec. Lower is always tighter and more uniform.

Why did the calculator return a CV% in the hundreds or thousands?

That happens when the standard deviation and mean are entered in the wrong fields. CV% = (std dev / mean) × 100, so a large spread over a small mean produces an absurd value, always confirm the mean is the larger, central value.

What does the headroom to limit tell me?

It is your maximum acceptable CV% minus the computed CV%. A positive headroom means you are inside the limit and the blend passes; a negative headroom means it exceeds the limit and needs more mixing or investigation.

CV% vs standard deviation, which should I report?

Standard deviation is in the component's own units and only comparable within one concentration. CV% is dimensionless, so it lets you compare uniformity of a 32% major component against a 0.5% minor additive on the same scale.

How many samples do I need for a meaningful CV%?

Pull stratified samples from multiple locations and depths, typically at least 10, so the standard deviation reflects real spatial variation rather than sampling noise.

Industrial Minerals & Powder Processing calculator

Blend Uniformity Calculator

Blend uniformity expressed as coefficient of variation (CV%) measures how consistently a key component is distributed through a mineral or powder blend by comparing the spread of sample assays to their average. Quality engineers and blend operators at filler, pigment, ceramic, and dry-mix producers use it because a low CV% means every bag or batch carries the target composition, while a high CV% signals segregation or under-mixing. The calculator divides the sample standard deviation by the sample mean and reports the gap to your acceptance limit, so a single number tells you whether the blend passes. It is the standard, dimensionless way to compare uniformity across components measured at very different concentrations.

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%).
It computes CV% as sample standard deviation divided by sample mean times 100, then subtracts it from your maximum acceptable CV% to show the headroom to limit.

Formula used

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

Inputs explained

Sample standard deviation: Spread of the key-component assays across samples. Should be small relative to the mean.
Sample mean (key component): Average assay of the key component across all samples - the larger, central value.
Maximum acceptable CV%:

How to use the result

Use it after pulling stratified samples from a blend to verify mixing before release, or to compare uniformity between blend recipes or mixer settings.
CV% is only meaningful when the mean and standard deviation come from the same component and units; swapping the two inputs, or using too few samples, produces a misleading score.

Current U.S. benchmarks

Steel mill PPI stands at 374.203 (BLS, Jul 2026), up 22.5% from a year earlier. New factory orders are up 7.4% year over year (Census).

Common questions

How do you calculate blend uniformity CV%? Divide the sample standard deviation by the sample mean and multiply by 100. The order matters: standard deviation goes on top, mean on the bottom, entering them reversed inflates the result enormously.
What is a good blend CV% for a powder blend? For pharmaceutical-grade blends, USP targets CV% at or below about 5-6%; many industrial mineral blends accept up to 7-10% depending on the spec. Lower is always tighter and more uniform.
Why did the calculator return a CV% in the hundreds or thousands? That happens when the standard deviation and mean are entered in the wrong fields. CV% = (std dev / mean) × 100, so a large spread over a small mean produces an absurd value, always confirm the mean is the larger, central value.
What does the headroom to limit tell me? It is your maximum acceptable CV% minus the computed CV%. A positive headroom means you are inside the limit and the blend passes; a negative headroom means it exceeds the limit and needs more mixing or investigation.
CV% vs standard deviation, which should I report? Standard deviation is in the component's own units and only comparable within one concentration. CV% is dimensionless, so it lets you compare uniformity of a 32% major component against a 0.5% minor additive on the same scale.

Last reviewed 2026-08-11.