Rebar Length and Theoretical Mass Calculator

Choose a nominal bar diameter, unit, and mode. Straight-bar mode multiplies one bar length by its quantity and tabulated mass per meter. Grid mode assumes a rectangular, single-layer, two-direction layout with straight bars at both boundaries; you supply the maximum center-to-center spacing. The tool calculates a takeoff, not a reinforcement design or a code-compliance judgment.

For ten 6 m bars of nominal 10 mm diameter, length is 60 m and theoretical mass is 60 × 0.617 = 37.020 kg. Each bar is 3.702 kg by the rounded table value. No lap, bend, hook, or cutting allowance is included.

The selector uses these rounded metric mass-per-meter values. A theoretical density of about 7,850 kg/m³ is a common basis for steel calculations; Steel Construction Institute data uses that density. Check your actual bar specification and supplier mass when ordering.

The Concrete Reinforcing Steel Institute describes nominal bar properties. These metric choices are not a conversion to U.S. bar designations.

Total length = one bar length × integer quantity. Theoretical mass = total length in meters × selected table kg/m. Conversions are exact length conversions: 1 mm = 0.001 m, 1 cm = 0.01 m, 1 in = 0.0254 m, and 1 ft = 0.3048 m. The table mass is rounded, so the output is an estimate rather than a certified product weight.

For a smooth ideal cylinder, mass per meter is approximately π × (diameter in meters / 2)² × 7,850 kg/m³. With 10 mm, that is about 0.6165 kg/m, rounded to the calculator's 0.617 kg/m. Real reinforcing bars have deformations and manufacturing tolerances; use product data when precision matters.

Grid mode uses your maximum center spacing S, not a spacing selected by this page. For each span D, it computes ceil(D / S) intervals and one bar at each endpoint. The bars are evenly positioned, so actual center spacing is D / ceil(D / S), no greater than S. Along the length the counted bars span the width, and vice versa.

For 10 × 5 m and an entered 0.2 m maximum, the count is (ceil(10 / 0.2) + 1) + (ceil(5 / 0.2) + 1) = 51 + 26 = 77 bars. Length is 51 × 5 + 26 × 10 = 515 m; at 0.617 kg/m, theoretical mass is 317.755 kg. This assumes bars at the rectangle boundaries, which may not match the placement lines in structural drawings.

The calculator does not determine suitable spacing, concrete cover, strength, layers, or support detailing. Those depend on loads, geometry, materials, and the applicable design.

Use the arithmetic to check a straight-bar list or count a simple rectangular grid already defined on drawings. For beams, columns, foundations, walls, and slabs, the geometry and reinforcement arrangement must come from the project design. The calculator does not infer those arrangements from the element name.

Compare the takeoff with the bar schedule, cover lines, cut lengths, bends, hooks, laps, splices, multiple layers, openings, and available stock lengths. None is added automatically. Do not apply a universal lap or waste percentage: the CRSI splicing guidance describes several design variables for lap length, and cutting waste depends on a real schedule. Source pages checked 29 September 2026.