Concrete reinforcing bar, commonly called rebar, is the steel embedded in concrete to resist tensile forces. Concrete is very strong in compression but weak in tension, which makes reinforcing bar the decisive factor in a structure's strength. This guide covers types, sizes, weight tables, and how to calculate what your project needs.

Two Types: Plain and Deformed

1. Plain bar (BjTP). A smooth surface without ribs, generally used for stirrups, secondary reinforcement, and non-structural elements. The common grade is BjTP 280.

2. Deformed bar (BjTS). A ribbed surface that greatly improves bond with concrete, allowing far better force transfer. Used as main reinforcement in columns, beams, slabs, and foundations. Common grades are BjTS 420 and BjTS 550.

In multi-storey structures both are typically used together: deformed bars as main reinforcement, plain bars as stirrups.

Reinforcing Steel Grades

The grade is set by the structural designer's calculation, not by what happens to be in stock. Downgrading without recalculation directly reduces structural capacity.

Sizes and Weight Tables

Deformed Bar

Plain Bar

The underlying formula is weight per metre = 0.006165 × d², where d is the diameter in millimetres — a quick way to sanity-check any delivery.

How to Calculate Requirements

1. Total the required bar length per diameter from the drawings.
2. Add lap splices and bends, typically 5–10%.
3. Multiply total length by weight per metre.
4. Divide by weight per bar to get the number of bars to order.

Example: a column needs 480 m of D16 in total. With 8% for laps, that becomes 518 m. Weight is 518 × 1.578 kg = 817 kg. At 18.94 kg per 12 m bar, about 44 bars are required.

Always round up and allow a small margin for offcuts.

Checking Quality on Delivery

Look for embossed marking showing mill initials, diameter, and grade.
Weigh bars at random and compare against the table above.
Measure the diameter with a caliper; on deformed bars, measure the core between ribs.
Request the mill certificate with tensile, bend, and chemical composition results.
Inspect physically for longitudinal cracks, laps, or flaking rust.

Common Mistakes on Site

Buying by price per bar. A cheaper bar is often lighter because its diameter was reduced. Compare price per kilogram instead.

Substituting diameters. Replacing D16 with D13 cuts the cross-sectional area by roughly 34% — a severe loss of capacity.

Storing bars directly on the ground. Contact with damp soil accelerates corrosion. Use timber dunnage and cover with tarpaulin.

Ignoring lap length. Short laps prevent proper force transfer between bars.

Frequently Asked Questions

What is the difference between plain and deformed bar?
Plain bar is smooth and mainly used for stirrups; deformed bar is ribbed for far stronger bond and serves as main reinforcement.

What is the standard bar length?
Generally 12 metres. Other lengths can be produced to project requirements.

How do I confirm the bar meets standard?
Check the embossed marking, weigh and compare against the weight table, and request the mill certificate.

Can I buy reinforcing bar directly from the mill?
Yes. Buying direct provides quality assurance at source and pricing without layered intermediary margins.

Reinforcing Bar From Inter World Steel

PT Inter World Steel Mills Indonesia is a steel mill in Tangerang producing SNI-certified plain and deformed concrete reinforcing bar, with over 50 years of experience serving contractors, distributors, and export markets. Every delivery includes a mill certificate and guaranteed true weight.

For factory-direct pricing, contact our sales team via the Order Now page.