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Chapter 6 of 9

Estimating and Rate Analysis

In the AAI Manager (Civil) syllabus under Construction Technology, Equipment, Planning & Management · 2 parts

Principles & Types of Estimates · Analysis of Rates

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📑 Contents (15 sections)

Part 1 of 2

Principles & Types of Estimates

Last reviewed 16 Sept 2026 · 8 min read

What is an estimate?

An estimate is a calculation of the probable cost of a project before construction, prepared from drawings, specifications and current rates.

Purposes

Determine the approximate cost for deciding feasibility and obtaining administrative approval and financial sanction.
Arrange funds and budget allocations.
Invite tenders and compare bids (bill of quantities).
Plan quantities of materials, labour and equipment and schedule procurement.
Control expenditure during execution; prepare valuation of existing properties.

Data required

Drawings — plans, elevations, sections, detailed drawings.
Specifications — general and detailed (quality of materials and workmanship).
Rates — schedule of rates (e.g. CPWD/State PWD DSR) or analysed rates for items.
Site information — soil, access, leads for materials, local conditions.

Approximate (preliminary) estimates

Prepared quickly for feasibility and administrative approval, before detailed drawings exist.

Method	Basis	Formula / remarks
Plinth area method	Cost per unit plinth area of similar buildings in the locality	Cost = plinth area × plinth area rate; plinth area measured at floor level including external walls; separate rates for different floors/specifications
Cubic content (cubical) method	Cost per unit volume of similar buildings	Cost = volume × cubic rate; volume = plinth area × height (e.g. from floor/plinth level to top of roof) — better than plinth area for buildings of different heights
Service unit (unit base) method	Cost per unit of service provided	e.g. per bed (hospital), per student (school), per seat (theatre), per classroom, per km (road), per tonne of storage
Typical bay method	Cost of one typical bay (between column lines) in repetitive buildings	Cost = cost of one bay × number of bays (+ adjustments for end bays) — factories, warehouses, halls
Approximate quantity (bill) method	Approximate quantities of major items (e.g. per running metre of wall including foundation, superstructure, finishes) × rates	More accurate than area methods

Additions to building cost (commonly allowed as percentages of building cost when detailed estimates are not available): water supply and sanitary installations, electrical installations, and other services (often of the order of several per cent each), plus contingencies and supervision charges.

Detailed estimate (item rate estimate)

Prepared from complete drawings and specifications for technical sanction and tendering.

Steps

Details of measurements — each item of work is measured (number, length, breadth, height/depth) from drawings and quantities computed as per standard modes of measurement.
Abstract of estimated cost — quantities of each item multiplied by rates to get amounts; items grouped (earthwork, concrete, masonry, finishing etc.).
Additional provisions on the total:
- Contingencies — for unforeseen items and minor variations (commonly about 3–5%).
- Work-charged establishment — wages of staff employed specifically for the work (e.g. work supervisors, chowkidars) (commonly around 1.5–2%).
- Tools and plant, quality control, petty supervision, centage charges (departmental charges for design and supervision in deposit works) as per departmental rules.
Report explaining the need, design basis, specifications, rates adopted, cost and sources of funds.
Drawings and specifications attached.

Other types of estimates

Estimate	Purpose
Revised estimate	A detailed estimate prepared again when the sanctioned estimate is likely to be exceeded beyond permissible limits (as per departmental rules), or when there are material deviations from the original proposal — requires fresh sanction
Supplementary estimate	For additional works found necessary during execution that were not part of the original estimate
Annual repair (maintenance) estimate	For routine yearly maintenance — whitewashing, painting, minor repairs — often a small percentage of the capital cost
Special repair estimate	For major repairs beyond routine maintenance (e.g. re-roofing)
Complete estimate	Total cost of a project including land acquisition, buildings, services, roads, compound walls, establishment, etc.
Quantity estimate (quantity survey)	Only quantities of all items (used in tender documents as the bill of quantities)
Project estimate	Consolidated estimate for a large project with sub-works

Part 2 of 2

Analysis of Rates

Last reviewed 16 Sept 2026 · 7 min read

Rate analysis — meaning and purpose

Analysis of rates is the determination of the cost per unit of an item of work (per m³, m², kg etc.) from the quantities of materials and labour required, their current rates, and allowances for tools, plant, overheads and profit.

Purposes

Determine a reasonable rate for each item for estimates and tenders.
Fix rates for extra/substituted items not in the schedule.
Check the reasonableness of contractors' quoted rates.
Revise rates when material prices or wages change.
Prepare/update the schedule of rates.

Factors affecting rates

Specification and quality of materials and workmanship.
Location of the site — distance (lead) from sources of materials, transport facilities.
Quantity of work (economy of scale).
Labour rates and availability; local wages.
Site conditions — working space, water, weather, height, depth.
Profit, overheads and taxes.
Season and time allowed for completion.

Components of a rate

Rate = Materials + Labour + T&P + Water charges + Overheads and profit

Component	Typical treatment
Materials	Quantity per unit of work (including wastage) × rate at site (cost + carriage + loading/unloading + storage)
Labour	Number of mason/mazdoor/bhisti days per unit (from output or task work) × daily wage
Tools and plant (T&P), scaffolding	Lump sum or small percentage of labour cost, or actual hire charges of machinery
Water charges	Commonly about 1% of the cost of materials and labour (or as per departmental rules)
Contractor's profit and overheads	Commonly about 10% for profit plus overheads, often combined in schedules as around 15% of the cost (as per the department's analysis)

Percentages vary between departments and years; examinations commonly use water charges 1–1.5% and contractor's profit about 10%.

Schedule of rates and cost index

Schedule of rates (SOR) — list of item rates approved by a department for a region and period, e.g. CPWD Delhi Schedule of Rates (DSR) and state PWD SORs, prepared by analysis of rates.
Cost index — percentage used to update a base schedule (e.g. DSR) to the current cost level at a particular place and time; Estimated cost = base schedule amount × (1 + cost index %).
Market rate items — items not in the schedule, analysed from market rates of materials and labour.

Material requirements

Concrete — dry volume

When dry materials (cement, sand, coarse aggregate) are mixed with water and compacted, the wet volume is less than the sum of the loose dry volumes — voids are filled.

FormulaMaterials for concrete

Dry volume ≈ 1.52–1.57 × wet volume (commonly 1.54 for concrete)

For a nominal mix $1 : a : b$ by volume:

V_{ce m e n t} = \frac{1.54 V}{1 + a + b}, V_{s an d} = a V_{ce m e n t}, V_{a g g r e g a t e} = b V_{ce m e n t}

Cement in bags $= \frac{V _{ce m e n t} \times 1440}{50}$ (density of cement ≈ 1440 kg/m³; one bag = 50 kg ≈ 0.0347 m³)

Cement mortar

Dry volume ≈ 1.27–1.33 × wet volume (commonly taken as about 1.3, with some texts adding extra for wastage).

Brickwork

Nominal (with mortar) size of a modular brick: 200 × 100 × 100 mm → about 500 bricks per m³ of brickwork.
Actual modular brick 190 × 90 × 90 mm → volume of bricks in 1 m³ ≈ $500 \times 0.19 \times 0.09 \times 0.09 = 0.39$ m³ → wet mortar ≈ 0.25–0.30 m³ per m³ of brickwork (commonly taken as about 0.25–0.30 m³, with the frog and wastage allowance).
With traditional (non-modular) bricks, about 550 per m³ are commonly used in calculations; add wastage for bricks (often 5%).

Plastering

Wet mortar = area × thickness; add for filling joints, uneven surfaces and wastage (commonly 20–30%) before converting to dry volume.

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