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Rebar Calculator

Calculate total rebar length, weight, bar counts, laps, and cost estimate for slabs and walls. Supports bar sizes #3 through #10 with per-size weight lookup.

Layout Grid Description

Rebar is typically laid in a two-way grid pattern. Bars run parallel to the length and width of the slab. The spacing between bars determines the structural strength — tighter spacing means more steel and greater load capacity. For slabs on grade, a 12" grid with #4 or #5 rebar is common. Structural slabs may require 6" spacing with larger bars.

'What is a rebar lap splice?', 'answer' => 'A lap splice is where two bars overlap to transfer load between them. Standard lap length is typically 40–60 bar diameters. The 10% extra material allowance in this calculator accounts for typical lapping requirements.'], ['question' => 'How deep should rebar be placed in a slab?', 'answer' => 'Rebar should be placed in the middle third of the slab thickness, typically with 1.5"–2" of concrete cover on all sides to protect against corrosion and fire.'], ['question' => 'What is the difference between deformed and plain rebar?', 'answer' => 'Deformed rebar has ribs that improve bonding with concrete. Plain (smooth) rebar is rarely used in structural applications. All common US rebar (ASTM A615/A706) is deformed.'], ]" />

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