Rebar Calculator — Fast Takeoffs for Slabs, Footings & Walls
Use this free Rebar Calculator to estimate the number of bars, total linear footage, and steel weight for common concrete elements. Choose Slab, Footing, or Wall, enter your dimensions, spacing, cover, and bar size, and get instant totals in both imperial and metric units. This tool is designed for quick takeoffs — always verify structural requirements with local codes or a licensed engineer.
What It Calculates
- Bar count in each direction/layer
- Total length by bar group and overall
- Total weight in pounds and kilograms
Quick Tips
- Edge offsets start the first bar in from the edge for better cover and spacing.
- Cover is the distance from concrete surface to the steel — common values: slabs 2″ bottom, footings 3″, walls 2″.
- For simple takeoffs, add a small waste allowance (e.g., 5–10%) for cuts and overlaps.
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FAQs
How do I calculate how much rebar I need for a slab?
Enter slab length and width, choose spacing, edge offset, and cover. The calculator returns the bar count in each direction, total length, and total weight.
What is the weight of #4 rebar per foot?
#4 rebar weighs approximately 0.668 lb per linear foot (~0.994 kg per meter).
Do I need to include lap splices?
This simple calculator focuses on takeoff for straight lengths. If you require laps, add a manual allowance or increase the waste factor. Always verify requirements with local code or an engineer.
Accuracy & Review
Reviewed by: Maria Ramirez, PE
Maria is a licensed Professional Engineer (PE) with experience reviewing residential and light commercial concrete quantity takeoffs. She reviewed the formulas, unit conversions, rounding rules, and default yield assumptions used in this calculator.
Last updated:
See: Methodology · Data Sources · Review Board
Important Estimate Disclaimer
Results are provided for general planning purposes only and do not constitute engineering or structural design advice. Actual material quantities may vary based on site conditions, reinforcement design, slab thickness, and local building code requirements.
See our Methodology and Data Sources for calculation details.
Subgrade preparation, load-bearing requirements, expansion joints, and curing conditions can significantly affect final concrete volume. Structural or frost-exposed installations should be reviewed by a qualified professional.