Net Weight Variance Calculator

Check average fill weight variance and coefficient of variation for process consistency review.

Target net weight (g)Sample average (g)Sample std dev (g)

Result

Average variance: -1.30 g

Coefficient of variation: 1.61%

How to Use This Tool

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Step 1: Set Target Weight

Enter the target net weight (declared weight) as shown on the product label or specification.

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Step 2: Input Sample Data

Provide the sample average weight and standard deviation from your production samples.

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Step 3: Review Variance Results

See the average variance and coefficient of variation to assess process consistency.

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Step 4: Process Adjustment

Use the results to adjust filling equipment and maintain regulatory compliance.

Example Results

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Canned Vegetables

Target: 400g, Sample: 398g, Std Dev: 4.5g

Result

Variance: -2g, CV: 1.13%

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Snack Bag Filling

Target: 100g, Sample: 102.5g, Std Dev: 2.8g

Result

Variance: +2.5g, CV: 2.73%

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Bottled Sauce

Target: 500g, Sample: 499.2g, Std Dev: 3.1g

Result

Variance: -0.8g, CV: 0.62%

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Frozen Meals

Target: 350g, Sample: 347g, Std Dev: 5.2g

Result

Variance: -3g, CV: 1.50%

Frequently Asked Questions

What is coefficient of variation (CV)?

CV is the ratio of standard deviation to the mean, expressed as a percentage. Lower CV indicates more consistent filling. A CV under 3% is typically considered good for most filling operations.

How do I calculate sample standard deviation?

Measure multiple filled packages (10-30 samples), calculate the average, then find the standard deviation using statistical software or the formula: sqrt(sum((x - mean)²) / (n-1)).

What is acceptable variance from target weight?

Regulatory requirements vary by region. In many jurisdictions, the average of samples must be at least the declared weight. Check local regulations like the FDA's Net Quantity of Contents rules.

How often should I check net weight variance?

For quality control, check at regular intervals during production runs, such as at the start, middle, and end of each shift, or according to your HACCP plan.

What if my variance is consistently negative?

Consistent negative variance (underfilling) may indicate equipment calibration issues or product density changes. Adjust filling equipment and verify settings to ensure compliance.