Rebar Calculator

Start with slab length, width, spacing, and bar size. Open advanced options for edge clearance, stock length, waste allowance, lap-splice factor, and wall / footing details.

Calculation mode

Use Slab grid for a flat rectangular mat, or switch to Wall / footing for horizontal courses and vertical bars.

Primary output 23 stock bars
Slab length in feet, or the horizontal wall / footing run in wall mode.
Slab width in feet. Wall / footing mode uses Wall height instead.
Vertical wall height or footing depth in feet for wall / footing mode.
On-center spacing in inches. In slab mode this applies to both directions; in wall mode it spaces vertical bars along the length.
Select the imperial bar size used for weight and lap-splice diameter.
On-center spacing in inches for horizontal courses across the wall height or footing depth.
Advanced options
Waste allowance Quantity takeoff only; engineered drawings control structural spacing and cover. Lap splice 20 in
This calculator computes with feet, inches, and U.S. rebar designations.
Planning context for presets; it does not change the grid count unless your drawings specify different spacing or cover.
Distance in inches from each slab edge to the first bar.
Length of each stock bar you plan to buy. The calculator rounds up to whole sticks.
Extra length for cuts, laps, and ordering buffer.
Field shorthand for lap length. Common takeoffs use 40–60 bar diameters; engineered splice schedules control permitted work.
Answer 23 stock bars
Lengthwise bars 11 bars
Widthwise bars 21 bars
Total rebar length 455.4 ft
Stock bars to buy 23 pieces
Approximate weight 304.21 lb
Lap-splice length 20 in
Show calculation details
Effective grid length 19.5 ft
Effective grid width 9.5 ft
Unit weight 0.668 lb/ft
Notes Quantity takeoff only; engineered drawings control structural spacing and cover.