How to Calculate Relative Weight in House of Quality

Professional QFD Calculator & Strategic Guide

House of Quality (QFD) Weight Calculator

Enter Customer Importance and Relationship Strengths to determine the Relative Weight of Technical Requirements.

Customer Requirements (Voice of Customer)	Importance (1-10)	Tech Req 1 (e.g., Speed)	Tech Req 2 (e.g., Durability)	Tech Req 3 (e.g., Cost)
Requirement 1		None (0) Weak (1) Medium (3) Strong (9)	None (0) Weak (1) Medium (3) Strong (9)	None (0) Weak (1) Medium (3) Strong (9)
Requirement 2		None (0) Weak (1) Medium (3) Strong (9)	None (0) Weak (1) Medium (3) Strong (9)	None (0) Weak (1) Medium (3) Strong (9)
Requirement 3		None (0) Weak (1) Medium (3) Strong (9)	None (0) Weak (1) Medium (3) Strong (9)	None (0) Weak (1) Medium (3) Strong (9)
Requirement 4		None (0) Weak (1) Medium (3) Strong (9)	None (0) Weak (1) Medium (3) Strong (9)	None (0) Weak (1) Medium (3) Strong (9)
Requirement 5		None (0) Weak (1) Medium (3) Strong (9)	None (0) Weak (1) Medium (3) Strong (9)	None (0) Weak (1) Medium (3) Strong (9)

What is How to Calculate Relative Weight in House of Quality?

Understanding how to calculate relative weight in House of Quality is a fundamental skill in Quality Function Deployment (QFD). The House of Quality (HoQ) is a matrix-based tool used by engineers, product managers, and Six Sigma practitioners to translate customer requirements (often called the "Voice of the Customer") into specific technical specifications ("Voice of the Engineer").

The "Relative Weight" represents the percentage of importance assigned to a specific technical requirement relative to all others. It tells the development team where to focus their limited resources. If a technical feature has a high relative weight, it means it strongly influences the most important customer needs.

This calculation is critical because not all technical features are created equal. Some have a massive impact on customer satisfaction, while others are negligible. By calculating relative weights, teams avoid wasting time on low-impact features and ensure the final product aligns perfectly with market demands.

How to Calculate Relative Weight in House of Quality: The Formula

The mathematical process for how to calculate relative weight in House of Quality involves two main steps: calculating the Absolute Weight and then converting it to a Relative Weight percentage.

Step 1: Calculate Absolute Weight

For each Technical Requirement (column), the Absolute Weight is the sum of the products of the Customer Importance rating and the Relationship Strength.

Formula:
Absolute Weight (W_j) = Σ (Importance_i × Relationship_ij)

Step 2: Calculate Relative Weight

The Relative Weight is the Absolute Weight of a specific column divided by the sum of all Absolute Weights, multiplied by 100.

Formula:
Relative Weight (%) = (W_j / Σ W_all) × 100

Variable Definitions

Variable	Meaning	Typical Range
Importance (I)	How much the customer cares about a specific need.	1 to 5 or 1 to 10
Relationship (R)	Strength of the link between the customer need and technical requirement.	0, 1, 3, 9 (Standard QFD scale)
Absolute Weight (W)	Raw score indicating total impact.	0 to 500+
Relative Weight (%)	Normalized percentage of importance.	0% to 100%

Practical Examples of Calculation

Example 1: Designing a Premium Coffee Maker

Imagine a team designing a coffee maker. They have two customer needs: "Hot Coffee" (Importance: 9) and "Fast Brewing" (Importance: 6).

They have two technical requirements: "Heater Wattage" and "Pump Pressure".

• Heater Wattage: Strongly affects "Hot Coffee" (9) and moderately affects "Fast Brewing" (3).
• Pump Pressure: Weakly affects "Hot Coffee" (1) and strongly affects "Fast Brewing" (9).

Calculation for Heater Wattage:
(9 × 9) + (6 × 3) = 81 + 18 = 99 (Absolute Weight)

Calculation for Pump Pressure:
(9 × 1) + (6 × 9) = 9 + 54 = 63 (Absolute Weight)

Total Weight: 99 + 63 = 162

Relative Weight (Heater): (99 / 162) × 100 = 61.1%
Relative Weight (Pump): (63 / 162) × 100 = 38.9%

Conclusion: The engineering team should prioritize the Heater Wattage design.

How to Use This Calculator

Our tool simplifies the complex matrix arithmetic. Follow these steps:

1. Enter Importance Ratings: In the "Importance" column, rate how critical each customer requirement is (1-10).
2. Define Relationships: For each intersection of a Customer Requirement (row) and Technical Requirement (column), select the relationship strength:
   • Strong (9): Direct and powerful correlation.
   • Medium (3): Moderate correlation.
   • Weak (1): Slight correlation.
   • None (0): No correlation.
3. Analyze Results: The calculator instantly updates the Absolute and Relative Weights.
4. Review the Chart: The bar chart visualizes which technical requirement dominates the priority list.

Key Factors That Affect Relative Weight Results

When learning how to calculate relative weight in House of Quality, consider these influencing factors:

• Customer Importance Accuracy: If the initial customer ratings are biased or incorrect, the entire weight calculation will be skewed, leading to poor product decisions.
• Relationship Scale Choice: Using a 1-3-5 scale versus the standard 1-3-9 scale changes the separation between priorities. The 1-3-9 scale is preferred because it emphasizes strong relationships more heavily.
• Number of Requirements: Adding too many technical requirements can dilute the relative weights, making it harder to identify a clear "winner."
• Correlation Between Technical Requirements: (The "Roof" of the House). While not part of the basic weight calculation, conflicting technical requirements (e.g., "Lightweight" vs. "Durable") can complicate the implementation of high-weight features.
• Competitive Assessment: Sometimes weights are adjusted based on competitor performance, though this basic calculation focuses purely on internal prioritization.
• Zero-Sum Constraints: Remember that Relative Weight is a percentage. If one requirement goes up, others must mathematically go down, emphasizing the need for trade-offs.

Frequently Asked Questions (FAQ)

Why do we use 1, 3, 9 for relationship strengths?

This non-linear scale helps to clearly differentiate between strong and weak relationships. A "Strong" relationship (9) is three times more impactful than "Medium" (3), ensuring that critical technical features stand out in the final analysis.

Can relative weights be negative?

No. Since importance ratings and relationship strengths are positive integers (or zero), the resulting weights and percentages must always be positive.

What if the Total Absolute Weight is zero?

This implies that none of your technical requirements address any of the customer needs. This is a major design flaw, and you must revisit your technical specifications.

How many customer requirements should I include?

While our calculator shows 5, a real-world House of Quality might have 20-30. However, it is best to group them into hierarchies to keep the matrix manageable.

Does this calculator include the "Roof" of the House of Quality?

No, the "Roof" represents the correlation between technical requirements themselves (e.g., trade-offs). This calculator focuses specifically on the relationship matrix between Customer Needs and Technical Requirements.

Is Relative Weight the only metric for prioritization?

It is a primary metric, but teams should also consider cost, technical difficulty, and regulatory requirements before making final decisions.

What is the difference between Absolute and Relative Weight?

Absolute Weight is a raw score (e.g., 150 points), which is hard to interpret in isolation. Relative Weight is a percentage (e.g., 30%), which clearly shows the share of total importance.

Can I use this for software development?

Yes! In software, Customer Requirements are "User Stories" and Technical Requirements are "Features" or "Modules." The logic remains exactly the same.

maxDataVal) maxDataVal = data[i].rel; } var yMax = maxDataVal > 0 ? Math.ceil(maxDataVal / 10) * 10 : 100; // Round up to nearest 10 // Draw Axes ctx.beginPath(); ctx.moveTo(padding, padding); ctx.lineTo(padding, height – padding); ctx.lineTo(width – padding, height – padding); ctx.strokeStyle = '#ccc'; ctx.stroke(); // Draw Bars for (var i = 0; i < data.length; i++) { var val = data[i].rel; var barHeight = (val / yMax) * chartHeight; var x = padding + (i * spacing) + (spacing/2) – (barWidth/2); var y = height – padding – barHeight; // Bar ctx.fillStyle = '#004a99'; ctx.fillRect(x, y, barWidth, barHeight); // Label (Name) ctx.fillStyle = '#333'; ctx.font = '12px Arial'; ctx.textAlign = 'center'; ctx.fillText(data[i].name, x + barWidth/2, height – padding + 15); // Label (Value) ctx.fillStyle = '#000'; ctx.font = 'bold 12px Arial'; ctx.fillText(val.toFixed(1) + "%", x + barWidth/2, y – 5); } } function resetCalculator() { // Reset Inputs to defaults document.getElementById('imp1').value = 9; document.getElementById('imp2').value = 7; document.getElementById('imp3').value = 5; document.getElementById('imp4').value = 8; document.getElementById('imp5').value = 3; // Reset Selects (Just a few examples, resetting all to specific defaults) // Row 1 document.getElementById('r1_1').value = 9; document.getElementById('r1_2').value = 1; document.getElementById('r1_3').value = 3; // Row 2 document.getElementById('r2_1').value = 3; document.getElementById('r2_2').value = 9; document.getElementById('r2_3').value = 0; // Row 3 document.getElementById('r3_1').value = 0; document.getElementById('r3_2').value = 1; document.getElementById('r3_3').value = 9; // Row 4 document.getElementById('r4_1').value = 9; document.getElementById('r4_2').value = 0; document.getElementById('r4_3').value = 1; // Row 5 document.getElementById('r5_1').value = 1; document.getElementById('r5_2').value = 3; document.getElementById('r5_3').value = 9; calculateQFD(); } function copyResults() { var topName = document.getElementById('topTechReq').innerText; var topDetails = document.getElementById('topTechDetails').innerText; var text = "House of Quality Calculation Results:\n"; text += "Top Priority: " + topName + "\n"; text += topDetails + "\n\n"; // Get summary rows var rows = document.getElementById('summaryBody').getElementsByTagName('tr'); for(var i=0; i<rows.length; i++) { var cells = rows[i].getElementsByTagName('td'); text += cells[0].innerText + ": " + cells[2].innerText + " (Abs: " + cells[1].innerText + ")\n"; } var tempInput = document.createElement("textarea"); tempInput.value = text; document.body.appendChild(tempInput); tempInput.select(); document.execCommand("copy"); document.body.removeChild(tempInput); var btn = document.querySelector('.btn-copy'); var originalText = btn.innerText; btn.innerText = "Copied!"; setTimeout(function(){ btn.innerText = originalText; }, 2000); }