What does a construction calculator need to do in India?

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Indian building maths mixes units: rooms in feet, drawings in millimetres, sand and aggregate in cft or brass (1 brass = 100 cft = 2.83 m³) and cement in 50 kg bags. The common sums: bricks for 9-inch walls, cement and sand for 1:6 mortar, M20 nominal mix at 8.06 bags per m³, and 190 mm stair risers.

What units and rules does Indian building work use?

Two systems at once. Plots and rooms are talked about in feet and square feet, structural drawings are in millimetres, concrete is designed in cubic metres, and sand, aggregate and murum are bought by the cubic foot (cft) or the brass, which is 100 cft. Cement comes in 50 kg bags: IS 269 says “The net quantity of cement per bag shall be 50 kg”. A calculator for Indian work has to move between all of these without a slip.

The rules come from three places. Bureau of Indian Standards codes cover materials and workmanship: IS 456 for concrete, IS 1077 for bricks and IS 2212 for brickwork. The National Building Code of India 2016 and the Model Building Bye-Laws 2016 from the Ministry of Housing and Urban Affairs set out room heights, stairs and other planning rules. Your state's rules and your local body (municipal corporation, municipality, panchayat or development authority) decide what applies to a building; the bye-laws are a model for them, and some are stricter. This page and the app don't make work compliant.

How do I convert cft, brass and cubic metres?

Multiply cubic metres by 35.315 to get cft, and divide cft by 100 to get brass. One foot is exactly 0.3048 m, so these follow:

UnitIn cubic feetIn cubic metres
1 cubic metre (m³)35.315 cft1 m³
1 cubic foot (cft)1 cft0.0283 m³ (28.3 litres)
1 brass100 cft2.832 m³
1 bag of cement, 50 kgabout 1.23 cftabout 0.0347 m³, at 1440 kg/m³
1 cubic yard27 cft0.765 m³

So 3 brass of sand is 300 cft, or 300 ÷ 35.315 = 8.495 m³. The brass is a trade unit, used most in Maharashtra and the states around it; Maharashtra's own minor-mineral royalty rates are quoted per brass. To turn a volume into tonnes you need the material's weight: IS 875 (Part 1) gives dry, clean sand as 1540 to 1600 kg/m³, so a brass of dry sand weighs 2.832 × 1.54 to 1.60 = 4.36 to 4.53 tonnes. Damp sand bulks up and weighs differently, so ask the supplier. The sum is in cubic metres to tonnes.

Free cft, brass and m³ converter: it opens on 1 brass. Type 3 and read 8.495 m³.

How many bricks and cement bags for a 9-inch wall?

Count the bricks by the face of the wall, two layers for a 9-inch wall and one for a 4½-inch wall, then work out the mortar. With IS 1077's modular bricks, 190 × 90 × 90 mm, and 10 mm joints, a 9-inch wall takes 100 bricks per m² (9.29 per sq ft). Worked example: a wall 20 ft long and 10 ft high with a 3 × 7 ft door, in 1:6 mortar.

  1. Area: 20 × 10 − 3 × 7 = 179 sq ft, which is 16.63 m².
  2. Bricks: 16.63 × 100 = 1663, and 1663 × 1.05 = 1746.2, so order 1747.
  3. Mortar: 0.000461 m³ a brick (0.2 × 0.1 × 0.1 − 0.19 × 0.09 × 0.09), so 0.767 m³ wet and 0.767 × 1.33 = 1.020 m³ dry.
  4. Cement: 1.020 ÷ 7 × 1440 = 210 kg, 4.20 bags, so buy 5. Sand: 1.020 × 6 ÷ 7 = 0.874 m³, which is 30.9 cft.

Traditional 9 × 4½ × 3 in bricks (230 × 115 × 75 mm) come to 98 per m² in a 9-inch wall. The method, the per-m³ figures and how they compare with CPWD's analysis of rates are in the brick calculator for India.

Free brick calculator: it opens on the wall above. Change the length, height and doors, pick 4½ inch for a partition and 1 : 4 for its mortar.

How many cement bags for an M20 roof slab?

Work out the slab's wet volume, multiply by 1.54 for the dry materials, and split it 1 : 1.5 : 3. IS 456 allows nominal mix only up to M20 and sets M20 as the lowest grade for reinforced concrete. A room 12 × 10 ft with a 5 in slab:

  1. Volume: 12 × 10 × 5 ÷ 12 = 50 cft, which is 1.416 m³.
  2. Dry materials: 1.416 × 1.54 = 2.180 m³, in 1 + 1.5 + 3 = 5.5 parts.
  3. Cement: 2.180 ÷ 5.5 × 1440 = 571 kg, 11.42 bags, so buy 12.
  4. Sand: 2.180 × 1.5 ÷ 5.5 = 0.595 m³ = 21 cft. Aggregate: 1.189 m³ = 42 cft.

Per cubic metre that is 8.06 bags, 0.42 m³ of sand and 0.84 m³ of aggregate, close to CPWD's 0.400 tonne, 0.425 m³ and 0.850 m³. Add the beams and the slab's bearing on the walls before you order. The grades, IS 456 Table 9 and the sources are in the concrete mix calculator.

Free concrete mix calculator: it opens on the 12 × 10 ft slab above in M20. Pick M15 or M10 for plain concrete, or switch to The volume to type cubic metres or cft.

How do I convert mm to feet and inches?

Divide millimetres by 25.4 for inches, then take out whole feet in twelves. One foot is 304.8 mm, so a 10 ft room is 3048 mm. The other way, a 230 mm wall is 230 ÷ 25.4 = 9.06 in, which is the “9-inch” wall, and a 3000 mm floor-to-floor height is 118.11 in, or 9' 10 1/8". The steps and a table are in mm to feet and inches, and the feet and inches calculator converts and adds lengths both ways. Area works the same way squared: 1 m² is 10.764 sq ft.

What are the stair rules for a house in India?

For a one- or two-family house, the National Building Code 2016 (Part 3, clause 12.18.1) allows risers up to 190 mm, treads of at least 250 mm without the nosing and 12 risers a flight, with a stair at least 1.0 m wide and 2.2 m of headroom. The Model Building Bye-Laws 2016 (clause 4.17) give the same figures for residential buildings. Your local bye-laws can be stricter: Delhi's Unified Building Bye-Laws cap risers at 150 mm in low-rise housing. Habitable rooms must be at least 2.75 m high (MBBL clause 4.3.1.1).

Worked example: a floor-to-floor height of 3000 mm with 250 mm treads.

  1. Risers: 3000 ÷ 190 = 15.8, so at least 16 risers of 3000 ÷ 16 = 187.5 mm.
  2. Flights: 16 risers is more than 12, so it needs a landing. Two flights of 8, each rising 1500 mm.
  3. Going: 8 risers have 7 treads, so 7 × 250 = 1750 mm of going in each flight, plus the landing.
  4. Under Delhi's 150 mm cap: 3000 ÷ 150 = 20 risers, two flights of 10.

Without Riser Limited ticked, the app picks the riser count from a comfort rule (riser = (600 − going) ÷ 2) and gives 9 risers of 166.7 mm for the same flight, which also passes. Its amber riser warning fires above 190 mm, the same as India's limit, but its going check (150 to 450 mm) is wider than India's 250 mm minimum tread, so check that yourself. The free stair calculator on this site does the same sums in a browser.

Which MeisterCalc calculators suit Indian work?

MeisterCalc is an Android app with 16 construction calculators, each drawing the job as you type. It works in millimetres, or in feet, inches and sixteenths once you set Settings ▸ Units ▸ Default units to Imperial (ft/in), and every calculation runs on the phone, so it works with no signal on site. For Indian work:

  • Stairs (free): risers, treads, stringer length and the stairwell opening, one flight at a time.
  • Concrete (free): slab and footing volumes in m³ and litres, with 10% to order. Multiply by the mix figures above for cement, sand and aggregate.
  • Check Square (free): the diagonal that squares a plot or a column layout.
  • Dumpy Level: height of instrument and reduced levels in metres. Gravel and Soil: cubic metres to tonnes at the density you type. Triangles and Pitch for slopes and sloping roofs.

The app doesn't count bricks or split concrete into cement, sand and aggregate, and it shows volumes in m³, not cft or brass. The free calculators on this page do those. It runs on Android 7.0 or later. For other countries' rules and other trades, see calculators by trade and country.

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Codes and sources

Checked on 1 November 2026. The drawings, your structural engineer and your local body decide what a building needs; the figures here are quoted so you can check them.

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