Estimating is measuring how much work a project needs from its drawings: excavation, concrete, steel, masonry and finishes. Costing multiplies each quantity by a unit rate and adds allowances such as contingency to give the budget.
A good estimate is traceable: another engineer can follow your drawings, dimensions, deductions and rates and reach the same total. Below are the types of estimate, the two wall-measurement methods, IS 1200 units and rate analysis, then a single room priced from excavation to the abstract of cost.
Detailed guides for each estimating task#
Each step of an estimate has its own guide:
| Your next task | Detailed guide |
|---|---|
| Budget a house and practise a wall estimate | Building estimate: house quantities, rates and Excel |
| Choose units and apply deductions | IS 1200 measurement rules by trade |
| Build a rate from materials and labour | Rate analysis in construction, with Excel examples |
| Turn a drawing set into measurement sheets and a bill | How to prepare a BOQ from drawings |
| Find scheduled items and understand their scope | CPWD DSR and state schedule of rates guide |
Types of estimate and when to use each#
There are five main types: preliminary, detailed, revised, supplementary and annual repair. Plinth area and cubical content are two ways of making the preliminary estimate.
| Type | Basis | When it is used |
|---|---|---|
| Preliminary or approximate | Comparable projects, area, volume or cost per functional unit | Early feasibility and an initial funding discussion before complete drawings exist |
| Plinth area | Built-up floor area × a comparable rate per m² or sq ft | Early building budgets where use, finishes, location and floor count are broadly known |
| Cubical content | Building volume × a comparable rate per m³ | Early comparison where building heights differ materially; use the same volume convention as the reference rate |
| Detailed | Item measurements from drawings and specifications × item rates | Tendering, contractor comparison and a working construction budget |
| Revised | Updated quantities and rates, compared with the sanctioned estimate | When the expected cost or scope changes enough to require renewed approval under the owner's rules |
| Supplementary | Separately measured and priced additional work | New work outside the original sanctioned scope, such as an added compound wall |
| Annual repair | Planned recurring maintenance items and quantities | Yearly upkeep, such as painting, plumbing repairs and minor civil repairs |
A supplementary estimate can go with a revised one. The overrun that triggers a revised estimate differs by department, so check the current approval rules rather than assuming one percentage.
Long wall–short wall and centre-line methods#
Both methods give the same wall and foundation quantities when used correctly; they differ only in how you add up the lengths.
Long wall–short wall: for a rectangular room with uniform sections, measure the two long walls out-to-out and the two short walls in-to-in. If the centre-to-centre dimensions are L and B and the item breadth is b:
- Long-wall length = L + b.
- Short-wall length = B − b.
- Quantity = [2 × (L + b) + 2 × (B − b)] × b × depth or height.
Recalculate b at every footing step. Do not add two full breadths to a centre-to-centre dimension: each end contributes half a breadth.
Centre-line: add the wall centre-line lengths, correct intersecting junctions, and multiply by the section breadth and depth. It is convenient for a simple rectangular plan with identical sections. Separate walls of different thicknesses and check every T-junction so an overlap is not counted twice.
In the example below, L = 4.25 m and B = 3.25 m, so the centre-line length is 2 × (4.25 + 3.25) = 15.00 m. For the 0.90 m-wide trench, long wall–short wall gives 2 × 5.15 + 2 × 2.35 = 15.00 m. Same length, same excavation.
IS 1200 measurement units#
IS 1200 measures earthwork, concrete and brickwork in m³; formwork, plaster, flooring and paint in m²; and reinforcement by weight. Each part has its own deduction rules, so treat this table as a starting map.
| Work | Usual estimating unit | IS 1200 part |
|---|---|---|
| Excavation and filling | m³ (cum) | Part 1 |
| PCC and RCC concrete | m³ (cum) | Part 2 |
| Brickwork | m³; thin walls may use m² with thickness stated | Part 3 |
| Formwork | m² of contact surface | Part 5 |
| Reinforcement | kg or tonne | Part 8 |
| Floor finishes | m² | Part 11 |
| Plastering and pointing | m² | Part 12 |
| Painting | m², with the surface and coating system described | Part 13 |
The BIS civil works measurement committee programme lists the standards and their revision status. Record the edition required by your contract. Our IS 1200 guide to units, openings and deductions covers the trade-specific details. A single “deduct every opening” rule will not work for all items.
Rate analysis: materials + labour + T&P + overheads + profit#
A unit rate is the cost of materials, labour and tools and plant (T&P) for one unit of a defined item, plus overheads and profit. Define the item first: concrete grade or mortar mix, thickness, location, handling, curing and exclusions.
For example, take one m² of 12 mm internal plaster in CM 1:6:
| Component | Illustrative allowance per m² |
|---|---|
| Materials, including the assumed wastage | ₹80 |
| Labour, including application and curing | ₹200 |
| Tools and plant | ₹20 |
| Direct cost | ₹300 |
| Overheads, assumed at 10% of direct cost | ₹30 |
| Profit, assumed at 6% of direct cost | ₹18 |
| Calculated rate | ₹348/m² |
| Rounded teaching rate used below | ₹350/m² |
The 10% and 6% are assumptions for this example, not CPWD rules. A real analysis works from material consumption, delivered prices, labour output and dated wages; the worked rate-analysis guide does that in full.
For scheduled work, start from the applicable CPWD DSR 2023 or state SOR item, with its full description and amendments; the CPWD circular register publishes the correction slips. A schedule rate is not today's local quote, so record how you adjusted it. If the adopted rate already includes overheads and profit, don't add them again.
Full worked example: a small single-room building shell#
A 4 m × 3 m load-bearing room, priced from excavation to roof slab, comes to ₹2,69,293.50 for the listed shell items, or ₹2,82,758.18 with 5% contingency. Dimensions and rates are illustrative assumptions dated 21 October 2026. It is not a structural design or a finished-room price; a structural engineer must specify the real foundation and slab.
1. Record the dimensions and scope#
- Internal room: 4.00 m × 3.00 m.
- Wall thickness: 0.25 m, a round teaching figure (230 mm is common), giving outside dimensions of 4.50 m × 3.50 m and a centre-line perimeter of 15.00 m.
- Wall height above plinth to slab underside: 3.00 m.
- Door opening: 1.00 m × 2.10 m = 2.10 m². Window opening: 1.20 m × 1.20 m = 1.44 m². Total openings: 3.54 m².
- Trench: 0.90 m wide × 0.90 m deep, centred on the walls; no working-space addition in this exercise.
- PCC bed: 0.90 m wide × 0.10 m thick.
- Brick foundation courses: 0.75 m × 0.20 m, 0.50 m × 0.30 m, then a 0.25 m × 0.60 m stem. The stem rises 0.30 m above ground. Below ground, 0.10 + 0.20 + 0.30 + 0.30 = 0.90 m.
- Roof slab: 4.50 m × 3.50 m × 0.125 m, without projections.
- RCC lintels: 1.40 m × 0.25 m × 0.15 m over the door and 1.60 m × 0.25 m × 0.15 m over the window, each with a 0.20 m bearing at both ends.
- Reinforcement: 160 kg provisional allowance for slab and lintels together, pending a bar schedule. It is not a designed steel quantity.
Rates include materials, labour, overheads and profit. Concrete rates exclude steel and formwork, which are priced separately. Each rate is at or above the national and Delhi build-ups in our house cost calculator on that date; costlier cities such as Mumbai run higher. They are not CPWD rates.
2. Work out each quantity#
| Item | Exact measurement | Quantity |
|---|---|---|
| Foundation excavation | 15 × 0.90 × 0.90 | 12.15 m³ |
| PCC 1:4:8 bed | 15 × 0.90 × 0.10 | 1.35 m³ |
| Brickwork in foundation and plinth, CM 1:6 | 15 × [(0.75 × 0.20) + (0.50 × 0.30) + (0.25 × 0.60)] | 6.75 m³ |
| Gross wall masonry | 15 × 0.25 × 3 | 11.25 m³ |
| Opening deduction in masonry | (2.10 + 1.44) × 0.25 | 0.885 m³ |
| Lintel volume, also deducted from masonry | (1.40 + 1.60) × 0.25 × 0.15 | 0.1125 m³ |
| Net wall brickwork, CM 1:6 | 11.25 − 0.885 − 0.1125 | 10.2525 m³ |
| RCC M25 roof slab | 4.50 × 3.50 × 0.125 | 1.96875 m³ |
| Formwork: slab soffit and edges | (4 × 3) + [2 × (4.50 + 3.50) × 0.125] | 14.00 m² |
| Formwork: lintel soffits over the openings, plus both sides | [(1.00 + 1.20) × 0.25] + [2 × (1.40 + 1.60) × 0.15] | 1.45 m² |
| Internal wall plaster, net faces | [2 × (4 + 3) × 3] − 3.54 | 38.46 m² |
| Door jambs and head, plus window reveals | [(2 × 2.10 + 1.00) × 0.25] + [2 × (1.20 + 1.20) × 0.25] | 2.50 m² |
| Ceiling plaster | 4 × 3 | 12.00 m² |
| Total internal plaster, 12 mm CM 1:6 | 38.46 + 2.50 + 12.00 | 52.96 m² |
| External wall plaster, 20 mm CM 1:4 | [2 × (4.50 + 3.50) × 3] − 3.54 | 44.46 m² |
Plaster here deducts every opening in full from both faces and adds the jambs, heads and window reveals once at the internal rate, with no frames or sill finishes. IS 1200 Part 12 uses opening-size bands instead, so follow your contract's rule before billing.
Formwork is the concrete contact area only: the slab soffit over the clear room and the lintel soffits over the clear openings, because the bearings sit on masonry. Quantities keep all decimals so you can check them; round to your contract's convention on a live measurement sheet.
3. Price the quantities and prepare the abstract#
| Priced item | Quantity × illustrative rate | Amount |
|---|---|---|
| Excavation | 12.15 m³ × ₹450/m³ | ₹5,467.50 |
| PCC bed | 1.35 m³ × ₹7,500/m³ | ₹10,125.00 |
| Foundation and plinth brickwork | 6.75 m³ × ₹10,000/m³ | ₹67,500.00 |
| Wall brickwork after deductions | 10.2525 m³ × ₹10,000/m³ | ₹1,02,525.00 |
| RCC slab concrete | 1.96875 m³ × ₹10,000/m³ | ₹19,687.50 |
| RCC lintel concrete | 0.1125 m³ × ₹10,000/m³ | ₹1,125.00 |
| Reinforcement, cut, bent and fixed | 160 kg × ₹85/kg | ₹13,600.00 |
| Formwork | (14.00 + 1.45) m² × ₹550/m² | ₹8,497.50 |
| Internal plaster, reveals and ceiling | 52.96 m² × ₹350/m² | ₹18,536.00 |
| External plaster | 44.46 m² × ₹500/m² | ₹22,230.00 |
| Abstract subtotal: listed shell work | Sum of the ten priced items | ₹2,69,293.50 |
| Contingency, assumed 5% | ₹2,69,293.50 × 0.05 = ₹13,464.675, rounded to paise | ₹13,464.68 |
| Shell budget with contingency | ₹2,69,293.50 + ₹13,464.68 | ₹2,82,758.18 |
Excluded: backfilling and disposal, plinth filling and the floor, damp-proof course, plaster on the plinth and slab edge, waterproofing, doors and windows, sill finishes, painting, services, professional fees and approvals. Replace the provisional steel with the bar bending schedule (BBS) quantity once the slab and lintels are designed.
How the BOQ and abstract fit together#
The measurement sheet shows how each quantity was worked out. The BOQ lists each item's description, unit and quantity, with rate and amount once priced. The abstract of cost adds up the item or trade totals and the stated additions.
Note the drawing revision and measurement reference against each BOQ item. If concrete, steel and shuttering are priced separately, don't add them again under an “RCC package”. For the full workflow, see measurement sheets and BOQ preparation from drawings.
To practise, download the building estimate Excel workings. For a first whole-house budget, the house construction cost calculator Excel recalculates from area, floors, specification and city. It runs on typical quantities, so it does not replace measurements from your drawings.
Common estimating and costing mistakes#
Check every estimate for these eight errors:
- Mixing plot area with built-up area. Record which area a per-sq-ft rate uses, and count every floor once.
- Using inside dimensions as centre-line dimensions. Draw a small section and mark all three: inside, centre-to-centre and outside.
- Keeping the same wall length at every footing step. Long and short lengths change with each course breadth.
- Applying one opening deduction rule to every trade. Masonry, plaster, paint and formwork have different item rules.
- Treating RCC as concrete only. Include reinforcement and formwork separately unless the rate explicitly includes them.
- Comparing rates with different scopes. Labour-only, material-plus-labour and ready-mix supply rates are not interchangeable.
- Double-counting wastage or overheads. Keep purchased-material wastage in the rate build-up where appropriate; measure finished work on its specified basis.
- Using undated rates. Record the location, source date, delivery basis and applicable schedule amendments.
Frequently asked questions#
What is the difference between estimating and costing?#
Estimating works out the quantities of work. Costing puts unit rates on those quantities and adds allowances. Together they give the project budget.
What are the main types of estimate in civil engineering?#
Preliminary, detailed, revised, supplementary and annual repair estimates serve different stages or purposes. Plinth-area and cubical-content methods are common ways to prepare a preliminary estimate.
Which method is better: long wall–short wall or centre-line?#
Both give the same quantity for a simple plan when used correctly. Centre-line calculations are shorter for uniform wall sections. Long wall–short wall calculations make changing foundation breadths easier to inspect. Check junctions and varying thicknesses in either method.
Which IS code is used for estimation and costing?#
The IS 1200 series covers measurement of building and civil engineering works. It does not publish construction prices. Use the applicable part and contract edition for measurement, then CPWD DSR, state SOR or a documented local analysis for the rate.
Can I estimate a house without drawings?#
You can prepare a preliminary budget from built-up area, floors, location and finishes. A detailed estimate needs drawings and specifications. Use the online house construction cost calculator for the first budget and BOQ from your drawings when the design is ready.
Are the example rates current market rates?#
No. They are illustrative rates, set at or above our national and Delhi build-ups on 21 October 2026. Use scoped local quotes or the applicable schedule rates for procurement, tendering or billing.
References and Further Reading
Primary and supporting sources cited in this article.
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