Rebar Area Calculator (Ast)

Find the area of steel in a section. Enter the bar size and number of bars to get the area of one bar and the total Ast, and optionally the steel percentage of a given section.

0

How to use: Rebar Area Calculator

Pick the bar size and number of bars.
Optionally enter the section width and depth.
Read Ast and the steel percentage.

Formula

Area of one bar = π/4 × d². Ast = number of bars × area. Steel % = Ast ÷ (b × D) × 100.

See the full rebar weight chart (kg/m & lb/ft) →

Rebar Area Calculator — FAQ

What is the area of a 12mm rebar?

π/4 × 12² ≈ 113.1 mm² per bar.

What is Ast in reinforcement?

Ast is the total cross-sectional area of tension steel in a section.