# Cwicr Waste Calculator > Calculate material waste factors and losses using CWICR norms. Apply waste percentages, cutting losses, and spillage factors to material quantities. - Skill: `tools-only/cwicr-waste-calculator` (Agent Skill, multi-file: 3 files) - Install (CLI): `npx skillmds add tools-only/cwicr-waste-calculator` - Raw SKILL.md: https://api.skillmd.com/api/skills/tools-only/cwicr-waste-calculator/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tools-only (https://skillmd.com/u/tools-only) - Updated: 2026-09-08 - Page: https://skillmd.com/skills/tools-only/cwicr-waste-calculator --- # CWICR Waste Calculator ## Business Case ### Problem Statement Material estimates need waste factors: - Cutting/trimming losses - Spillage and breakage - Overordering requirements - Different waste by material type ### Solution Systematic waste calculation using CWICR material data with industry-standard waste factors by material category. ### Business Value - **Accurate ordering** - Include realistic waste - **Cost control** - Budget for actual usage - **Sustainability** - Track and reduce waste - **Benchmarking** - Compare waste across projects ## Technical Implementation ```python import pandas as pd import numpy as np from typing import Dict, Any, List, Optional from dataclasses import dataclass from enum import Enum class WasteCategory(Enum): """Waste category types.""" CUTTING = "cutting" # Cutting/trimming losses SPILLAGE = "spillage" # Liquid material spillage BREAKAGE = "breakage" # Damaged materials OVERRUN = "overrun" # Installation overrun THEFT = "theft" # Site theft allowance WEATHER = "weather" # Weather damage @dataclass class WasteFactor: """Waste factor for a material.""" material_code: str material_name: str base_quantity: float unit: str cutting_waste_pct: float spillage_pct: float breakage_pct: float overrun_pct: float total_waste_pct: float quantity_with_waste: float waste_quantity: float waste_cost: float # Industry standard waste factors by material type WASTE_FACTORS = { 'concrete': { 'cutting': 0.02, 'spillage': 0.03, 'breakage': 0.0, 'overrun': 0.02 }, 'rebar': { 'cutting': 0.05, 'spillage': 0.0, 'breakage': 0.01, 'overrun': 0.02 }, 'brick': { 'cutting': 0.05, 'spillage': 0.0, 'breakage': 0.03, 'overrun': 0.02 }, 'block': { 'cutting': 0.04, 'spillage': 0.0, 'breakage': 0.02, 'overrun': 0.02 }, 'lumber': { 'cutting': 0.10, 'spillage': 0.0, 'breakage': 0.02, 'overrun': 0.03 }, 'plywood': { 'cutting': 0.12, 'spillage': 0.0, 'breakage': 0.02, 'overrun': 0.02 }, 'drywall': { 'cutting': 0.10, 'spillage': 0.0, 'breakage': 0.03, 'overrun': 0.02 }, 'tile': { 'cutting': 0.10, 'spillage': 0.0, 'breakage': 0.05, 'overrun': 0.03 }, 'paint': { 'cutting': 0.0, 'spillage': 0.05, 'breakage': 0.0, 'overrun': 0.10 }, 'mortar': { 'cutting': 0.0, 'spillage': 0.05, 'breakage': 0.0, 'overrun': 0.03 }, 'insulation': { 'cutting': 0.08, 'spillage': 0.0, 'breakage': 0.02, 'overrun': 0.03 }, 'roofing': { 'cutting': 0.10, 'spillage': 0.0, 'breakage': 0.02, 'overrun': 0.05 }, 'pipe': { 'cutting': 0.05, 'spillage': 0.0, 'breakage': 0.01, 'overrun': 0.02 }, 'wire': { 'cutting': 0.03, 'spillage': 0.0, 'breakage': 0.0, 'overrun': 0.05 }, 'conduit': { 'cutting': 0.05, 'spillage': 0.0, 'breakage': 0.01, 'overrun': 0.02 }, 'duct': { 'cutting': 0.08, 'spillage': 0.0, 'breakage': 0.01, 'overrun': 0.03 }, 'steel': { 'cutting': 0.03, 'spillage': 0.0, 'breakage': 0.0, 'overrun': 0.02 }, 'glass': { 'cutting': 0.05, 'spillage': 0.0, 'breakage': 0.05, 'overrun': 0.02 }, 'flooring': { 'cutting': 0.10, 'spillage': 0.0, 'breakage': 0.02, 'overrun': 0.03 }, 'adhesive': { 'cutting': 0.0, 'spillage': 0.08, 'breakage': 0.0, 'overrun': 0.05 }, 'default': { 'cutting': 0.05, 'spillage': 0.02, 'breakage': 0.02, 'overrun': 0.03 } } class CWICRWasteCalculator: """Calculate material waste using CWICR data.""" def __init__(self, cwicr_data: pd.DataFrame): self.materials = cwicr_data self._index_data() def _index_data(self): """Index materials data.""" if 'material_code' in self.materials.columns: self._mat_index = self.materials.set_index('material_code') elif 'work_item_code' in self.materials.columns: self._mat_index = self.materials.set_index('work_item_code') else: self._mat_index = None def _detect_material_type(self, description: str) -> str: """Detect material type from description.""" desc_lower = str(description).lower() for mat_type in WASTE_FACTORS.keys(): if mat_type in desc_lower: return mat_type # Check common synonyms synonyms = { 'concrete': ['beton', 'cement'], 'rebar': ['reinforcement', 'armature', 'арматура'], 'brick': ['кирпич', 'block'], 'lumber': ['wood', 'timber', 'древесина'], 'drywall': ['gypsum', 'plasterboard', 'гипсокартон'], 'tile': ['ceramic', 'плитка', 'керамика'], 'paint': ['краска', 'coating'], 'insulation': ['изоляция', 'утеплитель'], 'pipe': ['труба', 'piping'], 'wire': ['провод', 'cable', 'кабель'] } for mat_type, words in synonyms.items(): if any(word in desc_lower for word in words): return mat_type return 'default' def get_waste_factors(self, material_type: str) -> Dict[str, float]: """Get waste factors for material type.""" return WASTE_FACTORS.get(material_type, WASTE_FACTORS['default']) def calculate_waste(self, material_code: str, base_quantity: float, unit_cost: float = 0, custom_factors: Dict[str, float] = None) -> WasteFactor: """Calculate waste for a material.""" # Get material info material_name = material_code unit = "unit" if self._mat_index is not None and material_code in self._mat_index.index: mat = self._mat_index.loc[material_code] material_name = str(mat.get('description', mat.get('material_description', material_code))) unit = str(mat.get('unit', mat.get('material_unit', 'unit'))) if unit_cost == 0: unit_cost = float(mat.get('material_cost', mat.get('unit_cost', 0)) or 0) # Detect material type and get factors mat_type = self._detect_material_type(material_name) factors = custom_factors or self.get_waste_factors(mat_type) cutting = factors.get('cutting', 0) spillage = factors.get('spillage', 0) breakage = factors.get('breakage', 0) overrun = factors.get('overrun', 0) # Calculate total waste total_waste_pct = cutting + spillage + breakage + overrun waste_quantity = base_quantity * total_waste_pct quantity_with_waste = base_quantity + waste_quantity waste_cost = waste_quantity * unit_cost return WasteFactor( material_code=material_code, material_name=material_name, base_quantity=base_quantity, unit=unit, cutting_waste_pct=round(cutting * 100, 1), spillage_pct=round(spillage * 100, 1), breakage_pct=round(breakage * 100, 1), overrun_pct=round(overrun * 100, 1), total_waste_pct=round(total_waste_pct * 100, 1), quantity_with_waste=round(quantity_with_waste, 2), waste_quantity=round(waste_quantity, 2), waste_cost=round(waste_cost, 2) ) def calculate_project_waste(self, materials: List[Dict[str, Any]]) -> Dict[str, Any]: """Calculate waste for entire project.""" results = [] total_base_cost = 0 total_waste_cost = 0 for mat in materials: code = mat.get('material_code', mat.get('code')) qty = mat.get('quantity', 0) cost = mat.get('unit_cost', 0) custom = mat.get('waste_factors') waste = self.calculate_waste(code, qty, cost, custom) results.append(waste) total_base_cost += qty * cost total_waste_cost += waste.waste_cost # Summary by waste category by_category = { 'cutting': sum(r.cutting_waste_pct * r.base_quantity / 100 for r in results), 'spillage': sum(r.spillage_pct * r.base_quantity / 100 for r in results), 'breakage': sum(r.breakage_pct * r.base_quantity / 100 for r in results), 'overrun': sum(r.overrun_pct * r.base_quantity / 100 for r in results) } return { 'materials': results, 'total_base_cost': round(total_base_cost, 2), 'total_waste_cost': round(total_waste_cost, 2), 'waste_percentage': round(total_waste_cost / total_base_cost * 100, 1) if total_base_cost > 0 else 0, 'by_category': by_category, 'order_quantity_increase': round(sum(r.waste_quantity for r in results), 2) } def optimize_cutting(self, material_code: str, required_lengths: List[float], stock_length: float) -> Dict[str, Any]: """Optimize cutting to minimize waste (1D cutting stock problem).""" # Simple first-fit decreasing algorithm sorted_lengths = sorted(required_lengths, reverse=True) stock_pieces = [] waste_per_piece = [] for length in sorted_lengths: placed = False for i, remaining in enumerate(stock_pieces): if remaining >= length: stock_pieces[i] -= length placed = True break if not placed: stock_pieces.append(stock_length - length) total_stock_needed = len(stock_pieces) total_material = total_stock_needed * stock_length total_used = sum(required_lengths) total_waste = total_material - total_used waste_pct = total_waste / total_material * 100 if total_material > 0 else 0 return { 'material_code': material_code, 'stock_pieces_needed': total_stock_needed, 'stock_length': stock_length, 'total_material': round(total_material, 2), 'total_used': round(total_used, 2), 'total_waste': round(total_waste, 2), 'waste_percentage': round(waste_pct, 1), 'cutting_efficiency': round(100 - waste_pct, 1) } def export_waste_report(self, project_waste: Dict[str, Any], output_path: str) -> str: """Export waste report to Excel.""" with pd.ExcelWriter(output_path, engine='openpyxl') as writer: # Summary summary_df = pd.DataFrame([{ 'Total Base Cost': project_waste['total_base_cost'], 'Total Waste Cost': project_waste['total_waste_cost'], 'Waste Percentage': project_waste['waste_percentage'], 'Order Increase': project_waste['order_quantity_increase'] }]) summary_df.to_excel(writer, sheet_name='Summary', index=False) # Materials mat_df = pd.DataFrame([ { 'Material': m.material_name, 'Base Qty': m.base_quantity, 'Unit': m.unit, 'Cutting %': m.cutting_waste_pct, 'Spillage %': m.spillage_pct, 'Breakage %': m.breakage_pct, 'Overrun %': m.overrun_pct, 'Total Waste %': m.total_waste_pct, 'Order Qty': m.quantity_with_waste, 'Waste Cost': m.waste_cost } for m in project_waste['materials'] ]) mat_df.to_excel(writer, sheet_name='Materials', index=False) return output_path ``` ## Quick Start ```python # Load CWICR data cwicr = pd.read_parquet("ddc_cwicr_en.parquet") # Initialize calculator waste_calc = CWICRWasteCalculator(cwicr) # Calculate waste for single material waste = waste_calc.calculate_waste( material_code="CONC-001", base_quantity=100, unit_cost=150 ) print(f"Base Qty: {waste.base_quantity}") print(f"Order Qty: {waste.quantity_with_waste}") print(f"Waste: {waste.total_waste_pct}%") print(f"Waste Cost: ${waste.waste_cost:,.2f}") ``` ## Common Use Cases ### 1. Project-Wide Waste ```python materials = [ {'code': 'CONC-001', 'quantity': 200, 'unit_cost': 150}, {'code': 'REBAR-002', 'quantity': 5000, 'unit_cost': 1.2}, {'code': 'BRICK-003', 'quantity': 10000, 'unit_cost': 0.50} ] project = waste_calc.calculate_project_waste(materials) print(f"Total Waste Cost: ${project['total_waste_cost']:,.2f}") ``` ### 2. Cutting Optimization ```python cutting = waste_calc.optimize_cutting( material_code="REBAR-001", required_lengths=[2.5, 3.0, 1.8, 2.2, 4.0, 3.5], stock_length=6.0 ) print(f"Efficiency: {cutting['cutting_efficiency']}%") ``` ### 3. Custom Waste Factors ```python custom_factors = {'cutting': 0.15, 'spillage': 0, 'breakage': 0.05, 'overrun': 0.05} waste = waste_calc.calculate_waste("TILE-001", 500, 25, custom_factors) ``` ## Resources - **GitHub**: [OpenConstructionEstimate-DDC-CWICR](https://github.com/datadrivenconstruction/OpenConstructionEstimate-DDC-CWICR) - **DDC Book**: Chapter 3.1 - Material Waste Management