Rebar Weight Table and Guide to Checking Actual Weight Upon Delivery

Suppose a truck has brought you بیست شاخه rebar, size ۱۸, and the invoice says the total weight of the load is ۴۸۰ کیلوگرم. Is this number reasonable? Without a rebar weight table, the answer to this question is only a guess. With the table, the answer takes a few seconds, and those few seconds can save you from a loss-making deal.

Rebar is a commodity traded by weight, not by quantity

Unlike many goods that are bought and sold by the number of pieces, rebar is priced by weight. This means that every small difference between the actual weight and the claimed weight directly affects the final transaction price. The rebar weight table, also known in the market as the Stahlschlüssel table, is the reference that allows you to know the theoretical weight of each size in advance and avoid surprises when the load is delivered.

The calculation formula, and why it works this way

The weight of each meter of rebar is approximately obtained from the following relationship: raise the rebar diameter in millimeters to the power of two and divide it by ۱۶۲. This number, ۱۶۲, comes from two things: the geometry of the circular cross-section of the rebar and the density of construction steel, which is approximately ۷۸۵۰ کیلوگرم per cubic meter. When you combine these two, you arrive at a simple formula that gives you the approximate weight of each meter of rebar without needing an engineering calculator.

A complete example

For size ۱۸ rebar, the calculation proceeds as follows: ۱۸ squared is ۳۲۴; ۳۲۴ divided by ۱۶۲ equals ۲ کیلوگرم per meter. For a complete شاخه with a length of ۱۲ meters, which is the standard rebar length in the Iranian market, we multiply this number by ۱۲ and arrive at ۲۴ کیلوگرم. Now let us return to the first truck in this article: بیست شاخه multiplied by ۲۴ کیلوگرم equals ۴۸۰ کیلوگرم, exactly the number written on the invoice. If instead of ۴۸۰, the invoice showed ۴۲۰, this would be a significant difference worth asking about.

Weight of each ۱۲-meter rebar شاخه by size (کیلوگرم)

Source: Approximate rebar weight formula; diameter in millimeters squared, divided by ۱۶۲

On paper, everything is precise; the actual difference is always determined at the weighbridge.

Why the actual weight is never exactly equal to the table

The table weight is a theoretical figure based on the nominal diameter. The actual weight from each factory is slightly higher or lower than this figure because of small differences in the actual rolling diameter. For this reason, National Standard ۳۱۳۲ has defined an allowable range of deviation. The practical point is that each factory has its own official weight table, which may differ from the general formula above by a few grams; for precise transactions, ask the seller for that factory’s official table and use it as the benchmark, rather than an approximate number from the internet.

A few practical tips for when the numbers do not add up

• First of all, confirm the actual rebar size using the roll mark or a caliper; sometimes the weight difference results from a mistake in identifying the size, not under-delivery.
• Always compare the total weight of the load with the sum of the theoretical weight of each individual size, not with one overall average.
• If the load includes several different sizes, apply the table separately to each one so that calculation errors can be identified.
• A small difference within the allowable range is natural; a large, one-sided difference (always lower than the table) is a more serious sign.

Knowing this formula and table is more than just a mathematical trick; it is a common language that, in the rebar market, turns any disagreement between you and any seller or buyer into a discussable figure within a few seconds.