Kumar IronUpdated
In this guide
Size, weight and typical use
Weight per metre follows the D²/162 formula, where D is the bar diameter in mm. A standard bar is 12 m long. The uses below are typical for a G+1 house. Your engineer's drawing decides the final sizes.
| Diameter | Weight per metre | Weight of a 12 m bar | Typical use |
|---|---|---|---|
| 6 mm | 0.222 kg | 2.66 kg | Light stirrups, ties, small lintels |
| 8 mm | 0.395 kg | 4.74 kg | Stirrups, slab distribution bars, chajja |
| 10 mm | 0.617 kg | 7.40 kg | Slab main bars, stirrups, small beams |
| 12 mm | 0.888 kg | 10.66 kg | Slab and beam bars, lintels, staircase |
| 16 mm | 1.578 kg | 18.94 kg | Beam main bars, columns |
| 20 mm | 2.466 kg | 29.59 kg | Columns, long span beams, footings |
| 25 mm | 3.853 kg | 46.24 kg | Heavy columns and footings, larger buildings |
Use the TMT bar weight chart or the steel calculator to turn lengths into kilograms.
How the sizes split in a house
Do not swap one size for another to save money without asking the engineer. Two 10 mm bars are not equal to one 16 mm bar, and fewer, thicker bars are not a like for like change.
- Footings and columns: 12, 16 and 20 mm bars carry the vertical load down to the ground.
- Beams: 12 to 20 mm bars at the top and bottom, with 8 mm stirrups holding them in shape and resisting shear.
- Roof slab: 8 or 10 mm bars in both directions, closely spaced.
- Stirrups and ties: 6 or 8 mm, bent into rectangles around the main bars. They look minor but they are what keeps a column from bursting sideways.
How to order the mix
Ask your engineer or contractor for a bar bending schedule. It lists each bar size with total length. Convert each total to kilograms using the weight per metre, add 5 to 8 percent for laps and cutting waste, and order in the same split.
A rough planning split for a small house is about half the steel in 10 and 12 mm, a third in 16 mm and above, and the rest in 8 mm. Treat this only as a check, never as a replacement for the schedule.
Do not mix grades without checking
Buy one grade and brand across the job where possible. If the drawing calls for Fe500D, do not accept Fe500 on some sizes. Our Fe500 vs Fe500D vs Fe550D guide explains the difference, and the mill test certificate guide shows how to check what you received.
Frequently asked questions
- Which TMT bar size is used for slabs?
- Most house slabs use 8 or 10 mm bars, with 10 or 12 mm in longer spans. The drawing gives the exact size and spacing.
- Can I use 8 mm bars instead of 10 mm?
- Not unless the engineer approves it. A thinner bar carries less load, so the spacing would need to change, not just the size.
- How many 12 mm bars make a tonne?
- About 94 bars of 12 m length, since each weighs about 10.66 kg.
- Do you stock all these sizes?
- We stock TMT bars from 5 to 32 mm in several grades and brands. WhatsApp us the sizes and quantities for a quote.