Reinforcement Quantity Calculator — Longitudinal, Shear, and Wall Steel
Bidding, takeoff, and quantity-survey work all need accurate rebar weights. This calculator returns kg/m and total tonnage for any standard ASTM/PNS metric bar diameter, separately for longitudinal bars, shear stirrups, and wall reinforcement.
Formulas
| Quantity | Formula |
|---|---|
| Unit weight per metre (kg/m) | w = 0.006165 · d² (d in mm) |
| Standard metric bars | 10 mm: 0.617, 12: 0.888, 16: 1.578, 20: 2.466, 25: 3.853, 28: 4.834, 32: 6.313, 36: 7.99 kg/m |
| Stirrup length per piece | L_s = 2(b − 2c) + 2(h − 2c) + 2·hook (typically 75 mm × 2) |
| Number of stirrups | n = (clear span / spacing) + 1 |
How to use it
- Choose the member type: beam, column, or wall.
- Enter the cross-section dimensions and concrete cover.
- Add each rebar group: diameter, count, and length per bar.
- For shear reinforcement, enter the stirrup spacing — the calculator will compute number of stirrups and total wire length automatically.
- Read the per-bar-diameter summary plus a grand total in tonnes.
Frequently Asked Questions
Does this account for laps and waste?
No — the calculator gives you the as-built theoretical quantity. Add 5–10 % for laps and 3–5 % for waste depending on bar size and your detailing.
What unit weights does it use?
Theoretical weights from ASTM A615/A615M and PNS 49: 2002. The exact formula is w = 0.006165 · d² (mm to kg/m).
Can I use it for imperial bars?
It supports metric bars only (10 mm to 40 mm). For #3 to #11 imperial bars, use the equivalent metric size or your own per-bar weight.
Does it handle hooked bar lengths?
Yes for 90° and 135° standard hooks (12·d_b extension). For seismic hooks (135°, 6·d_b min), use the rebar hook calculator.