How to Calculate Non-Conformance Rate (Calculator & Guide)
Non-Conformance Rate (NCR) is a critical quality performance indicator (KPI) used in manufacturing, construction, and service industries. It measures the percentage of products or services that fail to meet specified quality standards. Understanding and reducing your NCR is essential for minimizing waste, reducing costs, and maintaining customer satisfaction.
Use the calculator below to quickly determine your Non-Conformance Rate based on your inspection data.
Non-Conformance Rate Calculator
The total size of the batch or lot checked.
The number of items rejected or requiring rework.
Non-Conformance Rate (NCR):0%
Conformity Rate (Yield):0%
Parts Per Million (PPM) Defective:0
function calculateNCR() {
// Get input values
var totalUnitsStr = document.getElementById('totalUnits').value;
var defectiveUnitsStr = document.getElementById('defectiveUnits').value;
var errorDiv = document.getElementById('errorMsg');
var resultsDiv = document.getElementById('resultsBox');
// Reset display
errorDiv.style.display = 'none';
resultsDiv.style.display = 'none';
// Parse values
var total = parseFloat(totalUnitsStr);
var defects = parseFloat(defectiveUnitsStr);
// Validation logic
if (isNaN(total) || isNaN(defects)) {
errorDiv.innerText = "Please enter valid numbers for both fields.";
errorDiv.style.display = 'block';
return;
}
if (total <= 0) {
errorDiv.innerText = "Total units must be greater than zero.";
errorDiv.style.display = 'block';
return;
}
if (defects total) {
errorDiv.innerText = "Number of non-conforming units cannot exceed total units.";
errorDiv.style.display = 'block';
return;
}
// Calculation Logic
var ncr = (defects / total) * 100;
var yieldRate = 100 – ncr;
var ppm = (defects / total) * 1000000;
// Update DOM elements
document.getElementById('ncrResult').innerText = ncr.toFixed(2) + "%";
document.getElementById('yieldResult').innerText = yieldRate.toFixed(2) + "%";
document.getElementById('ppmResult').innerText = Math.round(ppm).toLocaleString();
// Show results
resultsDiv.style.display = 'block';
}
What is Non-Conformance Rate?
The Non-Conformance Rate (often abbreviated as NCR or called Defect Rate) quantifies the proportion of output that fails to meet quality acceptance criteria. It is a fundamental metric in Quality Management Systems (QMS) such as ISO 9001.
A "non-conformance" can range from a minor cosmetic scratch to a major functional failure. Tracking this rate allows businesses to identify systemic issues in production lines, supplier quality, or internal processes.
The Non-Conformance Rate Formula
Formula:
NCR = (Number of Non-Conforming Units / Total Units Checked) × 100
Where:
Number of Non-Conforming Units: Items that are scrapped, rejected, or require rework.
Total Units Checked: The total volume of production or the sample size of the inspection batch.
Calculation Example
Imagine a factory produces 5,000 widgets in a single shift. During quality control inspection, 125 widgets are found to be defective.
To calculate the rate:
Divide 125 by 5,000 = 0.025
Multiply by 100 = 2.5%
The Non-Conformance Rate for this shift is 2.5%.
Why is NCR Important?
Monitoring this metric provides several actionable insights:
Impact Area
Description
Cost of Poor Quality (COPQ)
High NCR directly increases costs related to scrap, rework, and warranty claims.
Process Stability
Fluctuations in NCR indicate unstable manufacturing processes or degrading equipment.
Supplier Performance
NCR can be applied to incoming raw materials to grade supplier quality.
How to Lower Your Non-Conformance Rate
Once you have calculated your rate using the tool above, the next step is reduction. Here are standard industry approaches:
Root Cause Analysis (RCA): Use tools like the "5 Whys" or Fishbone Diagrams to find out why defects are occurring, not just where.
Standard Operating Procedures (SOPs): Ensure that work instructions are clear, up-to-date, and accessible to all operators.
Preventive Maintenance: Regularly service machinery to prevent calibration drift that leads to defects.
Training: Invest in regular training for staff to ensure they understand quality standards and how to spot deviations early.
Frequently Asked Questions
What is an acceptable Non-Conformance Rate?
This varies wildly by industry. In aerospace or medical device manufacturing, the target is often near-zero (measured in Six Sigma or defects per million). In low-cost consumer goods, a rate of 1-2% might be acceptable. You must benchmark against your specific industry standards.
What is the difference between NCR and Yield?
They are inverses of each other. If your Non-Conformance Rate is 5%, your Yield (Conformity Rate) is 95%. Yield represents the percentage of "good" products.
Should I include reworked parts in the calculation?
Yes. Even if a part is fixed and eventually sold, it was originally non-conforming. To get an accurate picture of your "First Pass Yield" (quality efficiency), you must count the initial defect.