Rebar Calculator

Free rebar calculator. Estimate rebar count, total linear feet, weight, and cost for concrete slabs, driveways, and foundations. Covers #3, #4, #5, #6, and.

#3 (3/8 in)

$0.30–$0.55/ft

0.376 lb/ft

#4 (1/2 in)

$0.45–$0.75/ft

0.668 lb/ft

#5 (5/8 in)

$0.75–$1.20/ft

1.043 lb/ft

#6 (3/4 in)

$1.10–$1.80/ft

1.502 lb/ft

Slab Dimensions

Rebar & Pricing

Rebar Size & Price Reference

SizeDiameterWeight (lb/ft)Price range (/ft)Common use
#33/8 in0.376$0.30–$0.55Light sidewalks, ties
#41/2 in0.668$0.45–$0.75Driveways, patios, slabs
#55/8 in1.043$0.75–$1.20Structural footings, walls
#63/4 in1.502$1.10–$1.80Heavy footings, columns
#81 in2.670$2.00–$3.20Commercial, structural

Frequently Asked Questions

How much does rebar cost per foot?

#4 rebar (1/2 inch, the most common size) costs $0.45–$0.75 per linear foot at home improvement stores. #3 rebar runs $0.30–$0.55/ft and #5 costs $0.75–$1.20/ft. Prices vary by region and steel market conditions. Buy from a steel supplier for large projects to save 20–40% vs retail.

How much rebar do I need for a 20x20 slab?

A 20×20 ft slab (400 sq ft) with #4 rebar on 12-inch spacing needs about 820 linear feet of rebar, or 41 twenty-foot sticks. That covers both directions (21 bars each way × 20 ft each). Add 10% waste for cuts and overlaps.

What size rebar should I use for a concrete slab?

#4 rebar (1/2 inch diameter) at 12-inch spacing is standard for residential driveways and patios. Use #3 at 12-inch spacing for light sidewalks. For structural footings, garage floors, or driveways under heavy vehicles, use #4 or #5 at 12-inch spacing — always confirm with local code requirements.

How do you calculate rebar for a slab?

Divide the slab width by spacing, add 1 to get the number of bars running in one direction. Multiply by the slab length to get linear feet for that direction. Repeat for bars running the other way. Add the two totals, then add 10% for waste and lap splices.

How much does rebar weigh per foot?

#3 rebar weighs 0.376 lb/ft, #4 weighs 0.668 lb/ft, #5 weighs 1.043 lb/ft, #6 weighs 1.502 lb/ft, and #8 weighs 2.670 lb/ft. Multiply by your total linear feet to get the total weight, which helps estimate delivery and handling.

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