Steel is one of the biggest costs in any RCC construction project. Ordering too little delays work, and ordering too much locks up your budget. The easiest way to avoid both is to know the weight of the TMT bars you are using.
This guide gives you a complete TMT bar weight chart, the formula behind it, and a simple example so you can estimate your requirement with confidence.
Why TMT Bar Weight Matters
TMT steel bars are sold by weight (per kg or per tonne) but used by length (in meters). To convert between the two, you need the weight per meter of each bar diameter.
Knowing it helps you to:
- Estimate the total steel needed for a slab, beam, column or foundation
- Compare quotations from different suppliers accurately
- Check that the bars delivered match the quantity you paid for
- Plan transport and site storage
TMT Bar Weight Formula
The standard formula for the weight of a steel bar per meter is:
Weight per meter (kg) = D² ÷ 162
Here, D is the diameter of the bar in millimeters.
Example: For a 12mm bar, the weight per meter = (12 × 12) ÷ 162 = 144 ÷ 162 = 0.889 kg per meter.
TMT Bar Weight Chart (8mm to 32mm)
The table below assumes the standard bar length of 12 meters.
| Diameter | Weight per Meter (kg) | Weight per 12m Bar (kg) | Approx. Bars per Tonne |
|---|---|---|---|
| 8mm tmt steel bar | 0.395 | 4.74 | 211 |
| 10mm tmt steel bar | 0.617 | 7.40 | 135 |
| 12mm tmt steel bar | 0.889 | 10.67 | 94 |
| 16mm tmt steel bar | 1.580 | 18.96 | 53 |
| 20mm tmt steel bar | 2.469 | 29.63 | 34 |
| 25mm tmt steel bar | 3.858 | 46.30 | 22 |
| 32mm tmt steel bar | 6.321 | 75.85 | 13 |
Values are rounded. Weight does not change with grade, so Fe 500D and Fe 550D bars of the same diameter have the same nominal weight.
How to Use the Chart: A Simple Example
Suppose your slab design needs a total of 1,200 meters of 10mm TMT bars.
- Weight per meter of 10mm bar = 0.617 kg
- Total weight = 1,200 × 0.617 = 740.4 kg
If the supplier quotes per tonne, you need about 0.74 tonnes. Add a 3 to 5 percent allowance for cutting waste, overlaps and bending, and order about 0.78 tonnes.
You can repeat this for each bar size in your bar bending schedule and add the results to get your total steel requirement.
Weight Tolerance Under IS 1786
No bar weighs exactly the nominal figure, and the standard allows a small variation. IS 1786 sets permissible tolerances on nominal mass, and these are tighter for thicker bars. As a rough guide, thinner bars (up to 10mm) are allowed a larger percentage tolerance than thicker bars (above 16mm). Check the latest edition of IS 1786 for the exact figures.
This matters because a bar that consistently weighs below the permitted limit has less steel in it than its diameter claims. That means less strength than your design assumed.
How to Check the Weight at Your Site
You do not need special equipment for a basic check:
- Take a few bars of the same diameter from the delivered lot.
- Cut a piece of exactly 1 meter.
- Weigh it on a calibrated scale.
- Compare it with the weight per meter in the chart above.
If the result falls well outside the tolerance, raise it with your supplier before using the material. Also ask for the Mill Test Certificate for the batch, which confirms mechanical properties and chemical composition.
Why Weight Consistency Reflects Quality
Weight consistency is a sign of controlled manufacturing. Mills that roll bars to accurate dimensions, with proper rib patterns and uniform Thermex quenching, deliver bars whose weight stays close to the standard. Poorly controlled production can lead to underweight or uneven bars, and buyers often only find out after the steel is already in the structure.
That is why builders should buy BIS-certified Fe 500D or Fe 550D TMT bars from an established manufacturer rather than choosing on price alone.
Frequently Asked Questions
A 12mm bar weighs about 0.889 kg per meter, or roughly 10.67 kg for a 12-meter bar.
About 135 bars of 12 meters each.
Yes. Weight depends on diameter and length, not on grade. The grades differ in strength, not in nominal weight.
It comes from the cross-sectional area of a round bar and the density of steel (about 7,850 kg per cubic meter). It gives weight per meter directly in kg when D is in mm.
Yes. Most builders add 3 to 5 percent for cutting, laps and bends, depending on the design.
Choose Quality TMT Bars in Indore
Accurate estimation starts with reliable material. Shivangi TMT Bars manufactures Fe 500D and Fe 550D CRS TMT bars in sizes from 8mm to 32mm, made to IS 1786 standards for residential, commercial and infrastructure projects across Indore and Madhya Pradesh.