---
title: "Methods of approximate estimate"
subject: "Estimating and Costing"
chapter: 3
key: "semester_7/estimating_and_costing:methods-approx-estimate-suitability"
source: https://www.bctengineer.com/q/semester_7/estimating_and_costing/methods-approx-estimate-suitability
site: BCT Engineering
---

# Methods of approximate estimate

Estimating and Costing · Chapter 3: Types of Estimate

- Asked in: 2073 Shrawan, 6 marks
- Video: [Methods of Approximate Estimate - Estimates - Quantity Survey Estimation and Valuation](https://www.youtube.com/watch?v=MKscrK-y6Jc) — Ekeeda
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/estimating_and_costing/methods-approx-estimate-suitability
- Whole chapter: https://www.bctengineer.com/md/semester_7/estimating_and_costing/chapter-3

## Question

What are the different methods of preparing an approximate estimate? Write the suitability of each method.

## Short answer

Methods are: plinth area (similar buildings), cubic content (multi-storey), unit base (per bed/student/km), approximate quantity (plans available), typical bay (repeated units), cost of similar structure, and cost per km (roads, pipelines). Accuracy ranges 10–15%; approximate quantity is most accurate.

## Answer

| Method | How the cost is found | Suitability |
|---|---|---|
| 1. Plinth area method | Plinth area x plinth area rate of a similar building, plus extras for services | Buildings of similar type and finish; the commonest method for the preliminary estimate of offices, schools, hospitals |
| 2. Cubic content (cube rate) method | Volume of the building (plinth area x height) x rate per m³ | Multi-storey buildings, where height differs; more accurate than plinth area |
| 3. Unit base method | Cost per unit of function, such as per bed (hospital), per student (school), per seat (hall), per km (road) x number of units | Quick estimate of buildings and projects when the function is known |
| 4. Approximate quantity method | Total length of walls x rate per running metre of wall (covering the foundation and superstructure), plus roof and floor by area | Fairly accurate; used when the plan is ready but detailed drawings are not |
| 5. Typical bay method | Cost of one typical bay found in detail, multiplied by the number of bays, plus the remaining parts | Buildings with repeated bays or units, such as sheds, factories and hostels |
| 6. Cost of similar structure | The actual cost of a similar completed work, adjusted for time and place | Simple, when records of near-identical works are available |
| 7. Cost per kilometre/length | Rate per km of road, canal or pipeline | Linear projects (roads, canals, pipelines) |

The accuracy is about 10 to 15%; it is best for the approximate quantity method and least for the unit base method. The estimate must be adjusted for the location, the year and the specification.

## Check yourself

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

1. Which method is better for multi-storey buildings with differing heights?
   A. Cubic content (cube rate) method
   B. Cost per kilometre
   C. Plinth area method only
   D. Unit base method
   Answer: A. It uses volume x rate and is more accurate than plinth area. (Key point: Cube rate)

2. What does the unit base method use?
   A. Volume x rate
   B. Cost per unit of function (per bed, student, seat) x number of units
   C. Plinth area x rate
   D. Cost per km
   Answer: B. It is a quick estimate when the function is known. (Key point: Unit base)

3. Which method suits roads, canals and pipelines?
   A. Cube rate method
   B. Typical bay method
   C. Cost per kilometre/length
   D. Plinth area method
   Answer: C. Linear works are priced per length. (Key point: Linear projects)

4. The approximate quantity (typical bay) method suits:
   A. Single unique monuments
   B. Roads
   C. Dams only
   D. Buildings with repeated bays or units, such as sheds and hostels
   Answer: D. Quantities of one bay are multiplied. (Key point: Typical bay)

## Related in Estimating and Costing

- [Approximate estimate: what and when](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aapproximate-estimate-when-needed) — Estimating and Costing, chapter 3, asked 6×
- [Tasks in preparing building project estimate](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aworks-considered-building-project-estimate) — Estimating and Costing, chapter 5, asked 2×
- [Preparing a detailed estimate of a building](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aprepare-detailed-estimate-building) — Estimating and Costing, chapter 2, 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
- [Requisites of project estimate; factors](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Arequisites-project-estimate-factors) — Estimating and Costing, chapter 5