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Rebar Weight Calculator

Estimate the weight of rebar needed for your concrete project.

How it is calculated

The tool uses the common rule of thumb weight per metre = d² ÷ 162 in kg/m, where d is the nominal bar diameter in millimetres. Total length is length × quantity in metres, and total weight is (d² ÷ 162) × total length in kilograms. The 162 comes from steel at about 7,850 kg/m³ and a round cross-section, so it assumes a plain round bar of that nominal diameter; ribs, coatings and mill tolerances can move real weights by a small amount. Diameter and length must be above zero; if the quantity is left empty or is zero or negative, the tool treats it as one bar. The per-metre value is rounded only for display, and the total is computed from the unrounded figure.

Worked example

An order of 50 bars of 12 mm rebar, each 12 m long. Step 1: weight per metre = 12² ÷ 162 = 144 ÷ 162 = 0.89 kg/m (0.8889 before rounding). Step 2: total length = 12 × 50 = 600.00 m. Step 3: total weight = 0.8889 × 600 = 533.33 kg. That is a little over half a tonne of steel for the order.

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Common mistakes

  • Entering the diameter in centimetres or inches; the formula is built for millimetres, so 1.2 instead of 12 gives a weight 100 times too small.
  • Entering the length in millimetres or feet instead of metres.
  • Entering the total number of metres in the length field and also a quantity, which multiplies the length twice.
  • Leaving the quantity at zero and reading the answer as the total, when the tool then treats it as one bar.
  • Using the result as a delivery weight without allowing for cut-offs, laps and bends in the reinforcement schedule.

About this calculator

This calculator estimates the weight of steel reinforcement bar (rebar) using the standard construction formula weight per meter = d²/162 kg, where d is the bar diameter in millimeters. Multiplying by the bar's length and the number of bars gives the total steel weight needed for a job.

Civil engineers, site supervisors, and steel suppliers use this shortcut — derived from steel's density of 7850 kg/m³ — to quickly price out reinforcement for slabs, columns, and footings without weighing bars on site.

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Comments (1)

  • Editorial team

    Compare the per-metre figure with a supplier's weight table. 8 mm should come to about 0.395 kg/m, 10 mm about 0.617, 12 mm about 0.889, 16 mm about 1.58 and 20 mm about 2.47. If a quoted weight is far from these, check the bar diameter or the unit. Nominal sizes in other standards are not converted here. Which bar sizes or standards do you work with?

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