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quantity-takeoff-calculator skill

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This skill helps estimate construction quantities by calculating concrete volumes, steel weights, earthwork, and material takeoffs from drawings or BIM.

npx playbooks add skill a5c-ai/babysitter --skill quantity-takeoff-calculator

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SKILL.md

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---
name: quantity-takeoff-calculator
description: Construction quantity takeoff skill for concrete, steel, earthwork, and materials
allowed-tools:
  - Read
  - Write
  - Glob
  - Grep
  - Edit
  - Bash
metadata:
  specialization: civil-engineering
  domain: science
  category: Construction Management
  skill-id: CIV-SK-026
---

# Quantity Takeoff Calculator Skill

## Purpose

The Quantity Takeoff Calculator Skill calculates construction quantities including concrete volumes, steel weights, earthwork quantities, and material takeoffs from drawings or BIM models.

## Capabilities

- Concrete volume calculation
- Steel weight calculation
- Earthwork quantities
- Pipe and conduit lengths
- Area calculations (formwork, finishes)
- Unit conversion
- Waste factor application
- BIM-based takeoff

## Usage Guidelines

### When to Use
- Estimating project quantities
- Supporting cost estimates
- Verifying contractor quantities
- Planning material procurement

### Prerequisites
- Design documents available
- Takeoff categories defined
- Unit system established
- Waste factors identified

### Best Practices
- Use consistent methods
- Document measurement rules
- Apply appropriate waste factors
- Cross-check critical items

## Process Integration

This skill integrates with:
- Construction Cost Estimation
- Specifications Development

## Configuration

```yaml
quantity-takeoff-calculator:
  categories:
    - concrete
    - steel
    - earthwork
    - masonry
    - piping
  sources:
    - bim-model
    - drawings
    - cad
  units:
    - imperial
    - metric
```

## Output Artifacts

- Quantity summaries
- Material takeoffs
- Cost backup data
- BOM reports

Overview

This skill performs construction quantity takeoffs for concrete, steel, earthwork, piping, and general material lists. It produces volume, area, length, and weight outputs and supports unit conversion and waste factor application. Outputs include summarized quantities, material takeoffs, and cost backup data useful for estimating and procurement. It can work from drawings, CAD, or BIM sources when available.

How this skill works

The calculator inspects defined takeoff categories and parses source inputs (BIM models, drawings, or CAD files) to extract geometry and measurements. It computes concrete volumes, steel weights, earthwork cut/fill, pipe lengths, and area-based items, applying unit conversions and user-defined waste factors. Results are grouped into category summaries, BOM-style reports, and exportable cost backup files. Configuration options let you set units, measurement rules, and which sources to trust for each item.

When to use it

Preparing initial quantity estimates for bid or tender submissions
Validating contractor takeoffs and change orders
Sizing procurement and materials delivery schedules
Cross-checking quantities from BIM versus 2D drawings
Generating base data for cost estimation and BOM creation

Best practices

Define takeoff categories and measurement rules before running calculations
Use consistent unit settings (imperial or metric) across the project
Set and document waste factors per material and trade
Cross-check critical items manually or with a second tool for high-risk quantities
Prefer BIM geometry for dimensional accuracy when available

Example use cases

Calculate slab, beam, and column concrete volumes for a building shell estimate
Generate steel tonnage from structural models to produce supplier RFQs
Compute cut and fill volumes for site grading and earthwork planning
Produce piping lengths and fittings counts for MEP procurement
Export quantity summaries to support a cost estimator's rate build-up

FAQ

What input sources does the calculator accept?

It accepts BIM models, CAD/drawing inputs, and manual measurement entries; results converge via configured measurement rules.

How are waste factors applied?

Waste factors are configurable per category or item and are applied after base quantity calculation to produce ordered material quantities.