How To Calculate The Weight Of A Tmt Bar - Metro Ispat

By Author: Vaibhavi
Total Articles: 6
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Why weight calculation matters
When you purchase TMT bars from a vendor like Metro Ispat, you're often dealing in tonnes of steel (e.g., “10 tons of 16 mm TMT bar”). But to order appropriately, compare quotes, estimate cost and schedule logistics, you need to know the weight of each bar or bundle. Correct calculation ensures:
Accurate budgeting: steel is heavy and expensive, so knowing weight avoids over-ordering or under-ordering.

Logistics planning: transport, handling and crane loads all depend on weight.

Structural design compliance: engineers check that the required steel weight per metre (kg/m) is delivered in the correct diameter and grade.

Vendor verification: to check that what you receive matches the specification in terms of weight.

Metro Ispat, being a manufacturer, emphasises “Precision in Manufacturing, Strength in Every Bar” (as shown on their website).
Understanding the formula: D² × L / 162
The widely accepted formula to calculate the weight of a round steel bar (such as a TMT bar) is:
Weight (W) = D² × L ÷ 162
...
... where:
D = diameter of the bar in millimetres (mm)

L = length of the bar in metres (m)

162 = a constant derived from the steel density and unit conversions.

This formula appears in multiple sources. For example, one blog states: “Here is the formula for calculating the weight of the TMT bar: W = D² L / 162.”
Also, a technical article shows the derivation of 162: using steel density (~7850 kg/m³) and converting mm to m.
Derivation made simple:
Steel has density ~ 7,850 kg/m³.
Volume of a cylinder (bar) = π × (diameter in metres)² ÷ 4 × length in metres.

Converting units and simplifying gives the approximate constant 1/162 when D is in mm and L in metres.
Example calculation
Suppose you have a TMT bar of diameter = 12 mm, length = 12 m. Using the formula:
W = (12 × 12 × 12) ÷ 162 = (1,728) ÷ 162 ≈ 10.67 kg.
This matches typical published charts (12 mm bar weighs approx. 0.888 kg per metre → so for 12 m length ~10.66 kg).
If you instead had a 16 mm diameter bar, 12 m length:
W = (16 × 16 × 12) ÷ 162 = (3,072) ÷ 162 ≈ 18.96 kg. Which aligns with charts giving ~1.58 kg/m for 16 mm.

Step-by-step procedure
Here’s a clear step-by-step method you or your procurement/engineering team can follow:
Measure or check diameter (D) – Ensure you have the correct diameter of the TMT bar (commonly 8 mm, 10 mm, 12 mm,16 mm, 20 mm, 25 mm in India).

Measure or check length (L) – Typically TMT bars come in standard lengths (for example 12 m in India).

Apply the formula: W = D² × L ÷ 162 → result gives weight in kilograms.

For multiple bars, multiply W by number of bars to get total weight.

Cross-check with manufacturer’s bundle weight chart – Most manufacturers (including Metro Ispat) provide standard bundle weights or kg/m values for each diameter. This helps verify tolerance.

Allow for tolerance – Manufacturing standards allow slight variation (±7% for example) from nominal weight per metre.
Use charts or calculators for quick reference – There are weight charts (kg/m by diameter), and even online calculators to speed up this task.

Typical weight chart & practical use
Here are typical approximate weights per metre for various diameters (based on D²/162):
8 mm → 0.395 kg/m (8×8/162 ≈ 0.395)
10 mm → 0.617 kg/m
12 mm → 0.888 kg/m
16 mm → 1.58 kg/m
25 mm → 3.86 kg/m
Practical use: If you know you need, say, 200 m of 12 mm bar, you estimate weight = 200 m × 0.888 kg/m ≈ 177.6 kg. This helps with procurement (you may round up to 180 kg or 0.18 tonnes) and transport planning.

Tips & cautions
Always confirm actual length: Some manufacturers may supply slightly shorter or longer bars (e.g., 11.8 m or 12.2 m) — adjust L accordingly.

Check grade / tolerance: Bars of the same diameter may have different weights per metre depending on grade, manufacturing method, or compliance with standard (e.g., IS 1786 in India).
Bundle weights vary: A bundle weight for a given diameter is not always simply “number of bars × weight of one bar”. Variations may occur due to length differences, cutting losses, etc. For example: for 8 mm 10 rods may weigh ~45 kg per bundle.
Be careful of unit conversions: The formula uses diameter in mm, length in metres, and gives weight in kg. If you use different units (feet, inches, mm length), convert accordingly.
Use manufacturer data: Good manufacturers (such as Metro Ispat) publish weight charts or kg/m values, so use those for final check.
Material density assumption: The standard 162 constant is based on steel density ~7850 kg/m³. If you are dealing with special alloy bars or non-standard density, adjust accordingly.

Why a serious steel supplier like Metro Ispat emphasises this
Metro Ispat highlights its focus on “Quality and Expertise … Precision in Manufacturing, Strength in Every Bar” (as seen on their site). For project planners, engineering teams and procurement departments, using accurate weight calculations means you can rely on Metro Ispat’s bars to meet the structural requirements you’ve specified. In many cases, when mismatches occur the root cause is mis-estimation of steel weight rather than failure of the material itself. By ensuring your calculations are correct, you reinforce the value that a reputable supplier provides.

Conclusion
Calculating the weight of a TMT bar is not a mysterious or overly complex task — it simply requires knowing the diameter, length, and applying the formula W = D² × L ÷ 162. Armed with that, and cross-checked with weight charts or manufacturer data (for example from Metro Ispat), you can confidently estimate the steel requirement for your construction project, verify vendor supplies and manage costs. Whether you’re ordering standard 12 m bars, planning bundles, or tallying tonnes for a multi-storey building, this calculation is an essential tool in your toolkit.
By mastering this calculation and understanding the nuances (bundle weights, tolerance, length variations, grade differences), you’ll be in a stronger position — and your project will benefit from the precision and reliability that quality suppliers like Metro Ispat deliver.