Reinforcement calculator
Steel / saria weight calculator
Convert a rebar schedule into kilograms and tonnes using diameter, bar count, length and an editable waste allowance.
Calculation results
How steel weight is calculated
The tool estimates the mass of round steel bar from nominal diameter and length. It does not decide how much reinforcement a structure needs.
Unit weight (kg/m) = (diameter in mm)² ÷ 162
Total length in metres = number of bars × length of each bar in metres
Weight with allowance = unit weight × total length × (1 + waste percentage ÷ 100)
Rolling tolerances, couplers, binding wire, laps, hooks and fabrication losses can affect procurement. Compare the estimate with the structural bar-bending schedule.
Worked example
Twenty 12 mm bars, each 40 ft long, equal 243.84 metres. At 0.889 kg/m, they weigh about 216.75 kg before waste and 227.58 kg (0.228 tonnes) after the default 5% allowance.
Quick nominal rebar-weight reference
| Nominal diameter | kg per metre | kg per 12 m bar | kg per 40 ft bar |
|---|---|---|---|
| 8 mm | 0.395 | 4.74 | 4.82 |
| 10 mm | 0.617 | 7.41 | 7.53 |
| 12 mm | 0.889 | 10.67 | 10.84 |
| 16 mm | 1.580 | 18.96 | 19.27 |
| 20 mm | 2.469 | 29.63 | 30.10 |
| 25 mm | 3.858 | 46.30 | 47.04 |
These are rounded theoretical weights, not a supplier's accepted delivery weights. Forty feet equals 12.192 metres, so the last two columns intentionally differ. Keep full precision when calculating a batch; rounding each metre first can shift the total.
From drawing to a checkable steel take-off
Calculate one bar mark at a time. Record the member, diameter, shape, cut length and count before multiplying by unit mass. This makes omissions visible and prevents a single total from hiding whether laps, hooks or starters were included.
The length field means the length of each bar, not the group's total length. If your schedule already says 240 m of 12 mm reinforcement, either enter the actual count and cut length or calculate 240 m as one aggregate length with no additional count multiplier. Keep the schedule reference beside the exported result so the chosen method is clear.
| Field | Check |
|---|---|
| Bar mark and member | Matches the current structural drawing and bar-bending schedule. |
| Diameter | Nominal millimetres are entered correctly for every group. |
| Cut length | Includes the bends, hooks, laps and anchorage required by the schedule, counted once. |
| Count | Matches the scheduled quantity for that mark and member count. |
| Other quantities | Chairs, binding wire, couplers and fabrication loss remain identifiable. |
The d²/162 shortcut follows from the cross-sectional area of a round bar and an assumed steel density, with unit conversion and rounding. It is a mass conversion, not proof that the delivered steel meets the specified grade, rib geometry or mechanical properties.
Interpret the allowance as extra mass
Adding 5% increases the calculated mass by 5%; it does not add specific bends, lap lengths or an exact number of purchasable stock bars. Those depend on the approved schedule and cutting plan. Use separate calculations for different diameters or cut lengths and sum their weights. A single average diameter cannot represent a mixed schedule.
Frequently asked questions
What formula is used for rebar weight?
The calculator uses diameter squared divided by 162 to estimate kilograms per metre for round steel bar, then multiplies by total length and waste.
Does this calculator design reinforcement?
No. It only converts a known diameter, count and length into weight. Bar size, spacing, laps and anchorage must come from structural drawings.
Can I enter feet instead of metres?
Yes. Select feet and the calculator converts each bar length to metres before applying the weight formula.
Sources and verification
- ISO 6935-2:2019 — Ribbed bars for concrete reinforcementInternational technical requirements for ribbed reinforcing bars; project specifications may require a different adopted standard.
- Pakistan Standards and Quality Control Authority — Civil standards catalogueOfficial catalogue covering civil materials, including cement and reinforcement standards.
- Pakistan Engineering Council — Building Code of Pakistan 2021National building-code context for safety, administration, structural work and the authority having jurisdiction.
Sources establish the technical context. Calculator planning assumptions remain separately labelled and should be checked for the specific project.
For concrete ingredients around reinforcement, use the concrete and cement calculator.