Rebar Calculator — ft, lbs, cost
How to use this calculator
Choose an input mode: By Total Length (enter linear feet needed), By Area + Spacing (enter slab/wall area and bar spacing in both directions), or By Quantity + Length (enter number of bars and individual bar length). Select the bar size from #3 to #11 and set the standard bar length (typically 20 ft or 40 ft).
Lap splices are calculated at 40 bar diameters per ACI 318-19 (Class B tension splice). Waste allowance is adjustable from 0% to 25%.
Cost — price per linear foot, per pound, or per bar.
Tying wire — estimated at ~2.5 lbs per 100 intersections.
Saved Calculations
| Time | Bar | Mode | Length lf | Bars | Weight lbs | Cost |
|---|
How to Calculate Rebar Quantity
This rebar calculator estimates the total length, number of bars, weight, lap splices, and cost for reinforcing steel. Three input modes are supported: by area with bar spacing (for slabs, walls, and footings), by total linear footage, or by specifying a quantity and individual bar length. Bar sizes range from #3 (3/8 inch, 0.376 lb/ft) to #11 (1-3/8 inch, 5.313 lb/ft) per ASTM A615 Grade 60.
Lap Splices per ACI 318-19
When a single bar cannot span the full length, lap splices are required. Class B tension lap splice length is 40 bar diameters (40 d_b). For example, #4 bar (0.5" diameter) requires a 20-inch lap splice. The calculator accounts for the extra length consumed by each splice and adds it to the total.
Waste Allowance
Cutting waste varies from 5% for straight runs and standard lengths to 15-20% for complex shapes with many cuts and bends. The default 10% is suitable for most typical slab and footing applications.
Tying Wire
Rebar intersections are secured with 16-gauge black annealed tying wire. The calculator estimates approximately 2.5 pounds of wire per 100 intersections, which accounts for double ties and waste.
