---
title: "Approximate estimate: what and when"
subject: "Estimating and Costing"
chapter: 3
key: "semester_7/estimating_and_costing:approximate-estimate-when-needed"
source: https://www.bctengineer.com/q/semester_7/estimating_and_costing/approximate-estimate-when-needed
site: BCT Engineering
---

# Approximate estimate: what and when

Estimating and Costing · Chapter 3: Types of Estimate

- Asked in: 2076 Chaitra, 4 marks; 2070 Chaitra, 4+4 marks; 2080 Baisakh, 2 marks; 2081 Baisakh, 2 marks; 2068 Baisakh (old course), 4 marks; 2066 Bhadra (old course), 2 marks (asked 6 times)
- Video: [Introduction to Approximate Estimate - Estimates - Quantity Survey Estimation and Valuation](https://www.youtube.com/watch?v=ReRCjh8PcjE) — 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/approximate-estimate-when-needed
- Whole chapter: https://www.bctengineer.com/md/semester_7/estimating_and_costing/chapter-3

## Question

What do you understand by approximate (preliminary) estimate? When and why is it prepared? Also write a short note on it.

## Short answer

An approximate or preliminary estimate is a rough cost prepared before detailed design for feasibility, administrative approval, comparing alternatives and funding. It uses plinth area or unit rates and is usually within 10 to 15% of final cost.

## Answer

#### Meaning
An approximate (preliminary) estimate is a rough estimate of the probable cost of a project, prepared quickly from the general requirements and past experience, without detailed drawings or item quantities.

#### When and why it is prepared
1. At the **planning stage**, to decide whether the project is feasible and affordable.
2. To obtain **administrative approval** and budget allocation from the ministry/municipality.
3. To **compare alternatives** (sites, designs, types of structure).
4. For **funding** and loan applications, and in the preparation of the annual programme.
5. When there is no time or data for detailed estimation, as at the start of a design.

#### Short note
- **Methods:** plinth area method, cubic content (cube) rate method, unit base (per bed, per student, per km, per cum of storage) method, approximate quantity method, and the cost of a similar building in the locality.
- **Data:** area of the building, the prevailing plinth area rate, percentages for services and contingency.
- **Contents:** cost of the civil works (plinth area x rate), special architectural treatment, water supply and sanitary, electrical works, external services, contingency and supervision charge.
- **Accuracy:** about 10 to 15% from the final cost; it is not used for tendering.
- It is followed by the **detailed estimate** after design is completed.

## Check yourself

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

1. What is an approximate (preliminary) estimate?
   A. An item-wise estimate from final drawings
   B. A rough probable cost prepared quickly from general requirements and experience, without detailed drawings
   C. The final bill after completion
   D. A tender priced by the contractor
   Answer: B. It is prepared before detailed design. (Key point: Meaning)

2. Which is a reason for preparing a preliminary estimate?
   A. To pay the contractor
   B. To prepare working drawings
   C. To get administrative approval and compare alternatives
   D. To measure completed work
   Answer: C. It supports feasibility, approval, funding and comparison of options. (Key point: Why prepared)

3. What accuracy is expected from a preliminary estimate?
   A. Exact to 1%
   B. Within 50%
   C. Accurate enough for tender documents
   D. About 10 to 15% from the final cost; not used for tendering
   Answer: D. It is rough and followed by a detailed estimate. (Key point: Accuracy)

4. What follows a preliminary estimate after design is completed?
   A. The detailed estimate
   B. A supplementary estimate
   C. A complete estimate only
   D. Nothing; it is final
   Answer: A. Detailed estimate is based on drawings and item quantities. (Key point: Follow-up)

## Related in Estimating and Costing

- [Methods of approximate estimate](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Amethods-approx-estimate-suitability) — Estimating and Costing, chapter 3
- [Procedure of preliminary estimate (office building)](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aprelim-estimate-procedure-office) — Estimating and Costing, chapter 3, asked 2×
- [Preliminary estimate: 4-storied office, 2000 m²](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aprelim-est-office-2000-d) — Estimating and Costing, chapter 3, asked 2×
- [Preliminary estimate: office, 3275 m² carpet](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aprelim-est-office-3275) — Estimating and Costing, chapter 3
- [Preliminary estimate: residential, 500 m² carpet](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aprelim-est-residential-500) — Estimating and Costing, chapter 3
- [Preliminary estimate: school for 600 students](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aprelim-est-school-600) — Estimating and Costing, chapter 3