CONSTRUCTION CALCULATORS / PROJECT ESTIMATOR

Rebar Calculator

Estimate rebar grid bar counts and total linear feet from slab dimensions, spacing and waste. Review cover, lap lengths and design limitations.

Inputs to confirm: slab dimensions, bar spacing, cover, lap lengths and bar stock lengths.

Estimate a two-direction rebar grid

Enter slab length and width in feet and the specified bar spacing in inches. This tool estimates a rectangular grid using full slab dimensions. It does not choose the required bar size, grade or spacing, and it does not reduce runs for concrete cover.

Bar counts and linear-foot formula

Bars running along the slab length = floor(width × 12 ÷ spacing) + 1. Bars running along the width = floor(length × 12 ÷ spacing) + 1. Total length = the sum of both bar counts multiplied by their respective runs, then multiplied by (1 + waste ÷ 100).

For a 10 × 12 ft slab with 12-inch spacing, there are 13 runs of 10 ft and 11 runs of 12 ft: 130 + 132 = 262 linear ft. A 10% allowance gives 288.2 linear ft.

Rebar questions

Is this a structural reinforcement design?

No. Use the project’s reinforcement schedule. Cover, edge distances, laps, hooks, dowels and development lengths must come from the applicable design.

How many stock bars should I buy?

Divide the required cut lengths into available stock lengths using a cutting schedule. Dividing total linear feet by stock length alone can miss unusable offcuts and required laps.

Does waste include lap splices?

The percentage is only a general allowance. The tool does not calculate splice lengths or positions. Add designed laps explicitly in a detailed takeoff rather than assuming a percentage proves adequacy.

Plan the slab separately

Use Concrete Slab for concrete volume, Concrete Slab Cost for illustrative budget allowances and Gravel for the separately specified base.

Calculation and guidance updated October 28, 2026. Report a suspected error through Contact, including your inputs and expected result.