Input details
Pick a profile, enter dimensions, and calculate total rib weight. The form uses a 3-column layout on large screens, 2-column on smaller, and 1-column on mobile.
Example data table
These examples are computed using the same formulas on this page.
| Example | Profile | Length each | Qty | Waste | Total (with waste) |
|---|---|---|---|---|---|
| Ribbed bar | Ribbed bar | 6.00 m | 20 | 3.0% | 195.08 kg |
| Flat bar | Flat bar | 5.00 m | 12 | 2.0% | 144.13 kg |
| Angle | Angle | 6.00 m | 10 | 5.0% | 338.27 kg |
| I-beam (approx.) | I-beam | 8.00 m | 6 | 2.0% | 1,183.75 kg |
Formula used
- Cross-section area (A): computed from the chosen profile geometry (mm^2).
- Unit weight: w = rho * A, where rho is density (kg/m^3) and A is in m^2.
- Piece weight: W_piece = w * L, where L is the length per piece (m).
- Total weight: W_total = W_piece * Q, where Q is quantity.
- Waste allowance: W_final = W_total * (1 + waste%).
- Cost estimate: Cost = W_final * UnitPrice (per kg in metric, per lb in imperial).
How to use this calculator
- Select your unit system and steel profile.
- Enter length, quantity, and waste factor.
- Fill the profile dimensions (or custom area).
- Optionally enter a unit price and currency.
- Press Calculate to view results above the form.
- Use Download CSV or Download PDF for reporting.
Material assumptions and density selection
Steel weight begins with density, typically 7850 kg/m^3 for carbon steel. Stainless grades trend higher, near 8000 kg/m^3, while low-alloy mixes can sit around 7700 kg/m^3. Use the custom option when mill certificates specify a different value, and keep the same density across a takeoff to avoid hidden variance.
Profile geometry and area estimation
The calculator converts dimensions into a cross-sectional area A. Round ribbed bars use A = pi d^2/4, flat bars use A = width x thickness, and L-angles use A approx t(a + b - t). Channel and I-beam areas are estimated with thin-wall sections, A approx (d - 2tf)tw + 2bf tf, which is suitable for quick site checks.
Length, quantity, and waste planning
Once unit weight is known, piece weight is unit_weight x length, then multiplied by quantity. A waste factor adds practical allowance for laps, cuts, bends, and off-cuts. Typical reinforcement waste ranges from 2% to 7% depending on detailing and stock lengths. For tight schedules, add a higher waste percentage to reduce reordering risk.
Unit handling for mixed projects
Metric inputs use millimeters and meters, while imperial inputs use inches and feet. Internally, the tool converts everything to metric to maintain consistent physics, then displays results in both systems. This helps when drawings, supplier quotes, and field measurements differ. Keep unit price aligned: per kg in metric mode or per lb in imperial mode.
Reporting, auditing, and cost control
Exporting results supports faster approvals and fewer transcription errors. Use CSV for spreadsheet tracking and PDF for signatures. When you enter unit price, the calculator estimates material cost with the waste allowance included, enabling quick comparisons across profiles, sizes, and procurement options. For auditing, store the export with the drawing revision and bar schedule date. Recalculate after design changes, especially diameter swaps or length changes, because weight scales linearly with both area and length, and cost follows directly.
FAQs
What does the calculator treat as a “steel rib”?
It estimates weight for common rib shapes used in construction takeoffs, including ribbed round bars and other steel profiles. Choose the closest cross-section and enter dimensions to get unit weight, piece weight, and totals.
Why do I see both kg/m and lb/ft in the results?
The tool converts inputs to metric internally, then reports unit weight in both systems for quick checks. This helps when drawings use metric but suppliers quote in imperial, or vice versa.
Are channel and I-beam results exact?
They are fast thin-wall estimates based on entered flange and web sizes. For procurement or final design, compare with manufacturer section tables because radii, tapers, and tolerances can shift area and weight slightly.
How should I pick a waste factor?
Start with 2–4% for straightforward cutting and minimal laps, 5–7% for complex detailing, and higher when stock lengths are limited. Track actual waste on site and update the factor for future takeoffs.
How is cost estimated?
Enter a unit price and currency. In metric mode, the price is applied per kilogram; in imperial mode, per pound. The estimate multiplies the waste-adjusted total weight by the unit price for a quick budget view.
Can I use custom area instead of dimensions?
Yes. If you already know the cross-sectional area from drawings or section properties, enter it directly. The calculator uses that area with density and length to compute weight without relying on geometry inputs.