Rebar Calculator — m, kg, cost
How to use this calculator
Pick an input mode that matches your takeoff: Area + Spacing for slab and wall mats (sized for a square equivalent), Total Length for footing runs and bar-schedule totals, or Quantity + Length for links, dowels, and cut lists. Bar diameters Ø6 through Ø32 mm, lap splices per Eurocode 2, waste 0–25%. Tap a preset above the input mode to load typical jobsite numbers.
Lap splices default to 40·db (good bond); switch to 50·db for poor bond conditions per EN 1992-1-1 §8.7.
Cost — price per linear metre, per kilogram, or per stock bar; pick EUR, PLN, CZK, SEK, GBP, or CHF.
Tying wire — about 1.2 kg of 1.2 mm black annealed wire per 100 intersections.
Saved Calculations
| Time | Bar | Mode | Length m | Bars | Weight kg | Cost |
|---|
How to Use This Metric Rebar Calculator
Choose the input mode for your takeoff. Area + Spacing builds a square mat from the slab/wall/footing area and the on-centre spacing each way (bars = side ÷ spacing + 1, both directions, × layers). Total Length works from a bar schedule in metres. Quantity + Length suits links, dowels, and cut lists. Unit masses are B500B (EN 10080) nominal: Ø8 = 0.395, Ø10 = 0.617, Ø12 = 0.888, Ø16 = 1.578, Ø20 = 2.466, Ø32 = 6.313 kg/m. Steel density is 7850 kg/m³. Size the footing or grade-beam volume first with the concrete beam calculator (m, m³, rebar) and the concrete bag calculator.
Formulas
Net length is computed per mode, then splices and waste are added: lap length = 40·db for good bond conditions, or 50·db for poor bond, consistent with EN 1992-1-1 §8.7 design lap length l0 (the calculator uses the simplified diameter multiple; a full l0 also depends on α coefficients, bond, and lapped percentage). Laps per run = ceil(net ÷ stock length) − 1. Total = (net + laps × lap) × (1 + waste%). Bar count = ceil(total ÷ stock length); mass = total × kg/m; tonnes = kg ÷ 1000.
Ordering tips & jobsite notes
Rebar across Europe in 2025 runs roughly €0.80–€1.50/kg at the yard for B500B, or about €0.50–€3.00/m depending on diameter — small jobs pay the high end because of cut-and-bend minimums. The single biggest takeoff mistake is forgetting the lap: a 12 m Ø12 bar only nets ~11.5 m of in-place steel after a 40·db (480 mm) splice, so a 30 m footing run is closer to 33–35 m ordered, not 30. Other things that bite estimators: dowels and corner bars not on the schedule, double-tied perimeters doubling wire use, and Ø10 vs Ø12 mix-ups (a Ø12 is 44% heavier per metre than a Ø10). For structural members, cross-check section masses with the steel beam weight calculator and connections with the bolt pattern calculator (mm, kN); column reinforcement ties into the steel column calculator and embed plates feed the steel plate weight calculator.
FAQ
Why does ordered length exceed in-place length? Each splice adds 40·db (or 50·db) of bar and the waste factor is applied on top. Does area mode include cover? It adds one perimeter bar per direction but does not deduct concrete cover — verify against the reinforcement drawings. Is this a full EC2 lap design? No — it uses the common 40/50·db rule of thumb for quantities; detailed splice design must follow EN 1992-1-1. Embed plate steel can be checked with the steel plate weight calculator.
