TMT Bar Weight Calculator Guide: Formula, Chart and Examples

TMT Bar Weight Calculator Guide: Formula, Chart and Examples

Steel is sold by the tonne, but it is delivered as bars. You order 2 tonnes. The truck brings a stack of 12 metre bars. How many bars should be there? How much does each one weigh? And how do you know you are not being short-changed?

You do not need a fancy app to answer these questions. You need one formula and a small chart. This guide is a simple TMT bar weight calculator in words. It covers the formula, a full weight chart from 6 mm to 40 mm, and worked examples you can copy.

How Do You Calculate TMT Bar Weight?

The TMT bar weight per metre is the bar diameter squared, divided by 162. The diameter is in millimetres, and the answer is in kilograms per metre.

The steel bar weight formula is:

Weight per metre (kg) = D x D / 162

For a 16 mm bar: 16 x 16 = 256. Divide by 162 and you get about 1.58 kg per metre.

To find the weight of a full job, use these steps:

1. Find the weight per metre with the formula, or read it from the chart below.
2. Multiply by the length of one bar, in metres.
3. Multiply by the number of bars.

The number 162 comes from the density of steel, which is about 7,850 kg per cubic metre. Some charts use 162.2, which changes the answer by only about 0.1%. (Formula source: Kenza TMT, How to Calculate Steel for Beams, Columns, Slabs and Foundations.)

What Is the TMT Bar Weight Chart for 6 mm to 40 mm?

Here is the TMT bar weight chart for all common sizes. It shows weight per metre, weight of one 12 metre bar, and the number of bars in one tonne.

(Chart check: Infralens, Rebar Weight Chart as per IS 1786.)

Different sellers round these numbers slightly. For example, 12 mm may appear as 0.888 or 0.889 kg per metre. These small gaps do not matter for planning. 

How Do You Use the Formula in Real Examples?

You can solve most site questions with one of four simple calculations. Here they are with real numbers.

Example 1: Weight of one bar. One 12 mm bar, 12 m long. The weight per metre is 12 x 12 / 162 = 0.889 kg. So one bar weighs 0.889 x 12 = about 10.67 kg.

Example 2: Weight from total length. Your drawing needs 1,200 m of 10 mm bars. Weight per metre is 0.617 kg. So the total is 1,200 x 0.617 = about 740 kg.

Example 3: Number of bars from weight. You want 950 kg of 12 mm bars. One 12 m bar weighs 10.67 kg. So 950 / 10.67 = about 89 bars.

Example 4: Metres from a tonne. How much length is in 1 tonne of 8 mm bar? 1,000 / 0.395 = about 2,531 metres, or about 211 bars of 12 m.

Once you know the total kilograms, the cost is simple. For example, 2 tonnes at an example rate of Rs 60 a kilogram is 2,000 x 60 = Rs 1,20,000.

To plan the total steel for a whole house, see how to calculate steel requirement for a house step by step.

Why Does Real TMT Bar Weight Differ From the Formula?

Real bars never weigh exactly the same as the formula. IS 1786 allows a small tolerance on weight, and it is wider for thin bars than for thick ones.

The formula gives the nominal, or ideal, weight. Mills roll bars with ribs, and small differences in diameter change the weight. The batch tolerance under IS 1786 is about plus or minus 7% for bars up to 10 mm, plus or minus 5% for bars over 10 mm and up to 16 mm, and plus or minus 3% for bars over 16 mm. 

Here is what that means for a 12 mm bar of 12 m. The ideal weight is 10.67 kg. With a 5% tolerance, an acceptable bar weighs about 10.1 to 11.2 kg. A bar well below 10.1 kg is thinner than it claims.

This is why you should weigh a sample at delivery. Our guide on how to check TMT steel bar quality shows the full set of site checks.

Should You Buy TMT Bars by Weight or by Number of Bars?

Steel is normally billed by weight, so check the weight, not only the count. A bundle with the right number of bars can still be short on weight if the bars are thin.

Ask for the weighbridge slip, or weigh a few bundles. Compare the rate per tonne from each supplier, and ask whether the rate includes transport and unloading. Also check the bar length. Bars are usually 12 m, and some suppliers use 40 ft rods, which are about 12.19 m, or about 1.6% longer. Other lengths are possible only if agreed in advance.

What Mistakes Should You Avoid When Calculating TMT Bar Weight?

Do not use the weight of one size for another size. A 16 mm bar is much heavier than a 12 mm bar, so an error here is large.

Do not forget lap length and cutting waste. Bars overlap at joints, and offcuts are lost. Add a small allowance, and ask your engineer for the right figure.

Do not mix 12 m bars and 40 ft rods in one count. Count the actual length of each bar.

Do not skip the tolerance. A few percent either way is normal, but a large shortfall is a warning sign.

Do not rely only on thumb rules for the final order. Use your engineer's bar bending schedule, and use this formula to check it.

Do not forget that skilled work counts too. You can find reinforcement work services on URSBID for cutting, bending, and fixing the bars.

Where Can You Buy TMT Steel Bars Online?

You can buy TMT steel bars online through URSBID by posting your requirement and getting quotes from verified suppliers.

Once you know the weight you need for each bar size, the next step is to compare rates. To Buy TMT Steel Bars Online through URSBID, share the grade, bar sizes, total weight, and delivery place. Registered vendors will send their quotations directly to you. Compare the rate per tonne, the delivery cost, and the test certificates before you decide.

Frequently Asked Questions

What is the formula for TMT bar weight?

Weight per metre in kg equals D squared divided by 162, where D is the bar diameter in millimetres. For a 16 mm bar, it is 16 x 16 / 162, or about 1.58 kg per metre.

How much does a 12 mm TMT bar weigh?

A 12 mm bar weighs about 0.889 kg per metre. A full 12 m bar weighs about 10.67 kg.

How many TMT bars are there in one tonne?

It depends on the size. For 12 m bars, about 211 bars of 8 mm, 94 bars of 12 mm, 53 bars of 16 mm, or 34 bars of 20 mm make one tonne.

Why does the weight of my delivered bars not match the chart?

The chart shows ideal weights. IS 1786 allows a tolerance of about 7%, 5% or 3%, depending on the bar size. A large shortfall beyond that means the bars are underweight.

How do I find the number of bars from the total weight?

Divide the total weight by the weight of one bar. For example, 950 kg of 12 mm bars divided by 10.67 kg per bar gives about 89 bars.

Final Thoughts

You do not need a special calculator to work out TMT bar weight. You need the D squared by 162 formula and the chart above. Use them to turn kilograms into bars, to plan your order, and to check what arrives. A weight check at delivery protects you from thin bars. A few minutes of arithmetic can save you thousands of rupees.

Ready to compare prices? Get TMT steel bar rates on URSBID by posting your requirement, and receive quotes from verified suppliers.