What is the formula for TMT bar weight?

Weight per metre (kg/m) = D² ÷ 162, where D is the bar diameter in mm. Multiply by the total length to get total weight.

What diameter TMT bars are commonly used in homes?

8mm and 10mm bars are common for slabs and lintels, while 12mm, 16mm and 20mm bars are used for beams, columns and footings depending on structural load.

How many bars are there in one bundle/tonne?

This depends on the diameter — e.g. a 12mm bar weighs about 0.888 kg/m, so a standard 12m bar weighs ~10.7 kg, meaning roughly 93 bars make up 1 tonne.

TMT Steel Bar Weight Calculator — kg & Cost Estimator

Understanding TMT Bar Weight Calculations

TMT (Thermo-Mechanically Treated) bars are the standard steel reinforcement used in RCC construction across India, valued for their high strength, ductility and weldability. TMT bars are bought and sold by weight (kg or tonnes), but used and cut by length (metres) on site — so converting between the two accurately is essential for both procurement and billing. This calculator computes the total weight of TMT bars based on diameter, length and quantity, helping you cross-check supplier invoices and plan your steel budget.

How the TMT Steel Calculator Works

The calculator uses the standard formula for steel bar weight per metre: Weight (kg/m) = D² ÷ 162, where D is the bar diameter in millimetres. This formula is derived from the density of steel (7850 kg/m³) and the circular cross-sectional area of the bar. For example, a 12mm bar weighs approximately 0.888 kg per metre (12² ÷ 162 = 0.888), while a 16mm bar weighs about 1.58 kg/m. The calculator multiplies this per-metre weight by the number of bars and the length per bar to get the total weight, then adds your selected cutting wastage percentage (typically 3-8%) to account for offcuts during bending and lapping.

Common TMT Bar Diameters and Their Uses

Diameter	Weight (kg/m)	Typical Use
8mm	0.395	Stirrups, lintels, distribution bars in slabs
10mm	0.617	Slab main bars, small beams
12mm	0.888	Slabs, beam stirrups, light columns
16mm	1.58	Beams, columns
20mm	2.47	Columns, footings, heavy beams
25mm	3.85	Heavy columns, footings, raft foundations

Understanding Steel Grades: Fe415, Fe500, Fe550

Fe415 — yield strength of 415 N/mm², traditionally used in residential construction; more ductile, performs well in seismic zones.
Fe500 — yield strength of 500 N/mm², the most widely used grade today; allows slightly less steel for the same strength compared to Fe415, often making it more economical overall.
Fe550 — yield strength of 550 N/mm², used in specialised heavy structural applications where higher strength-to-weight ratio is critical.

How to Use This Calculator

Select the bar diameter in millimetres.
Select the steel grade.
Enter the number of bars required.
Enter the length per bar (standard TMT bars are typically sold in 12m lengths).
Optionally enter the rate per kg for a cost estimate.
Select the cutting wastage percentage.
Click Calculate to see total weight, kg/metre, total length and estimated cost.

Tips for Ordering and Quality Checks

Always check for the ISI mark (IS 1786) and the manufacturer's batch certificate — this ensures the bars meet specified yield strength and ductility standards.
Plan bar cutting lists against standard 12m lengths to minimise wastage — a good bar bending schedule (BBS) can reduce wastage to under 3%.
Cross-check delivered weight against your calculated weight using the D²/162 formula — significant discrepancies may indicate diameter or length issues.
Store bars on raised supports, segregated by diameter and grade, to avoid mix-ups during placement.
For large projects (over 5-10 tonnes), negotiate directly with authorised dealers or manufacturers for better rates than retail.

Find TMT Steel Prices

Steel prices fluctuate with market conditions, so check today's TMT bar prices and find verified steel suppliers in your city through BuildHQ before placing your order.

🔩 TMT Steel Calculator

TMT Bar Weight & Quantity Calculator