🏗️ Reinforcement Steel Calculator 2026 — IS 1786 D²/162 Formula
Your Steel Calculation (2026)
Total Weight:—
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Unit Weight (kg/m):—
Weight per Bar:—
Total Length:—
Bars per Tonne:—
Weight in Quintals:—
IS 1786 Tolerance:—
⚠️ Nominal weights per IS 1786:2008. Actual delivered weight may vary within tolerance bands. Verify with mill test certificate.
📌 Quick Answer: Rebar weight (kg/m) = D² / 162, where D is bar diameter in mm. A 12mm bar weighs 0.888 kg/m (10.66 kg per 12m bar). There are approximately 94 bars of 12mm per tonne. Standard Indian bar length is 12 metres .
ℹ️ This calculator uses the IS 1786:2008 nominal weight formula for TMT reinforcement bars. Actual weight may vary within IS tolerance bands.
📊 Formula: Weight (kg/m) = D² ÷ 162 | Total Weight = Unit Weight × Length × Number of Bars
💡 Important: Vendors often supply bars at the lower tolerance limit to reduce material cost. A 12m T16 bar at −3% weighs 18.38 kg instead of 18.96 kg nominal .
📊 IS 1786 Rebar Weight Chart (6mm to 40mm)
Bar Diameter
Weight (kg/m)
Weight per 12m Bar
Bars per Tonne
Common Use
6 mm (T6)
0.222
2.66 kg
376
Stirrups, light distribution
8 mm (T8)
0.395
4.74 kg
211
Stirrups, slab distribution
10 mm (T10)
0.617
7.40 kg
135
Slab main bars, beam stirrups
12 mm (T12)
0.888
10.66 kg
94
Slab main, beam bottom
16 mm (T16)
1.580
18.96 kg
53
Beam main, column bars
20 mm (T20)
2.469
29.63 kg
34
Beam, column, footings
25 mm (T25)
3.858
46.30 kg
22
Heavy beams, raft foundations
32 mm (T32)
6.313
75.76 kg
13
Heavy structural elements
40 mm (T40)
9.864
118.37 kg
8
Massive foundations, bridges
Values per IS 1786:2008 nominal weights. 12m standard length assumed .
🏗️ Example 1: Slab Reinforcement
Bar: 12mm T12 | Length: 12m | Quantity: 50 bars
Unit Weight: 0.888 kg/m
Weight per Bar: 10.66 kg
Total: 50 × 10.66 = 532.8 kg
🏗️ Example 2: Column Reinforcement
Bar: 20mm T20 | Length: 12m | Quantity: 20 bars
Unit Weight: 2.469 kg/m
Weight per Bar: 29.63 kg
Total: 20 × 29.63 = 592.6 kg
How the Reinforcement Steel Calculator Works
This reinforcement steel calculator 2026 uses the standard IS 1786:2008 formula to calculate TMT rebar weight. The formula is simple: Weight (kg/m) = D² / 162, where D is the nominal bar diameter in millimetres .
The constant 162 is derived from steel density (7,850 kg/m³) and the circular cross-section of the bar. It yields the familiar values: 8mm = 0.395 kg/m, 10mm = 0.617 kg/m, 12mm = 0.888 kg/m, and so on .
Why the D²/162 Formula Works
Steel has a density of approximately 7,850 kg per cubic metre. A round bar's cross-sectional area is πD²/4. Multiplying area by density and converting units gives: Weight per metre = πD²/4 × 7850 / 10⁶ ≈ D² / 162.16. Indian practice rounds to 162 for simplicity — the error is only about 0.1%, well within IS tolerance .
Standard Bar Lengths and Quantities
In India, the standard TMT bar length is 12 metres. Some manufacturers supply 11.5m or 12.2m, so always verify actual length when calculating delivery weights .
The number of bars per tonne varies dramatically by diameter. An 8mm bar requires 211 pieces to reach a tonne, while a 40mm bar needs only 8. This is why procurement planning must account for bar diameter, not just total tonnage .
IS 1786 Weight Tolerances
Nominal weights are theoretical. Actual delivered bars can deviate within IS-specified tolerances :
6mm–8mm: ±7% tolerance
10mm–12mm: ±5% tolerance
16mm–20mm: ±4% tolerance
25mm and above: ±3% tolerance
Smaller bars have larger percentage tolerances because surface deformations (ribs) contribute relatively more mass. Mills often supply at the lower tolerance limit to save material — a 12m T16 bar at −3% weighs 18.38 kg instead of 18.96 kg nominal .
Reinforcement Steel vs. Structural Steel
This calculator is for reinforcement bars (rebar) — the TMT bars embedded in concrete to carry tensile stress. Structural steel (I-beams, channels, angles) uses different weight tables based on section properties, not the D²/162 formula. If you need structural steel weights, use a steel section weight table instead.
Why Accurate Rebar Weight Matters
Rebar is typically 15–25% of a concrete structure's material cost. Overestimating by 5% on a 100-tonne project wastes 5 tonnes of steel — thousands of dollars. Underestimating causes site delays and emergency procurement at premium prices. Accurate weight calculation from the D²/162 formula, combined with IS tolerance awareness, is essential for both procurement and billing .
🏗️ Quick Reference — IS 1786 Rebar Weights
Bar
kg/m
kg per 12m
Bars/Tonne
8mm
0.395
4.74
211
10mm
0.617
7.40
135
12mm
0.888
10.66
94
16mm
1.580
18.96
53
20mm
2.469
29.63
34
25mm
3.858
46.30
22
❓ Frequently Asked Questions
What is the formula for rebar weight per metre?
The standard IS 1786 formula is Weight (kg/m) = D² / 162, where D is the bar diameter in millimetres. For example, a 12mm bar weighs 12² / 162 = 0.888 kg/m .
How much does a 12mm TMT bar weigh?
A 12mm TMT bar weighs approximately 0.888 kg per metre. A standard 12-metre bar weighs about 10.66 kg. There are roughly 94 bars of 12mm per tonne .
What is the standard length of a TMT rebar in India?
The standard bar length in India is 12 metres. Some manufacturers supply 11.5m or 12.2m lengths, so always verify actual length when calculating delivery weights .
What is the tolerance on rebar weight?
IS 1786:2008 specifies mass tolerances: ±7% for 6mm–8mm, ±5% for 10mm–12mm, ±4% for 16mm–20mm, and ±3% for 25mm and above. Actual delivered batches may run light or heavy within these bands .
How many 8mm bars are in one tonne?
An 8mm bar weighs 0.395 kg/m, so a 12m bar weighs 4.74 kg. One tonne (1000 kg) contains approximately 211 bars of 8mm at 12m length .
💡 Expert Tips for Rebar Procurement
Tip #1: Always add 3–5% wastage allowance to your calculated weight. Cutting, laps, and site losses consume more steel than the theoretical BBS shows .
Tip #2: Check the mill test certificate (MTC) for actual weight per metre. If the vendor is supplying at −5% tolerance, you're getting less steel than the nominal invoice suggests .
Tip #3: For large projects, weigh a sample of bars from each delivery. A 12m T12 bar should weigh 10.66 kg nominal — if it's consistently 10.2 kg, you're paying for steel you're not receiving .
Tip #4: Use the D²/162 formula for quick site calculations. For 16mm bars, the multiplier is 1.58 kg/m — memorize the common sizes and you can estimate weight without a calculator .
Tip #5: When comparing quotes from different suppliers, ask for weight per metre at actual delivered diameter, not just nominal. Rib height and deformation pattern affect actual mass .
🏗️ Need to Calculate Rebar Weight Right Now?
Get instant results using the IS 1786 D²/162 formula. 6mm to 40mm bars.
🛡️ CDCalculators reinforcement steel calculator 2026 — data sources: IS 1786:2008 nominal weights, steel density 7,850 kg/m³. Last updated October 24, 2026. Disclaimer: Nominal weights only. Actual delivered weight may vary within IS tolerance bands. Verify with mill test certificate for procurement.