A Beginner’s Guide to Rebar Types, Sizes, and Grades

Rebar (reinforcing bar) is a steel bar used to make concrete stronger, especially under tension. Fiberglass rebar is sometimes used because it does not rust and is non-magnetic.

Rebar comes in many sizes, grades, and types to suit different construction needs. Sizes can differ between countries, with metric and imperial measurements being the most common. 

In the U.S., standards are set by organizations like the American Concrete Institute (ACI) and ASTM (American Society for Testing and Materials).

In this guide, we’ll focus on imperial rebar sizes, which are standard in the U.S., following ASTM A615/A615M specifications for carbon steel bars used in concrete reinforcement.

Rebar Sizes

Here are common uses for each of the steel rebar sizes:

#3 — This thin and affordable mild steel rebar strengthens concrete driveways, roads or patios. It is also used in swimming pools to provide the pool walls with shape and strength.

#4 — This rebar adds strength to highways, columns, and slabs.

#5 — This rebar is commonly used for bridges and highways.

#6 — This rebar strengthens foundations, retaining walls, and roads or highways.

#7 — This rebar supports structures such as multi-storey parking garages and bridges.

#8 — This rebar is ideal for commercial slabs, columns, beams, and sea walls.

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#9 — This rebar is strong and perfect for high-rises, sea walls, and retaining walls.

#10 — This rebar is ideal for commercial beams, columns, and structural support.

#11 — This rebar is thick and strong, so it is often used for load-bearing structures.

#14 — The #14 rebar is a thick, heavy-duty choice for bridges, buildings, and docks.

#18 — This large, strong rebar is used for industrial and large-scale buildings.

Rebar Grades

Understanding the difference between yield strength and tensile strength is key when picking the right rebar.

Think of yield strength as the point where the steel starts to bend permanently, and tensile strength as the maximum stress the steel can withstand before breaking.

Rebar grades, set by ASTM standards, are based on minimum yield strength measured in KSI. Common grades include 40, 60, 75, 80, and 100. 

The number tells you how strong the rebar is: grade 40 can handle 40 KSI (40,000 PSI) before bending, while grade 80 holds up to 80 KSI (80,000 PSI).

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