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RCC Slab, Beam and Column Calculator

Steel bar by bar and concrete by volume for one slab, beam or column, from your drawing's sizes.

Construction● Free Formula shown Rates dated
Quick Answer

Steel for an RCC member = number of bars × cutting length × bar weight per metre. The weights come from IS 1786 (8 mm 0.395, 10 mm 0.617, 12 mm 0.888 kg/m) and a closed stirrup is 2 × (inside width + inside depth) + 24 × bar size long, per IS 2502. A 3.5 × 4.5 m slab, 125 mm thick, with 10 mm bars at 150 mm and 8 mm at 200 mm, takes about 100 kg of steel and 2 m³ of concrete (17 bags of cement in M20). Enter the sizes from your drawing below.

Rates checked Jul 2026. Source: IS 1786:2008 High strength deformed steel bars and wires for concrete reinforcement: Table 1 (nominal mass per metre) and Table 2 (mass tolerance); Public.Resource.Org copy of the BIS standard.

0.888 kg/ma 12 mm TMT bar, IS 1786
24dhook allowance on a closed stirrup, IS 2502
5%steel wastage, CPWD 2023
about 100 kgsteel in the 3.5 × 4.5 m sample slab

Part of the system: Slab casting day. Steps, checks and a free printable page.

Guides: Bar bending schedule to order, Check a TMT steel delivery, Concrete cube test record, Cover blocks and chairs, Slab curing days and props.

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The Formula

Steel (kg) = Σ (bars × cutting length × IS 1786 kg/m) × 1.05; stirrup length = 2(A + E) + 24d

Bars in a slab: (span − 2 × cover) ÷ spacing + 1, each as long as the other side less two covers. A and E are the stirrup's inside sizes: member size less two covers and two stirrup diameters. The 1.05 is CPWD's 5% wastage on reinforcement. Concrete is length × width × depth, then the same nominal-mix arithmetic as the concrete calculator (dry volume × 1.54, split by the mix ratio).

Weight per metre of TMT bar (IS 1786)8 mm 0.395 kg/m, 10 mm 0.617, 12 mm 0.888, 16 mm 1.58, 20 mm 2.47, 25 mm 3.85, 32 mm 6.31.8 mm0.395 kg/m10 mm0.617 kg/m12 mm0.888 kg/m16 mm1.58 kg/m20 mm2.47 kg/m25 mm3.85 kg/m32 mm6.31 kg/m
Weight per metre of TMT bar (IS 1786). Weight goes with the square of the diameter. Go from 8 mm to 16 mm and each metre weighs four times as much.

Assumptions

  • Bar weights per metre are the nominal masses in IS 1786:2008 Table 1, not d²/162 (the two differ by under 0.5%)
  • Stirrups and column ties are closed links with hooks, IS 2502:1963 Table VIII shape A: length 2(A + E) + 24d, with A and E the inside sizes
  • Cover is measured to the outside of the stirrup, as IS 456 clause 26.4.1 defines it (cover to all steel, including links)
  • Steel wastage is 5%, the figure in CPWD Analysis of Rates 2023 item 5.22 for reinforcement
  • Concrete grades are nominal volumetric mixes (M15 1:2:4, M20 1:1.5:3, M25 1:1:2) with a 1.54 dry-volume factor and a 50 kg cement bag = 0.0347 m³; cement +3%, sand +10%, aggregate +5% wastage
  • Concrete volume is not reduced for the space the steel takes up, which is the usual measurement convention
  • Not added: laps, cranked (bent-up) bars, extra bars over supports, chairs and binding wire
How the steel total is builtFour steps: count the bars, cutting length with stirrups at 2(A + E) + 24d, weight as bars times length times kg per metre, add 5% wastage.1Count the bars: (span − 2 × cover) ÷ spacing + 12Cutting length: the other side less two covers;stirrups 2(A + E) + 24d3Weight: bars × length × kg per metre4Add 5% wastage (CPWD)
How the steel total is built.

TMT bar weight per metre (IS 1786)

Nominal mass per metre from IS 1786:2008 Table 1, with the weight of a standard 12 m bar and the mass tolerance the standard allows on a batch.

Bar sizekg per metreOne 12 m barBatch tolerance
8 mm0.3954.74 kg±7%
10 mm0.6177.40 kg±7%
12 mm0.88810.66 kg±5%
16 mm1.5818.96 kg±5%
20 mm2.4729.64 kg±3%
25 mm3.8546.20 kg±3%
32 mm6.3175.72 kg±3%

IS 456 Table 16 nominal cover minimums, for the cover inputs: mild exposure 20 mm, moderate 30 mm, severe 45 mm, very severe 50 mm, extreme 75 mm. Columns: at least 40 mm (clause 26.4.2.1). Footings: 50 mm (26.4.2.2).

Minimum nominal cover by exposure (IS 456 Table 16)Mild 20 mm, moderate 30 mm, severe 45 mm, very severe 50 mm, extreme 75 mm.Mild20 mmModerate30 mmSevere45 mmVery severe50 mmExtreme75 mm
Minimum nominal cover by exposure (IS 456 Table 16). Columns need at least 40 mm and footings 50 mm, whatever the exposure.

Worked Examples

Roof slab 3.5 × 4.5 m, 125 mm thick

  1. Main bars, 10 mm @ 150: (4,500 − 2 × 20) ÷ 150 + 1 = 30 bars, each 3,460 mm
  2. Distribution bars, 8 mm @ 200: (3,500 − 2 × 20) ÷ 200 + 1 = 18 bars, each 4,460 mm
  3. Steel: 103.8 m × 0.617 + 80.3 m × 0.395 = 95.8 kg; with 5% wastage 100.5 kg
  4. Concrete: 3.5 × 4.5 × 0.125 = 1.969 m³; in M20 that is 17 bags of cement, 32.1 cft of sand and 61.3 cft of aggregate
  5. Material cost: ₹15,043 to ₹20,798 (as of Jul 2026)

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Beam 4 m long, 230 × 400 mm

  1. Longitudinal bars: 3 bottom + 2 top, 12 mm, each 4,000 − 2 × 30 = 3,940 mm: 10.5 + 7 kg
  2. Stirrup inside size: 400 − 2 × 30 − 2 × 8 = 324 mm by 230 − 2 × 30 − 2 × 8 = 154 mm
  3. Stirrup length: 2 × (324 + 154) + 24 × 8 = 1,148 mm; 27 stirrups weigh 12.2 kg
  4. Steel: 29.7 kg, with 5% wastage 31.2 kg (81 kg per m³ of concrete)
  5. Concrete: 0.368 m³, 4 bags of cement in M20; material cost ₹3,759 to ₹5,074 (as of Jul 2026)

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Four columns 230 × 300 mm, one 3 m lift

  1. Concrete: 3 × 0.23 × 0.3 × 4 = 0.828 m³
  2. Vertical bars: 16 × 3 m = 48 m × 0.888 = 42.6 kg
  3. Ties: inside 204 × 134 mm, each 2 × (204 + 134) + 24 × 8 = 868 mm; 21 per column, 84 in all, 28.8 kg
  4. Steel: 71.4 kg, with 5% wastage 75 kg; cement 7 bags in M20
  5. Material cost: ₹8,078 to ₹10,909 (as of Jul 2026)

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Rates & Model Data Used

Every number below is a range with a date — material prices in India move quickly, so always check the "as of" month before relying on a figure.

ItemRate / valueAs ofNote
Cement (OPC 43 grade)₹320–415 / bag (50 kg)Jul 2026Per 50 kg bag as listed by retail sources; no dealer page in the set states a tax basis, so GST-inclusive at 18% is inferred, not quoted — a strong inference, but an inference, and the reason this is medium rather than high. Re-baselined 2026-07-24: the band was ₹340–410 at high confidence, resting on two content farms plus official anchors that turn out to be estimating conventions rather than market evidence. Grade does not move the retail price. On the only dated price list found that quotes both grades (Bangalore, 6 Jul 2026, seven brands), five of seven price OPC 43 and OPC 53 identically to the rupee, the mean difference is −₹1.79/bag and the median is exactly zero — so OPC 53 carries this same band. No Indian government schedule prices the grades apart either: CPWD DAR 2023 carries a single grey-cement rate of ₹5,156/t and lets estimators substitute ordinary, pozzolana or slag against it, and WPI has no OPC 53 series. That is an accounting convention rather than proof about the market, but not one official source in the country supports paying more for 53. What does move the price: brand ₹75/bag (Maha ₹335 against UltraTech ₹410, same list, same day — 22%) and city ₹35/bag (ACC OPC 53 ₹395 Bangalore against ₹360 Hyderabad, 570 km apart). Against those, grade at zero is a rounding error. Bulk orders of 100+ bags take another ₹10–20/bag off. GST moved 28% → 18% on 22-09-2025 (CBIC Notification 9/2025, heading 2523, which names slag cement expressly); any bag price published before Oct 2025 is on the old regime — multiply by 1.18/1.28 = 0.9219, a 7.8% fall, before comparing. Cost check: ₹320 incl. = ₹5,424/t ex-GST against CPWD's ₹5,156/t ex-GST ex-carriage bulk Delhi (Apr 2023) = +5.2%, which leaves about 5% for carriage plus the whole dealer chain — thin, and only plausible near a plant, which is what a value brand in a southern clinker market is. Cement WPI has moved between −3% and +2% since Apr 2023, so no inflation adjustment to that anchor is warranted. Declared weaknesses: the ₹400–415 ceiling is two lines on one Bangalore page (verbatim-confirmed by three independent readers, uncorroborated elsewhere — the one corroborator refused connection), first-hand retail evidence is two southern cities plus one Delhi single-brand list, and July is near the seasonal trough since cement softens through the monsoon and firms in the Jan–Mar infrastructure season. Treat as a national indicative band and check your own market.
River sand₹60–110 / cftJul 2026Re-anchored 2026-07-25: the three content farms (HouseYog, Civiconcepts, Varna Homes) that used to back this band are struck; it now rests on two government schedules read firsthand — but be clear about what they anchor. CPWD DAR 2023 applies coarse sand (zone III, natural) at ₹1,450/cum throughout its own concrete and mortar rate analyses = ₹41/cft ex-GST, ₹43/cft incl. 5% GST (a stray basic-rate index line at ₹285/cum is an anomalous layout artifact, not the applied rate; the '₹1,450 = spirit/air-compressor' reading is a coincidental-value misread — the operative applied rate is ₹1,450). Maharashtra PWD SSR 2022-23 (p.541) gives natural/VSI/artificial sand ₹1,670/cum = ₹47/cft, crushed ₹1,200/cum = ₹34/cft, screened natural (plaster) ₹1,781/cum. So the government evidence pins an EX-GST, EX-CARRIAGE, AT-SOURCE rate of ~₹41–47/cft (~₹43–50 incl. GST at yard) — and that is ALL it pins. The ₹60 floor is that yard rate plus a minimum ~₹15/cft lead (matching delivered Delhi ≈ ₹50–65); it is lowered from ₹70, which came only from the now-struck per-tonne blog quotes. The ₹110 ceiling is deliberately NOT re-sourced — no primary or retail anchor exists above ₹70 now — and the whole upper half is extrapolation (source rate + heavy lead + retail margin + documented 30–50% mining-ban and monsoon spikes). That is exactly why this is medium, not high, and why the carriage bridge from source to delivered is a fitted, unverified step, disclosed as such. Do not cite the schedules as proof of the delivered band; they anchor only the floor. South metros (Bangalore/Chennai/Hyderabad) sit at the ceiling and above, North plains and near-river Maharashtra at or below the floor; transport adds ₹15–40/cft. Unit exactness is the classic sand failure: confirm cft vs brass (1 brass = 100 cft = 2.83 cum) vs tonne vs truckload and whether transport is in the quote; 1 cum = 35.3147 cft. Density (resolved, unchanged): 22–24 cft/t (1,470–1,600 kg/m³) from IS 2386 Pt III, classical tables and trade 1 brass ≈ 4.5 t — do NOT cite IS 383 for density, it grades aggregate, it does not weigh it. GST 5% (natural sand HSN 2505), asserted from the standing schedule and NOT re-verified against a CBIC notification this pass — flagged. State sand portals (Telangana TGMDC, AP) are JS booking apps that expose no static notified rate.
Coarse aggregate (20 mm)₹35–55 / cftJul 2026Delivered retail; ex-supplier ₹700–900/tonne (~₹32–41/cft; 1 cft ≈ 45 kg). Long lead distances push delivered price toward ₹68/cft. 10 mm runs ₹2–5/cft above 20 mm. Official anchor (verified 2026-07): CPWD DAR 2023 20 mm single-size ₹1,425/cum = ₹40.3/cft ex-GST ex-carriage (Delhi, Apr 2023) — mid-band once carriage and GST are added; lifted to high. Primary-minerals WPI +12% YoY (Apr 2026): extraction costs are rising.
TMT steel bars (Fe500/Fe500D)₹55–68 / kgJul 2026Retail delivered, small quantities. Trade/brand list price runs ₹48–58/kg (Fe500D ₹52–58; base primary-mill ~₹49,000/tonne, NCR, Jul 2026). 8 mm bars carry ₹1–3/kg premium over 12–16 mm; premium brands +5–8%. Monsoon (Jul–Sep) is the soft season. Official anchors (verified 2026-07): CPWD DAR 2023 Fe500D ₹55.5/kg ex-GST (+18% GST = ₹65.5 — brackets this band almost exactly); Clause 10CA Dec 2025 ₹45.8/kg ex-primary-producer; WPI mild steel +1.7% over 24 months — lifted to high. Caution: basic-metals WPI firmed +7% YoY by Apr 2026; recheck quarterly.

How to Use This Calculator

  1. Pick the member and count. Choose slab, beam or column. If the drawing has six identical beams, enter 6 instead of running it six times.
  2. Copy the sizes from the drawing. Use the overall sizes and the bar marks as written, e.g. 10 mm @ 150 c/c for a slab or 3-12 mm bottom for a beam.
  3. Set the cover. Use the cover shown on the drawing. If it is silent, ask your engineer; the IS 456 minimums are listed under the bar-weight table.
  4. Check the bar schedule. Compare the table with your contractor's BBS. Add laps and cranked bars from the drawing on top, then print the schedule.

Frequently Asked Questions

How do I calculate the steel in a slab?
Count the bars in each direction as (span − 2 × cover) ÷ spacing + 1, multiply by each bar's length, then by its weight per metre. For a 3.5 × 4.5 m slab with 10 mm bars at 150 mm and 8 mm at 200 mm, that comes to 95.8 kg, or 100.5 kg with 5% wastage.
What is the cutting length of a stirrup?
IS 2502 gives 2 × (A + E) + 24d for a closed rectangular link, where A and E are the inside sizes and d is the bar size. A 230 × 400 mm beam with 30 mm cover and 8 mm stirrups has inside sizes of 154 × 324 mm, so each stirrup is 2 × (154 + 324) + 192 = 1,148 mm.
Why does this use 0.888 kg/m for 12 mm instead of d²/162?
0.888 kg/m is the nominal mass in IS 1786 Table 1, the figure a mill's bars are checked against. d²/162 gives 0.889, so the difference is tiny; the table value is the official one.
How much steel goes into one cubic metre of RCC?
It depends on the design, which is why this calculator works bar by bar. In the three examples on this page it comes to about 49 kg/m³ for the slab, 81 kg/m³ for the beam and 86 kg/m³ for the columns. Treat these as takeoff results; the design sets the real figure.
Does the calculator include laps?
No. Laps depend on where the bars are joined and on the lap length your engineer specifies, so take them from the drawing and add them. Columns lap at each floor, so add one lap per vertical bar per lift.
Can I use this to decide bar sizes or slab thickness?
No. Bar sizes, spacing, depth and cover come from a structural design by a qualified engineer. This page only measures what the drawing already specifies, so you can check a quantity, a bar schedule or a material order.
Why is my contractor's steel figure higher?
Usually because a real bar schedule includes laps, cranks, extra top bars over supports, chairs and closer stirrups near the supports. Ask for the BBS and compare it line by line with the table here.
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Sources & Limitations

What this calculator does not model

  • A quantity takeoff from an existing drawing, not a structural design or check. A qualified engineer sets every size, bar and cover
  • Laps, cranked bars, extra support bars, chairs and binding wire are not included
  • One stirrup spacing per member; zones with closer spacing need a separate run
  • Rectangular members only; circular columns, flat slabs, footings and staircases calculate differently
  • Material cost excludes shuttering, labour, bending and transport