Steel rebar calculator
Weight, whole bars to order and cost, from a bar schedule or from a slab's bar spacing. Unit weights are computed from the section and the density of steel, not from the d²/162 shortcut.
What are you taking off
258.73 kgRs 27,166 at Rs 105/kg · 29 bars of 12 m to order
The order
| Total weight | 258.73 kg |
|---|---|
| In tonnes | 0.259 t |
| Running length | 314.4 m |
| Whole 12 m bars | 29 |
| Cost at your rate | Rs 27,166 |
| Steel per m² of slab | — |
Unit weights, kg per metre
| Bar | Exact | d²/162 |
|---|---|---|
| 6 mm | 0.222 | 0.222 |
| 8 mm | 0.395 | 0.395 |
| 10 mm | 0.617 | 0.617 |
| 12 mm | 0.888 | 0.889 |
| 16 mm | 1.578 | 1.580 |
| 20 mm | 2.466 | 2.469 |
| 25 mm | 3.853 | 3.858 |
| 32 mm | 6.313 | 6.321 |
| Diameter | Bars | Length each | Running m | Weight | 12 m bars |
|---|---|---|---|---|---|
| 8 mm | 40 | 3.6 m | 144.0 m | 58.52 kg | 13 |
| 12 mm | 24 | 4.5 m | 108.0 m | 98.76 kg | 10 |
| 16 mm | 12 | 5.2 m | 62.4 m | 101.44 kg | 6 |
A take-off, not a bar bending schedule. Cut lengths here are what you enter or what the slab geometry gives. Bends, cranks, laps, chairs and development length are design decisions that belong to the structural drawing, and they add steel — commonly several percent beyond the wastage allowance.
Weights are nominal. IS 1786 permits the delivered bar to vary from nominal by ±7% up to 10 mm and ±5% at 12 mm and above, and mills do not cut exactly 12 m, so the weighbridge will not match this to the kilo. The whole trade estimates on nominal weight; so does this page.
Where d²/162 comes from, and what it costs you
Every site in Nepal sizes steel with the same rule of thumb: weight in kilograms per metre is the diameter in millimetres squared, divided by 162. It is not a rule at all. It is the section area times the density of steel, rounded:
- Sectionπ/4 × (d ÷ 1000)² square metres
- Density7,850 kg per cubic metre
- Togetherd² × 0.00616537, which is d² ÷ 162.196
Dividing by 162 instead of 162.196 makes every answer about 0.12% light. On one bar that is nothing. On a 12,000 kg house it is about 15 kg — still small against the ±5% mill tolerance, which is exactly why the shortcut has survived. This page computes the exact figure and prints the rule of thumb beside it, so a supplier quoting from the shortcut and an engineer quoting from the section can see they agree.
Bars are sold whole
A supplier sells a 12 metre bar. If your schedule needs 7.4 metres of 16 mm, you buy a whole bar and cut it. The order figure above counts whole stock lengths from the running length including wastage, because rounding a take-off down is how a slab stops halfway through a pour.
It does not attempt to optimise how cut lengths nest inside stock lengths. That is a cutting-list problem, it depends on what the bender is willing to splice, and a calculator that pretends to solve it will be wrong on site.
The +1 that every hand take-off drops
Bars in a slab sit at both faces of the span, so the count is the clear span divided by the spacing plus one. Over a 4 metre span at 150 mm centres that is 27 bars, not 26 — about 4% of the steel in that direction, and it always errs short.
The slab mode also deducts the clear cover from both ends of the cutting length, and adds a hook allowance if you ask for one. What it does not do is decide which direction carries the load; it assumes the main bars run the shorter way, which is the ordinary case for a one-way slab and needs checking against the drawing for anything else.
Steel per square metre, as a sanity check
The slab mode prints kilograms of steel per square metre of slab. A single-layer domestic slab usually lands somewhere near 6 to 10. If your figure is far outside that, the spacing or the diameter is probably a typo — it is a cheap check and it catches the errors that matter before the order goes in.
Working out the concrete as well?
The concrete and brick estimator covers the cement, sand, aggregate and bricks for the same structure, and the unit converter handles the mixed feet-and-metres drawings that Nepali sites actually work from. If this is the part of engineering you enjoy, civil engineering at ICE is built around it. The same take-off done by hand, wastage allowances and all, is written up in concrete and brick quantity take-off.
Common questions
- Is this Steel rebar calculator page free to use?
- Yes. Every Kaamko tool is free, with no sign-up, no account and no usage limit. They are published by Imperial College of Engineering, a Tribhuvan University-affiliated engineering college in Tathali, Bhaktapur, and are not funded by advertising.
- Does what I type get sent anywhere?
- No. This tool runs entirely in your browser: the calculation happens on your own device, nothing you type is uploaded, and nothing is stored after you close the page.
- Where do the figures come from?
- Each tool names its source on the page, along with the date that source was read. Where a rate or a slab is provisional — announced in a budget speech but not yet gazetted, for instance — the page says so rather than presenting it as settled.
- Who maintains these tools?
- Imperial College of Engineering, formerly Janakpur Engineering College, in Tathali, Bhaktapur, Nepal. Corrections are welcome by phone on 01-5091616 or through the contact page, and a figure reported as wrong is checked against its published source rather than adjusted on request.
Last checked by Imperial College of Engineering. Rates, slabs and formulas are re-checked against their published source on this date.