Rebar calculator — weight per length and total weight

Every rebar weight table is built on the same idea: the density of steel, 7,850 kg/m³, applied to the bar’s nominal cross-section. In metric sizes that boils down to weight per meter = 0.00617 × d², where d is the diameter in millimeters — so a ø12 bar weighs 0.888 kg/m and a 6 m length just under 5.4 kg. US bar sizes (#3–#10) are numbered in eighths of an inch and carry nominal weights per ASTM A615; switch the calculator to US units to work in lb per foot.

Bars are typically sold in stock lengths — 6 or 12 m in Europe, 20, 40 or 60 ft in the US — with cut-and-bent bars ordered from the bar bending schedule. Remember that lap splices, tie wire and spacers all come on top of the theoretical weight, so the ordered tonnage is always higher than the calculated one.

For slabs on grade, walls and toppings, welded wire mesh is usually the fastest way to place reinforcement. The calculator works with a common European stock sheet of 2.35 × 5.0 m (11.75 m²) at 150 mm spacing, in ø5 (about 2.1 kg/m²), ø6 (about 3.0 kg/m²) and ø8 (about 5.3 kg/m²). Sheets are lapped by at least one mesh spacing — never less than 300 mm — so plan on 10–15% more area than the floor you are covering.

Need a quantity before the engineer has finished the design? Normal cast-in-place structures often land around 80–120 kg of reinforcement per m³ of concrete. Use that for budgets and bids — never for ordering. The final quantity always comes from the bar bending schedule in the structural documents.