How to Understand the Weight of TMT Rods (Simple Guide)

TMT (Thermo-Mechanically Treated) steel rods are sold by weight, not by number of rods. Understanding how TMT rod weight is calculated helps you estimate cost correctly, avoid under-ordering, and verify material at site.

This guide explains TMT rod weight in the simplest possible way, even if you’re not an engineer.

What You Need to Know First

• TMT rods are measured in kilograms (kg) or metric tons

• Standard rod length is 12 meters

• Weight depends only on the diameter of the rod

• Grade (Fe 415 / Fe 500 / Fe 550) does not change weight

  
  

Step 1: Understand the Weight Formula

The standard formula used across construction sites is:

Weight (kg)= D² / 162

Where:

• D = Diameter of the TMT rod in millimeters

• 162 = Constant based on steel density

• Length = Length of the rod in meters (usually 12 m)

Step 2: Know the Unit Weight per Meter (Quick Reference)

TMT Rod Size	Weight per Meter (kg)	Weight per 12 m Rod (kg)
8 mm	0.395	4.74
10 mm	0.617	7.40
12 mm	0.888	10.66
16 mm	1.58	18.96
20 mm	2.47	29.64
25 mm	3.86	46.32

💡 Tip: These values are industry-standard and accepted on site.

Step 3: Calculate the Weight of One TMT Rod (Example)

Example: 12 mm TMT Rod

• Diameter = 12 mm

• Length = 12 m

122162×12=10.66 kg\frac{12^2}{162} \times 12 = 10.66 \text{ kg}162122​×12=10.66 kg

So, one 12 mm TMT rod weighs ~10.66 kg.

Step 4: Calculate Total Weight for Multiple Rods

Example

• Rod size: 16 mm

• Number of rods: 50

Weight per rod = 18.96 kg

Total weight =50 × 18.96 = 948 kg (≈ 0.95 ton)

Step 5: Convert Weight into Number of Rods

This is useful when ordering steel.

Example

• Required steel: 3,000 kg

• Using: 12 mm rods

Length required =3,000 ÷ 0.888 = 3,378 m

Number of rods =3,378 ÷ 12 = 282 rods

Step 6: Why Weight Matters More Than Rod Count

• Steel is billed by weight

• Different diameters have very different weights

• Counting rods alone can lead to wrong billing

• Site engineers always verify weight + diameter

  
  

Step 7: Common Mistakes to Avoid

• Assuming all rods weigh the same

• Ignoring diameter tolerance

• Forgetting lap length and wastage (add 3–5%)

• Mixing different bar sizes while estimating

  
  

Quick Site Tip (Easy Memory Trick)

• 12 mm bar ≈ 11 kg

• 16 mm bar ≈ 19 kg

• 20 mm bar ≈ 30 kg

This shortcut helps during quick site checks.

Final Takeaway

Understanding TMT rod weight helps you:

✔ Estimate steel accurately

✔ Control construction costs

✔ Verify supplier billing

✔ Reduce material shortages and wastage

Whether you’re a homeowner or contractor, knowing this basic calculation gives you better control over your project.