Instantly calculate the weight, total tonnage, and cost of TMT steel bars for construction projects using standard engineering formulas.
6 mm
8 mm
10 mm
12 mm
16 mm
20 mm
25 mm
32 mm
40 mm
Select standard TMT bar size used in construction.
Standard factory length is usually 12 meters.
Please enter a valid length greater than 0.
Total number of rods/bars required.
Quantity must be at least 1.
Enter current market rate per kg to estimate cost.
Total Steel Weight
106.67 kg
Based on D²/162 formula
Unit Weight (kg/m):0.89 kg/m
Weight per Bar:10.67 kg
Total Tonnage:0.11 MT
Estimated Cost:6,933.33
Weight Comparison: Selected vs. Adjacent Sizes
Comparing weight of 100 bars (12m length) across different diameters.
Standard TMT Bar Weight Chart
Diameter (mm)
Weight per Meter (kg/m)
Weight per 12m Bar (kg)
Standard theoretical weights based on IS:1786 density standards.
What is TMT Steel Weight Calculation?
TMT steel weight calculation is a critical process in civil engineering, construction estimation, and site management. It involves determining the theoretical mass of Thermo-Mechanically Treated (TMT) reinforcement bars before they are procured or used. Because steel is sold by weight (metric tons or kilograms) but used by length (meters or feet) in structural drawings, accurate conversion is essential for budget control and structural integrity.
Construction managers, civil engineers, and contractors use tmt steel weight calculation to reconcile the quantity ordered with the quantity delivered. Understanding the unit weight of steel helps prevent billing discrepancies and ensures that the structural design requirements are met without excessive wastage.
Note: While physical weighing is the most accurate method, the theoretical calculation is the industry standard for estimation, billing verification, and transport logistics.
TMT Steel Weight Calculation Formula and Explanation
The universal formula used for calculating the weight of circular steel bars is derived from the density of steel. The standard density of steel is approximately 7850 kg/m³.
The simplified engineering formula used on-site is:
W = (D² / 162) × L
Where:
W = Total Weight in Kilograms (kg)
D = Diameter of the bar in millimeters (mm)
L = Length of the bar in meters (m)
162 = A derived constant (162.2 approximated) based on steel density.
Variables Reference Table
Variable
Meaning
Unit
Typical Range
D
Diameter
Millimeters (mm)
6mm – 40mm
L
Length
Meters (m)
12m (Standard)
Density
Material Density
kg/m³
7850
Key variables used in tmt steel weight calculation.
Practical Examples of TMT Steel Weight Calculation
Example 1: Residential Column Reinforcement
A contractor needs to verify the weight of 50 pieces of 16mm TMT bars, each 12 meters long.
Diameter (D): 16 mm
Length (L): 12 m
Quantity: 50 bars
Step 1: Calculate Unit Weight
Weight per meter = 16² / 162 = 256 / 162 = 1.58 kg/m
Step 2: Calculate Total Length
Total Length = 50 bars × 12 m = 600 meters
Step 3: Calculate Total Weight
Total Weight = 1.58 kg/m × 600 m = 948 kg (approx 0.95 Tonnes)
Example 2: Slab Estimation
For a roof slab, an engineer estimates the need for 8mm bars. The total running length required is 2000 meters.
Formula: (8² / 162) × 2000
Calculation: (64 / 162) × 2000 = 0.395 × 2000
Result:790 kg
How to Use This TMT Steel Weight Calculator
Follow these simple steps to get an accurate estimation for your project:
Select Diameter: Choose the diameter of the steel bar from the dropdown menu (e.g., 12mm, 16mm). These are standard sizes available in the market.
Enter Length: Input the length of a single bar. The factory standard is usually 12 meters, but you can adjust this if you have cut pieces.
Enter Quantity: Input the total number of bars or bundles you possess or intend to purchase.
Price (Optional): If you want a cost estimate, enter the current market price per kilogram.
Review Results: The tool will instantly display the unit weight, total weight in kg/tonnes, and estimated cost.
Use the "Copy Results" button to save the data for your purchase orders or site records.
Key Factors That Affect TMT Steel Weight Results
While the theoretical formula is useful, real-world weights can vary due to several factors:
1. Rolling Margin
Manufacturing standards (like IS:1786) allow for a small deviation in weight, known as the rolling margin. A 12mm bar might theoretically weigh 0.888 kg/m, but the actual weight could vary by ±3% to ±5%. Suppliers often charge based on actual weight, not theoretical.
2. Corrosion and Rust
Old or stored steel may develop rust. While light rust does not significantly affect weight, heavy scaling can reduce the effective diameter, altering the steel bar weight formula reliability.
3. Length Tolerances
Although 12m is the standard, bars may sometimes be slightly longer or shorter (e.g., 11.95m or 12.05m). Over a large quantity (e.g., 1000 bars), this small difference adds up significantly in the final tmt steel weight calculation.
4. Steel Grade and Density
Different grades of steel (Fe 415, Fe 500, Fe 550) generally have the same density (7850 kg/m³). However, alloy differences can cause microscopic variations, though negligible for general construction estimation.
5. Rib Design
TMT bars have ribs and lugs for better concrete bonding. The prominence of these ribs can slightly influence the actual weight per meter compared to a smooth bar.
6. Measurement Errors
Manual errors in counting bundles or measuring cut lengths on-site often lead to discrepancies between the calculated weight and the billed weight.
Frequently Asked Questions (FAQ)
1. Why is the constant 162 used in the formula?
The constant 162 is derived from the density of steel (7850 kg/m³). Mathematically: 0.00785 × (π × D² / 4) simplifies to D² / 162.2. For simplicity in site calculations, 162 is the accepted standard.
2. Does this calculator work for square bars?
No, this tmt steel weight calculation tool is specifically for circular TMT bars. Square bars use a different formula based on cross-sectional area (Side² × Density).
3. What is the standard length of a TMT bar?
In most countries, TMT bars are manufactured and transported in standard lengths of 12 meters (approx. 40 feet) to fit on trucks.
4. How do I convert the result to Metric Tons?
Divide the total kilograms by 1000. For example, if the result is 2500 kg, it equals 2.5 Metric Tons. Our calculator displays this automatically.
5. Is actual weight different from theoretical weight?
Yes. Actual weight is determined by weighing the truck at a weighbridge. Theoretical weight is calculated mathematically. The difference should usually be within ±3% to ±5% per standard codes.
6. Can I calculate the weight of a bundle?
Yes. Simply enter the number of bars in a bundle (usually 8-10 for thicker bars, more for thinner ones) into the "Quantity" field to get the bundle weight.
7. Does the price per kg include tax?
The input field in this calculator is a raw multiplier. If you want to include GST or VAT, ensure your "Price per Kg" input includes the tax component.
8. What is the unit weight of 12mm steel?
The unit weight of a 12mm bar is approximately 0.888 kg/m. For a full 12m bar, it is roughly 10.66 kg.
Related Tools and Internal Resources
Enhance your construction estimation with our other dedicated tools: