---
title: "Estimating and costing; principle of units"
subject: "Estimating and Costing"
chapter: 1
key: "semester_7/estimating_and_costing:estimating-costing-principle-units"
source: https://www.bctengineer.com/q/semester_7/estimating_and_costing/estimating-costing-principle-units
site: BCT Engineering
---

# Estimating and costing; principle of units

Estimating and Costing · Chapter 1: Introduction

- Asked in: 2080 Baisakh, 2+3 marks
- Video: [Fundamentals of Estimating and Costing | Unit of measurement | Desired Accuracy as per IS 1200](https://www.youtube.com/watch?v=61dvTS9VD-w) — Tech Civil
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/estimating_and_costing/estimating-costing-principle-units
- Whole chapter: https://www.bctengineer.com/md/semester_7/estimating_and_costing/chapter-1

## Question

What is estimating and costing? Explain the principle of units.

## Short answer

Estimating calculates quantities from drawings and specifications; costing multiplies them by rates and adds overhead, profit, contingency and taxes. Units are chosen by geometry: m for linear work, m² for area work, m³ for volume work, numbers, weight, and lump sum. Measurement is net work in place.

## Answer

#### Estimating and costing
**Estimating** is calculating the quantities of the items of work and the materials required, from drawings and specifications. **Costing** is finding the cost of these quantities by multiplying them with the proper rates (rate analysis), and adding overhead, profit, contingency and taxes. Together they give the probable cost of a project before construction.

#### Principle of units
Each item of work is measured in the unit that suits its geometry, and that same unit is used for payment:
- **Length (m):** cornice, skirting, railing, pipes, drains.
- **Area (m²):** plastering, flooring, painting, formwork, roofing sheets.
- **Volume (m³):** excavation, concrete, brick and stone masonry, filling.
- **Number (nos./set):** doors, windows, W.C., lighting points.
- **Weight (kg/tonne):** reinforcement, structural steel.
- **Lump sum:** items that cannot be measured.

The measurement is of the net work in place; the description of the item covers materials, labour and tools included in the rate.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is costing?
   A. Calculating quantities from drawings only
   B. Measuring completed work
   C. Finding the cost of the quantities by multiplying with rates and adding overhead, profit, contingency and taxes
   D. Preparing drawings
   Answer: C. Estimating gives quantities; costing applies rates. (Key point: Costing)

2. What is the principle of units?
   A. All items are measured in m³
   B. Payment unit differs from measurement unit
   C. Units are chosen by the contractor
   D. Each item is measured in the unit suiting its geometry and the same unit is used for payment
   Answer: D. The geometry decides the unit. (Key point: Principle of units)

3. Which item is measured by weight?
   A. Reinforcement
   B. Plastering
   C. Doors
   D. Skirting
   Answer: A. Reinforcement and structural steel are in kg or tonne. (Key point: Unit examples)

## Related in Estimating and Costing

- [Purposes of estimating and costing](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Apurposes-of-estimating) — Estimating and Costing, chapter 1, asked 4×
- [Principle of units; data for detailed estimate](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aprinciple-units-data-required) — Estimating and Costing, chapter 1
- [Units: excavation, well steining, conductor, cornice](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aunits-excavation-well-steining-conductor) — Estimating and Costing, chapter 1
- [Measurement and units: pointing, steel](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Ameasure-pointing-steel-units) — Estimating and Costing, chapter 1
- [Five units of length, area, volume](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Afive-units-length-area-volume) — Estimating and Costing, chapter 1
- [Units of measurement and payment, civil and sanitary](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aunits-civil-sanitary-works) — Estimating and Costing, chapter 1

## Related in other subjects

- [Standard costing variances, 3000 vs 2500 units](https://www.bctengineer.com/question.md?key=semester_6%2Fengineering_economics%3Avariances-3000-units-27-days) — Engineering Economics, chapter 1
- [Standard costing variances for a building company](https://www.bctengineer.com/question.md?key=semester_6%2Fengineering_economics%3Avariances-cement-mason-standard-costing) — Engineering Economics, chapter 1