Short answer
What is the centre line method of estimation? The centre line method takes the length of wall along its centre line, multiplies it by the wall's thickness and height, and then corrects for the junctions where walls meet. It is a practice method, not a clause of IS 1200. The copies of IS 1200 read for this page are older editions, so ask your estimator for the current measurement rules and a written quantity sheet.
On this page (8)
Before a house is built, someone has to say how much brickwork, plaster, concrete and earthwork it needs. The estimator measures the plan. For walls, the most common quick method is the centre line method: measure around the middle of the walls, then multiply. This page explains the method, what the older Indian measurement standard said about the same work, and what to ask for. It gives no rate, no price and no brick count per square foot.
What is the centre line method?
The idea is simple. A wall’s length is easiest to read from the middle of the wall, because the outer and inner faces each change at the corners. So the estimator:
- Measures the total length of the centre line of every wall, going round the building and across the cross walls.
- Multiplies that length by the wall’s thickness, to get the area on plan.
- Multiplies by the height (or the depth, for a foundation trench), to get the volume.
- Corrects for the junctions, where a wall meets another wall and the centre line is counted twice.
- Deducts the openings, such as doors and windows, that the wall does not contain.
This is a practice method. It works for a wall of even thickness. For a wall that changes thickness, or for a building with many junctions, the estimator measures each part separately.
A worked example
Take a small room with walls on a 4.30 m by 3.30 m centre line, 0.3 m thick and 3.0 m high. The arithmetic is:
- Centre line length: 2 × (4.30 + 3.30) = 15.20 m.
- Area on plan: 15.20 m × 0.3 m = 4.56 m2.
- Volume: 4.56 m2 × 3.0 m = 13.68 m3.
This example shows the arithmetic only. It is not a quantity for any house, and the openings and junctions of a real house change it.
What does IS 1200 say?
IS 1200 is the Indian series of methods of measurement for building and civil engineering works. Its parts give the rules an estimator follows, for example for brickwork, earthwork and plastering.
The copies of IS 1200 read for this page are older editions. The brickwork part read is the 1976 edition, and the earthwork part is the 1992 edition. Newer editions dated 2026 have been issued, and those were not read for this page. So this page does not quote a clause as the rule in force.
The older brickwork edition does say two things that are useful to know:
- All work is measured net, as fixed in place, to the nearest 0.01 m, 0.01 m2 and 0.01 m3 (clause 2.3).
- No deduction is made for an opening up to 0.1 m2 in area (clause 4.1.4(b)). Openings over that size are not covered by the exemption.
Ask your estimator which edition the quantity sheet follows, and check these two points against the current part.
| Point | Older IS 1200 edition read for this page | Current edition |
|---|---|---|
| Rounding to 0.01 m, 0.01 m2 and 0.01 m3 | Part 3 (1976) clause 2.3 | not read |
| No deduction for openings up to 0.1 m2 | Part 3 (1976) clause 4.1.4(b) | not read |
| Footings counted in general brickwork | Part 3 (1976) clause 3.1.2(a) | not read |
| The centre line method | Not described in words | not read |
The older edition does not describe the centre line method in words. Its cavity-wall rule measures along the centre plane of the cavity, which is a different thing. Treat the method as practice, and the IS 1200 rules as the frame it must fit.
Where do the quantities go?
The centre line method is used for the rough quantities that go into a bill of quantities. It gives the brickwork volume and the foundation trench volume. The bill of quantities page explains how those quantities are listed.
What mistakes should I avoid?
- Counting a junction twice. Two walls that meet share a length of centre line. The junction correction is where many estimates go wrong. Ask the estimator to show the correction. This is practice.
- Using one thickness for every wall. An outer wall and a partition are often different. Measure each thickness separately. This is practice.
- Deducting every opening. The older brickwork rule gives no deduction for small openings. Check the current rule before you use it. This is practice, backed by the older clause.
- Trusting a junction rule from the web. Web pages give different junction rules. None of them is a clause of IS 1200 read for this page. Ask for the rule the estimator uses, in writing. This is practice.
- Mixing units. Keep to metres, square metres and cubic metres, rounded in the same way on every line. This is practice.
Frequently asked questions
Is the centre line method in IS 1200?
The copies read do not describe it by that name. It is a practice method, used with the measurement rules.
Why measure along the centre line?
The centre line gives one length for each wall, without the corners of the outer and inner faces. The junctions are then corrected.
Should I use it for my house?
It is a common method for a quick estimate. A final quantity sheet should come from the drawings and the estimator’s rules, and it should be checked.
What should I ask my estimator for?
A written quantity sheet with the method, the edition of the measurement rules, the junction correction and the deductions for openings.
Related guides
- What is a bill of quantities (BOQ) for a house?
- How excavation is measured: trench volume, working space, lead, lift
This guide is general information. Read the disclaimer. Your estimator and engineer produce the quantities for your house, and the drawings are the reference.
Sources
- IS 1200 (Part 3):1976, Method of Measurement of Building and Civil Engineering Works, Part 3 Brickwork (third revision): clauses 2.3 (rounding to 0.01 m, 0.01 m2 and 0.01 m3), 3.1.2(a) (footings in general brickwork), 4.1 and 4.1.4(b) (no deduction for openings up to 0.1 m2). Older edition, reaffirmed 2002; the newer 2026 edition was not read.
- IS 1200 (Part 1):1992, Method of Measurement, Part 1 Earthwork (fourth revision): clause 2.3 (measurement to 0.01 m, m2 and m3) and foreword (rounding). Older edition, reaffirmed 2002; the newer 2026 edition was not read.
Change log
- : Added Related guides link to newly published article(s): how-excavation-for-a-house-foundation-is-measured-trench-volume-working-space-lead-and-lift. No other text changed. Approved by the reviewing engineer.
General information only. It is not a structural design or professional advice. Ask a licensed structural engineer or architect to check your plans and site.