Rebar Weight Calculation Formulas: Standard US & Metric Sizes

Reinforcing bar (rebar) weight calculations are a daily task in concrete construction bidding. Rebar is ordered by total weight, making accurate length-to-weight estimates essential for cost planning.

The D²/162 Shortcut Formula

For metric measurements, engineers use a standard shortcut formula to calculate the weight of a steel rebar per meter of length:

$$\text{Weight (kg/m)} = \frac{D^2}{162.2}$$

Where (D) is the nominal diameter of the reinforcing bar in millimeters. For example, to calculate the weight per meter of a 12 mm rebar: (12^2 \div 162.2 = 144 \div 162.2 = 0.888 \text{ kg/m}). If you have a bundle of 50 rebars, each 12 meters long, the total weight is calculated by multiplying the weight per meter by the total length.

US Imperial Rebar Sizing

In the United States, rebar is sized by "bar numbers" (e.g., #3 to #18). The diameter of the bar is calculated by dividing the bar number by 8 inches. A #4 bar has a diameter of 0.5 inches, and its weight is approximately 0.668 pounds per foot.

Calculate custom rebar weights using our interactive length to weight steel calculator. For sheet metal projects, refer to our sheet metal thickness gauge chart.