What is the D²/162 formula for steel weight calculation?

The formula Weight (kg/m) = D² ÷ 162 is the standard Indian site shorthand for calculating TMT rebar weight per metre of length, where D is the bar diameter in millimetres. Derivation: W = (π/4) × (D/1000)² × 7850 kg/m³ = π × D² × 7850 ÷ 4,000,000. The exact divisor is 4,000,000 ÷ (π × 7850) = 162.196. The value 162 is a rounded approximation that overestimates by 0.12%, which is acceptable for site BOQ purposes. For greater precision, use D²/162.2 which is within 0.003% of the exact value.

What is the difference between Fe 415, Fe 500, and Fe 500D TMT bars?

Fe 415, Fe 500, and Fe 500D are TMT rebar grades specified in IS 1786:2008. The numbers refer to the minimum yield strength in MPa: Fe 415 has a minimum yield stress of 415 MPa; Fe 500 has 500 MPa; Fe 500D has 500 MPa yield with a higher ductility requirement (higher percentage elongation, better for seismic zones). All three grades use the same steel density of 7850 kg/m³, so the D²/162 weight formula applies equally to all grades — grade selection does not affect weight calculations. Fe 500 and Fe 500D are the most commonly specified grades for structural RCC work in India since the 2000s.

How many kg of steel per metre for a 16mm TMT bar?

For a 16mm diameter TMT bar: W = 16² ÷ 162 = 256 ÷ 162 = 1.580 kg/m. More precisely: W = 16² ÷ 162.2 = 1.578 kg/m, which matches the published Tata Tiscon and SAIL weight chart. For 10mm: W = 100/162.2 = 0.617 kg/m. For 12mm: W = 144/162.2 = 0.888 kg/m. For 20mm: W = 400/162.2 = 2.466 kg/m. For 25mm: W = 625/162.2 = 3.853 kg/m.

Does this steel weight calculator include hook length, lap length, or BBS?

No. This is a simple weight calculator — it multiplies the bar lengths you enter directly by the D²/162 factor. It does not automatically add hook lengths, lap lengths, chair heights, or any other bar bending schedule (BBS) adjustments. For a complete BBS, the total cutting length per bar (including hooks and bends as per IS 2502:1963) must be calculated from the structural drawing first, and then those cutting lengths entered here. A full BBS tool (Tool 10–14 in the Speak Arch QS series) is planned for a future release.

What is the weight of steel in 1 cubic metre of RCC?

The steel content in RCC is specified by the structural engineer as kg/m³ and varies by element type: typical ranges are 80–120 kg/m³ for slabs; 100–180 kg/m³ for beams; 150–250 kg/m³ for columns; 60–100 kg/m³ for footings. The exact value comes from the bar bending schedule (BBS), not from a general rule. For estimating purposes without a BBS, 100 kg/m³ is commonly used as a rough average for mixed RCC framing, but this varies significantly by structural design and building type.

What is the standard length of a TMT bar in India?

IS 1786:2008 specifies that TMT bars are supplied in standard lengths of 12 metres (with a tolerance of ±100 mm for bars up to 10mm diameter and ±200 mm for larger diameters). They are also supplied in random lengths of 4–12 metres. For site BOQ, the cutting length of each bar as calculated from the structural drawing (including hooks) should be used, with additional allowance for lap splices as specified by the structural engineer (typically 40 to 50 times the bar diameter).

Steel Weight Calculator India (TMT)

Calculate TMT steel weight from bar diameter and length — site formula D²/162, bar schedule mode, optional wastage.

Educational BOQ only. Does not include lap length, hooks, or BBS from structural drawings. Educational procurement estimate.

How to use this calculator

Use quick calc (dia × length × qty) or bar schedule rows.
Select Fe grade for reference (display only).
Set wastage % for cutting scrap.
Calculate total kg and per-metre weights.
Export CSV for site records.

For RCC volumes, use the concrete volume calculator.

Units

Fe grade (FAQ only — weight is grade-independent)

Wastage

₹ / kg (optional cost)

Typical 2025 site rate: Fe 500 ₹58–75/kg (varies by market).

kg / m (D²÷162.2)

Bar schedule Add one row per bar group · Enter to move to next field

Mark / desc Dia (mm) Length (m) Qty kg/m Row kg

Bar schedule — computed weights

Mark	Dia (mm)	Length	Qty	kg/m	kg/bar	Row kg

Constants & formula reference

Formula: W (kg) = D² ÷ 162 × L × n — where D = diameter in mm, L = length in m, n = number of bars.

Displayed divisor: 162 — industry standard shorthand used in India. Overestimates by 0.12% vs exact.

Internal calculation: D² ÷ 162.2 (within 0.003% of exact derivation).

Exact derivation: Divisor = 4,000,000 ÷ (π × 7850) = 162.196. Source: Excel ROUND BAR sheet formula: 0.7854 × D² × 7.85 / 1000.

Steel density: 7850 kg/m³ — applicable to all IS 1786:2008 Fe grades (415, 500, 500D). Grades differ by yield strength and ductility only.

IS 1786:2008: High Strength Deformed Steel Bars for Concrete Reinforcement — specifies Fe 415, Fe 500, Fe 500D, Fe 550, Fe 550D grades.

Standard bar length: 12 m (IS 1786:2008 Clause 9). Random lengths 4–12 m also supplied.

Frequently asked questions

What is the D²/162 formula and how is it derived?

W (kg/m) = D² ÷ 162, where D is diameter in mm. Derived from: W = π/4 × (D/1000)² × 7850 kg/m³ = D² × π × 7850 / 4,000,000. The exact divisor is 4,000,000 / (π × 7850) = 162.196. The value 162 is the rounded standard used in India — it overestimates by 0.12%, which is within BOQ tolerance. For precision use 162.2 (within 0.003% of exact).

Fe 415 vs Fe 500 vs Fe 500D — weight difference?

None. All three grades in IS 1786:2008 use steel density of 7850 kg/m³. The numbers refer to minimum yield strength (MPa). Fe 500D adds higher ductility requirements (useful in seismic zones). Grade selection does not change the D²/162 weight calculation.

Weight of 16mm TMT bar per metre?

W = 16² ÷ 162.2 = 1.578 kg/m (matches Tata Tiscon and SAIL published charts). Using D²/162: 1.580 kg/m (0.12% higher). For a 12m standard bar: 1.578 × 12 = 18.94 kg per bar.

Does this include hooks, laps, or BBS adjustments?

No. Enter the total cutting length per bar (including hook allowances as per IS 2502:1963) to get accurate results. This tool multiplies your input length directly by D²/162. Lap lengths, chair heights, and stirrup hook extensions must be included in the length you enter. A full BBS tool is planned in the Speak Arch QS series.

How many kg of steel per m³ of RCC?

Varies by element type: slabs 80–120 kg/m³; beams 100–180 kg/m³; columns 150–250 kg/m³; footings 60–100 kg/m³. These are indicative ranges — actual quantities come from the BBS. Do not use these ranges for procurement without a structural engineer’s BBS.

What is the standard TMT bar length in India?

IS 1786:2008 (Clause 9) specifies standard length of 12 m, with tolerance ±100 mm (≤10mm dia) or ±200 mm (>10mm dia). Random lengths 4–12 m are also supplied. For BOQ purposes, always use the cutting length from the structural drawing, not the standard 12 m supply length, unless you are estimating number of bars to purchase.