OnlineCalculator360
Result
How the Steel Weight Calculator Works
This calculator applies the standard D²/162 formula to compute the weight per metre of a steel bar from its diameter, then multiplies by the total bar length (bar length × number of bars) to give total weight in both kg and tonnes. The formula is derived from first principles using the density of structural steel (7850 kg/m³) as specified in IS:1786-2008, making it the same method used by TATA Tiscon, JSW Neosteel, SAIL, and other Indian TMT manufacturers in their published weight tables.
The D²/162 Formula Explained
The D²/162 formula is a simplified constant-factor version of the volume × density calculation for a solid steel cylinder. The full derivation: volume of a 1 m length of bar = π/4 × (D/1000)² m³, where D is diameter in mm. Weight = volume × density = π/4 × (D/1000)² × 7850 kg/m³ = D² × 0.006165 kg/m, which is approximately D²/162. The constant 162 is derived from 1 ÷ 0.006165 ≈ 162.2. This constant holds for any standard structural steel with a density of 7850 kg/m³. The formula assumes a perfectly circular solid cross-section with no voids — valid for TMT bars and plain MS bars. Hollow sections (square or circular hollow section steel) require a different formula. For quick reference: a 10 mm bar weighs 0.617 kg/m, a 16 mm bar weighs 1.580 kg/m, and a 20 mm bar weighs 2.469 kg/m.
Standard TMT Bar Grades in India
IS:1786-2008 defines five grades of TMT (Thermo-Mechanically Treated) reinforcement bars for Indian construction: Fe415, Fe500, Fe500D, Fe550, and Fe600. The number refers to the characteristic yield strength in N/mm² (MPa). All five grades have identical density (7850 kg/m³), so the D²/162 formula gives the same weight for a given diameter regardless of grade. The difference between grades is mechanical performance: Fe500 and Fe500D are the most commonly specified grades in residential construction across India. Fe500D has a higher elongation at break (minimum 16% vs 12% for Fe500) and superior bendability, making it the preferred choice in seismic zones III, IV, and V under IS:13920. Fe600 is used in high-rise and heavy industrial structures where section sizes need to be minimised. For most residential construction, specifying Fe500D from a BIS-certified manufacturer is the recommended practice.
When to Use This Calculator
Use this calculator for three main tasks: estimating steel quantity for a purchase order (multiply total bar weight by current market price per tonne to get material cost), verifying that a contractor's steel quantity statement is reasonable before payment, and cross-checking the bar bending schedule (BBS) prepared by your structural engineer. For a rough project estimate before detailed drawings are available, multiply built-up area by 4–5 kg/sq ft as a rule of thumb for residential RCC construction. For structural design — deciding how much steel is actually required in a beam, column, or slab — use our Rebar Quantity Calculator or consult a structural engineer. Also see our Concrete Volume Calculator for estimating concrete alongside steel quantities, and our Construction Cost Calculator for overall project budgeting.
Steel Bar Weight Formula
The D²/162 formula is the industry-standard method used in India for calculating TMT and MS steel bar weights. It derives from steel's standard density of 7850 kg/m³ and the geometry of a solid circular cylinder. The result matches the published unit weight tables of all major Indian TMT manufacturers to within ±1%.
Weight per metre (kg/m) = D² ÷ 162
Total length (m) = Bar length × Number of bars
Total weight (kg) = Weight per metre × Total length
Total weight (tonnes) = Total weight (kg) ÷ 1000
- D = bar diameter in millimetres (mm)
- 162 = constant derived from steel density 7850 kg/m³ and π/4 (equals 1 ÷ 0.006165)
- Bar length = length of each individual bar in metres (standard = 12 m)
- Number of bars = total quantity of bars of this diameter
Worked example: 12 mm diameter bars, 12 m length, 50 bars.
Weight per metre = 12² ÷ 162 = 144 ÷ 162 = 0.889 kg/m
Total length = 12 × 50 = 600 m
Total weight = 0.889 × 600 = 533.3 kg = 0.533 tonnes
The calculator handles this automatically — the formula is shown here for transparency.
Standard TMT Bar Weights (IS:1786)
The table below lists the theoretical unit weight for each standard TMT bar diameter as specified in IS:1786-2008. These values are calculated using the D²/162 formula and match the published weight tables of TATA Tiscon, JSW Neosteel, Vizag Steel, and SAIL. Actual bar weight may vary within the ±3% tolerance permitted by IS:1786 — weigh a sample bar at site if precise quantity verification is needed for a large purchase order.
| Diameter (mm) | Weight per Metre (kg/m) | 12 m Bar Weight (kg) | Common Use |
|---|---|---|---|
| 6 mm | 0.222 | 2.67 kg | Stirrups, ties, wire mesh |
| 8 mm | 0.395 | 4.74 kg | Slab distribution bars, ties |
| 10 mm | 0.617 | 7.40 kg | Slab main bars, small beams |
| 12 mm | 0.888 | 10.66 kg | Beam stirrups, slab reinforcement |
| 16 mm | 1.580 | 18.96 kg | Beam main bars, column ties |
| 20 mm | 2.469 | 29.63 kg | Column main bars, heavy beams |
| 25 mm | 3.858 | 46.30 kg | Heavy columns, transfer beams |
Frequently Asked Questions
Use the D²/162 formula: square the bar diameter in mm, divide by 162, and you get the weight per metre in kg. Multiply by total bar length in metres to get total weight. For a 16 mm bar that is 12 m long: (16² ÷ 162) × 12 = (256 ÷ 162) × 12 = 1.580 × 12 = 18.96 kg per bar. For 100 such bars, total weight = 18.96 × 100 = 1896 kg = 1.896 tonnes.
D²/162 is a simplified form of the density-volume formula for a solid steel cylinder. The full derivation: weight (kg/m) = π/4 × (D/1000)² × 7850 = D² × 0.006165 ≈ D²/162. The constant 7850 kg/m³ is the standard density of structural steel per IS:1786-2008. The constant 162 comes from 1 ÷ 0.006165 ≈ 162.2. This formula is universally used for TMT and MS bars in India because it is accurate to within ±1% of manufacturer-published weight tables for all standard sizes from 6 mm to 40 mm.
A 12 mm TMT bar weighs 0.888 kg per metre: 12² ÷ 162 = 144 ÷ 162 = 0.889 kg/m. A standard 12 m bar therefore weighs 10.67 kg. This matches the IS:1786 theoretical unit weight for 12 mm bars. Minor variation within ±3% is permitted under IS:1786 tolerances and is normal across manufacturers like TATA Tiscon, JSW Neosteel, and SAIL Vizag Steel — weigh a sample bar at delivery if you need to verify the actual weight for a large order.
Fe415 and Fe500 refer to yield strength — 415 N/mm² and 500 N/mm² respectively per IS:1786. Both grades have the same density (7850 kg/m³), so the D²/162 formula gives identical weights for both. Fe500 requires approximately 17% less steel by weight for the same load compared to Fe415, reducing material cost. Fe500D has a higher elongation percentage (minimum 16% vs 12%) giving better ductility for earthquake resistance. Fe500D is mandatory in seismic zones III, IV, and V under IS:13920 and is the most commonly specified grade in new residential construction across India.
Typical residential RCC construction in India uses 3.5–5 kg of TMT steel per square foot of built-up area (approximately 37–54 kg/m²). Low-rise residential buildings (ground floor plus 1 to 3 floors) average around 4 kg/sq ft. Commercial buildings and high-rises typically use 5–7 kg/sq ft due to heavier structural loads and longer spans. These are rule-of-thumb estimates for preliminary budgeting only — actual steel quantity must be determined from the structural engineer's bar bending schedule (BBS) for accurate procurement.
The D²/162 formula gives the theoretical unit weight per IS:1786, accurate to within ±1% for bars manufactured to IS standards. Real bars may vary within the ±3% weight tolerance permitted by IS:1786. For purchase orders, the calculator result is sufficiently accurate for estimating quantity and cost. For structural design verification, always use the unit weights certified on the manufacturer's IS test certificate, and weigh a sample from the delivery if you are procuring large quantities worth more than ₹5 lakh.
The standard mill length for TMT bars in India is 12 metres (approximately 40 feet). Bars are also available as cut-length pieces at 6 m for smaller sites, or in random length (RL) bundles averaging 11–13 m. IS:1786 permits supply in standard lengths of 12 m or multiples thereof. For construction site calculations, use 12 m as the default bar length unless a specific cut-length has been called out in the bar bending schedule. Ordering in standard 12 m lengths minimises wastage and is typically priced lower per tonne than cut lengths.
Divide kilograms by 1000 to get metric tonnes. For example, 533 kg ÷ 1000 = 0.533 tonnes. Steel is traded and priced per metric tonne (1000 kg) by suppliers including TATA Tiscon, JSW Neosteel, and Vizag Steel — the calculator displays both kg and tonnes so you can directly match against supplier invoices. Note that 1 metric tonne = 1000 kg exactly; do not confuse with the imperial short ton (907 kg) or the imperial long ton (1016 kg), which are not used in the Indian steel trade.