Kumar IronColumn and beam steel calculator
Estimate the kg of TMT in one column or beam from its size, main bars and stirrups, then scale to the number of members.
Formula
- Weight of a bar = length x d² / 162 kg, with d in mm and length in m.
- Main steel = number of bars x (member length + lap + hooks) x d² / 162. Lap is optional and uses your multiple of bar diameter (40d is a common value) per splice.
- Stirrup cutting length = 2(a + b) - 8 x cover + 2 x 10d, where a and b are the member width and depth in mm. The first two terms give the outside perimeter of the stirrup, and 10d is the extension of each 135 degree hook.
- Number of stirrups = member length / spacing (rounded down) + 1.
- Per member = main + stirrups, then x (1 + wastage %) x number of members.
Source and assumption: bar bending conventions follow IS 2502 and SP 34. The stirrup hook of 10d (minimum 75 mm) is the usual 135 degree detail for seismic zones under IS 13920. The +20d allowance is the common site shortcut that nets the bend deductions (2d per 90 degree bend, 3d per 135 degree bend) against hook lengths, so it can differ slightly from a full schedule. Sources vary on hook allowances, so check your drawing.
Total steel: 41.3 kg (0.041 tonnes) for 1 beam, including 5% wastage
| Item | Quantity | Kg per member |
|---|---|---|
| Main bars 16 mm | 4 x 4.00 m | 25.3 |
| Stirrups 8 mm | 27 x 1.320 m | 14.1 |
| Per member, no wastage | 39.4 | |
| Per member, +5% | 41.3 |
Estimate only. The structural drawing and bar bending schedule govern. Rounded stirrup counts, cranked bars and closer spacing at supports are not modelled.
Related
For a whole house use the steel calculator. Check bar weights in the TMT bar weight chart, and read the guide on lap length for TMT bars in slab and column.
FAQ
- How is stirrup cutting length calculated?
- Outside perimeter of the stirrup, 2(a + b) - 8 x cover, plus two 135 degree hooks at 10 x bar diameter each. For a 230 x 450 mm beam with 25 mm cover and 8 mm stirrups: 2 x 680 - 200 + 160 = 1320 mm.
- How many stirrups are there in a beam or column?
- Length divided by spacing, rounded down, plus 1. A 3 m beam at 150 mm spacing has 3000 / 150 + 1 = 21 stirrups. Real drawings use closer spacing near supports, so use the BBS for the final count.
- How do I convert bar length to kg?
- Weight per metre = d squared / 162, with d in mm. A 16 mm bar weighs 256 / 162 = 1.58 kg per metre. This matches the TMT bar weight chart.
- Should I include lap length?
- Turn it on when main bars are spliced, for example column bars lapped above each slab. The calculator uses your lap length as a multiple of bar diameter times the number of splices. Required lap depends on grade, bar size and zone, so take it from the drawing.
- Is this the same as a bar bending schedule?
- No. It is a quick estimate for one standard member. Cranked bars, extra top steel, closer stirrups at supports and different bar sizes are not modelled. The structural drawing and BBS govern.
Send us your bar list and we will quote TMT bars for your columns and beams.