Got a bundle of rods in front of you and a purchase order in your hand? Here is the quick answer on TMT bar weight per meter: a 12 mm bar weighs about 0.888 kg per meter, and an 8 mm bar about 0.395 kg per meter. Every other size follows from one simple TMT bar weight formula: weight (kg per meter) = D² ÷ 162.2, where D is the nominal diameter in millimeters.
Below you will find a full TMT bar weight chart from 6 mm to 40 mm, three worked examples of how to calculate TMT bar weight, and the reasons two charts can disagree slightly.
TMT bar weight per meter chart (6 mm to 40 mm)
This TMT bar weight chart shows theoretical values, worked out from nominal diameters with a steel density of 7850 kg/m³. The last column assumes a bar length of 12 m, which is common, but please confirm the length with your supplier.
| Bar diameter (mm) | Weight per meter (kg/m) | Weight of one 12 m bar (kg, rounded) |
|---|---|---|
| 6 | 0.222 | 2.7 |
| 8 | 0.395 | 4.7 |
| 10 | 0.617 | 7.4 |
| 12 | 0.888 | 10.7 |
| 16 | 1.578 | 18.9 |
| 20 | 2.466 | 29.6 |
| 22 | 2.984 | 35.8 |
| 25 | 3.853 | 46.2 |
| 28 | 4.834 | 58.0 |
| 32 | 6.313 | 75.8 |
| 36 | 7.990 | 95.9 |
| 40 | 9.865 | 118.4 |
All values are rounded. If another chart shows a number that is a hair different, that is normal, and the section on why charts differ explains it.
What is the TMT bar weight formula?
TMT stands for thermo-mechanically treated, a type of ribbed steel bar used to reinforce concrete (often called rebar). Its weight is usually quoted as unit weight, meaning kilograms per meter (kg/m). The TMT bar weight formula, in its common shortcut form, is:
Weight (kg per meter) = D² ÷ 162.2
Here D is the nominal bar diameter in millimeters. Square it, divide by 162.2, and you have the weight of one meter of bar.
Where does 162.2 come from? It is not a magic number. A round bar is a cylinder of steel, so its weight per meter is its cross-sectional area multiplied by the density of steel. With the usual density of 7850 kg/m³ and the diameter in millimeters, the arithmetic works out to about 0.006165 × D² kg per meter. Divide 1 by 0.006165 and you land on roughly 162.2.
If you prefer the long form, it is this:
Weight per meter (kg) = (π ÷ 4) × D² × 7850, with D in meters
To get the weight of a whole bar, multiply the weight per meter by its length in meters. Our own Rebar & TMT Bar Weight Calculator uses the long form behind the scenes.
How to calculate TMT bar weight: three worked examples
Once you know the formula, learning how to calculate TMT bar weight takes about a minute. Here are three situations you are likely to meet on a job.
1. Sanity-checking a delivery. You ordered 50 bars of 12 mm, each 12 m long.
- One bar: 0.888 kg/m × 12 m ≈ 10.65 kg
- Fifty bars: 10.65 kg × 50 ≈ 533 kg
On paper, the order should weigh about 533 kg. Real bars never match the paper figure exactly, so treat this as a quick sanity check, not a verdict.
2. Weight of a cut length. You need 100 m of 10 mm bar.
- 0.617 kg/m × 100 m ≈ 61.7 kg
3. Working backwards from weight. You have 100 kg of 8 mm bar and want to know the length.
- 100 kg ÷ 0.395 kg/m ≈ 253 m
Why do TMT bar weight charts show different numbers?
Put three TMT weight charts side by side and you will often find small mismatches. Nobody is necessarily wrong. These are the usual reasons:
- Different constants. Some charts use D² ÷ 162, others D² ÷ 162.2. The two differ by about 0.12%, which is roughly 1.2 kg on every tonne.
- Rounding. One chart rounds to two decimals, another to three. Multiply by a few hundred meters and the gap becomes visible.
- Different density. Weight is directly proportional to density, so a chart built on a different density value shifts every number by the same percentage.
- Real bars are not perfect cylinders. TMT bars have ribs, and the actual diameter can vary slightly from bar to bar. The standard allows a tolerance on mass, so a real bar rarely weighs exactly what the chart says.
The Bureau of Indian Standards (BIS) publishes IS 1786:2008, the Indian Standard for high strength deformed steel bars and wires for concrete reinforcement, along with a product manual that explains how bars are sampled and tested for certification, including checks on mass and mass tolerance. For exact tolerance limits, please refer to the current standard from BIS.
How to use the chart on a real job
Four habits keep the numbers useful:
- Use the nominal diameter. A 12 mm bar goes into the chart as 12, even if your calipers read a little different.
- Grade does not enter the formula. The calculation uses only diameter and density, so Fe 415, Fe 500, Fe 500D and Fe 550 bars of the same nominal size share the same theoretical weight.
- Confirm the bar length. Twelve meters is common, but your order may say something else.
- Treat the chart as a cross-check. If a delivery looks off, look at your purchase terms and the supplier's test certificate as well, not the chart alone.
How we calculated these numbers
Every weight on this page comes straight from the formula above: (π ÷ 4) × D² × 7850, using nominal diameters. We worked each value out directly rather than copying it from another chart, then rounded for display. Weights per meter are shown to three decimals and 12 m bar weights to one decimal.
The 12 m bar column is simply the weight per meter multiplied by 12. Prices are left out on purpose, because they change often and depend on your supplier.
Skip the math: use our free TMT bar weight calculator
If you would rather not square numbers on site, try our free Rebar & TMT Bar Weight Calculator. Pick a diameter, enter the length, and it does the rest in your browser. Working with a plain round bar instead? The Round Bar Weight Calculator is the one to use.
More guides from the same series:
- Checkered Plate Weight per Square Meter: why every chart gives a different number
- Gauge vs Thickness: why the same gauge number is not the same size
- All BytePriva calculators
TMT bar weight FAQ
What is the 12 mm TMT bar weight per meter?
About 0.888 kg per meter, based on a nominal diameter and a steel density of 7850 kg/m³. A 12 m bar of that size comes to roughly 10.65 kg.
What is the 8 mm TMT bar weight per meter?
About 0.395 kg per meter, so a 12 m bar weighs roughly 4.7 kg.
What is the 10 mm TMT bar weight per meter?
About 0.617 kg per meter, so a 12 m bar weighs roughly 7.4 kg.
What is the 16 mm TMT bar weight per meter?
About 1.578 kg per meter, so a 12 m bar weighs roughly 18.9 kg.
What does TMT stand for?
Thermo-mechanically treated. It describes how the steel bar is processed during manufacturing.
Is the formula D² ÷ 162 or D² ÷ 162.2?
Both are shortcuts for the same calculation. The 162.2 version follows directly from a steel density of 7850 kg/m³, and the two differ by only about 0.12%.
Does the steel grade change the weight per meter?
Not in the calculation. It depends only on the nominal diameter and the density, so bars of the same nominal size in different grades share the same theoretical weight.
Why does the delivered weight not match the chart exactly?
Charts show theoretical weight. Real bars have ribs, small variations in diameter and a permitted mass tolerance, and charts also round their numbers. For billing questions, check your purchase terms and the supplier's test certificate.
Disclaimer
The weights in this article are theoretical values calculated from nominal diameters and a steel density of 7850 kg/m³. They are shared for general information and quick planning only. Actual bars vary because of rolling tolerances, rib pattern, real dimensions and the manufacturer's process.
Please do not use this article as the only basis for structural design, material billing disputes or any safety-critical decision. For those, rely on the current Indian Standard, the manufacturer's test certificate and a licensed structural engineer. Standards, product ranges and supplier practices can change over time, so check the current details yourself before acting. Use of this information is at your own risk. See our full Disclaimer for details.
Written by the BytePriva Team. Last reviewed: 22 October 2026.