Standard Cost Variance Analysis

Overview

Analyzes the differences between standard (planned) and actual costs, decomposing variances into price and quantity components. Identifies responsible departments and provides root cause hypotheses for manufacturing cost management.

When to Use This Skill

Use this skill in the following scenarios:

1. Monthly Cost Variance Reporting - Analyze standard vs. actual cost differences for manufacturing operations
   • 「今月の原価差異を分析して」「標準原価との乖離を計算して」
2. Cost Reduction Effectiveness Measurement - Evaluate whether cost reduction initiatives achieved target
   • 「原価低減活動の効果を測定して」「コスト削減の進捗を確認して」
3. Procurement Price Monitoring - Track material price variances against standards
   • 「材料の価格差異を確認して」「仕入価格の変動を分析して」
4. Production Efficiency Analysis - Identify quantity/efficiency variances in manufacturing
   • 「製造効率の差異を分析して」「数量差異の原因を特定して」
5. Responsibility Accounting - Assign variance responsibility to appropriate departments
   • 「差異の責任部門を特定して」「部門別の原価管理レポートを作って」

Prerequisites

Before running this skill, ensure the following data is available:

• Standard Cost Data: Standard price and standard quantity per item
• Actual Cost Data: Actual price and actual quantity per item
• Cost Category Classification: Each item classified as material, labor, or overhead
• Period Information: Target analysis period

Required CSV Format

item_name,cost_category,standard_price,actual_price,standard_quantity,actual_quantity
Eggs,material,2.50,3.20,100,105
Line Worker,labor,25.00,26.50,40,42
Equipment Depreciation,overhead,5000,5000,1,1

Required Columns:

Column	Type	Description
item_name	string	Cost item name
cost_category	string	material, labor, or overhead
standard_price	numeric	Standard (planned) unit price
actual_price	numeric	Actual unit price
standard_quantity	numeric	Standard quantity for actual output
actual_quantity	numeric	Actual quantity consumed

Cost Categories

• material: Raw materials and components (e.g., flour, eggs, packaging)
• labor: Direct labor (e.g., line workers, supervisors)
• overhead: Manufacturing overhead (e.g., depreciation, utilities, maintenance)

Workflow 1: Data Preparation

1. Validate Input Format: Verify CSV structure and required columns
2. Classify Cost Items: Confirm cost category assignments (material/labor/overhead)
3. Verify Standard Costs: Ensure standard costs reflect current approved standards
4. Handle Edge Cases: Address zero quantities, missing prices, and new items without standards

Workflow 2: Variance Decomposition

1. Calculate Price Variance per item:

   • Formula: (Actual Price - Standard Price) x Actual Quantity
   • Responsibility: Purchasing / Procurement department

2. Calculate Quantity Variance per item:

   • Formula: (Actual Quantity - Standard Quantity) x Standard Price
   • Responsibility: Production / Manufacturing department

3. Calculate Total Variance per item:

   • Formula: Price Variance + Quantity Variance
   • Verification: Must equal (Actual Price x Actual Quantity) - (Standard Price x Standard Quantity)

4. Determine Direction:

Total Variance	Direction	Meaning
Positive (+)	Unfavorable	Actual cost exceeds standard
Negative (-)	Favorable	Actual cost below standard
Zero	On Standard	Actual matches standard

5. Aggregate by Category: Compute subtotals for material, labor, and overhead

Workflow 3: Root Cause Analysis & Responsibility Mapping

1. Responsibility Assignment:

   • Price variances → Purchasing/Procurement
   • Quantity variances → Production/Manufacturing
   • Overhead volume variances → Management/Planning

2. Root Cause Hypotheses for each material variance:

   • Price (Unfavorable): Market price increase, supplier change, rush order premium, quality upgrade
   • Price (Favorable): Bulk discount, new supplier negotiation, lower-grade substitution
   • Quantity (Unfavorable): Waste/scrap increase, rework, equipment malfunction, skill gap
   • Quantity (Favorable): Process improvement, better equipment, skill enhancement

3. Cross-Category Analysis: Identify interactions (e.g., cheaper material causing more waste)

4. Trend Comparison: Compare to prior periods for systematic patterns

5. Action Recommendations: Prioritized corrective actions with responsible departments

Output

The analysis produces a structured cost variance report containing:

1. Executive Summary: Total variance by category, key highlights
2. Item-Level Detail: Price variance, quantity variance, and total per item with calculation basis
3. Category Subtotals: Aggregated variances by material/labor/overhead
4. Responsibility Matrix: Variance amounts mapped to responsible departments
5. Root Cause Analysis: Hypotheses and recommended actions for major variances

Output template: assets/cost_variance_report_template_ja.md (Japanese) or assets/cost_variance_report_template_en.md (English)

Resources

References (load into context for guidance)

• references/12_standard-cost_20260122.md - Standard cost (planned cost) concepts, bakery business case study with price/quantity variance decomposition
• references/11_ABC-store-profitability_20251213.md - Activity-Based Costing methodology for store-level cost allocation and profitability analysis

Assets (templates for output generation)

• assets/cost_variance_report_template_ja.md - Japanese cost variance analysis report template
• assets/cost_variance_report_template_en.md - English cost variance analysis report template

Best Practices

• Always decompose total variance into price and quantity components - the total alone is insufficient
• Verify that Price Variance + Quantity Variance = Total Variance as a calculation check
• Consider interdependencies between price and quantity (e.g., cheaper material may increase waste)
• Update standards periodically - outdated standards produce misleading variances
• Focus on controllable variances - market-driven price changes may not be actionable at the department level
• For overhead variances, consider separating into spending, efficiency, and volume components

Examples

Example: Bakery Manufacturing Cost Variance

Input Data:

item_name,cost_category,standard_price,actual_price,standard_quantity,actual_quantity
Flour (kg),material,200,220,500,520
Eggs (unit),material,30,28,1000,1050
Baker Hourly,labor,1500,1500,160,175
Oven Electricity,overhead,50,55,200,200

Analysis Output (Flour):

• Price Variance: (220 - 200) x 520 = +10,400 (Unfavorable) → Purchasing
• Quantity Variance: (520 - 500) x 200 = +4,000 (Unfavorable) → Production
• Total Variance: +14,400 (Unfavorable)
• Root Cause: Wheat price increase (price) + recipe adjustment for new product (quantity)

Category Summary:

Category	Price Variance	Quantity Variance	Total
Material	+8,300 (U)	+5,500 (U)	+13,800 (U)
Labor	0	+22,500 (U)	+22,500 (U)
Overhead	+1,000 (U)	0	+1,000 (U)
Total	+9,300 (U)	+28,000 (U)	+37,300 (U)