Rebar Calculator — ft, lbs, cost
How to use this calculator
Pick an input mode that matches your takeoff: Area + Spacing for slab and wall mats (sized for square equivalent), Total Length for footing runs and bar-schedule totals, or Quantity + Length for stirrups, dowels, and cut lists. Bar sizes #3 through #11, lap splices per ACI 318-19, and waste 0–25%. Tap a preset above the input mode to load typical jobsite numbers.
Lap splices use Class B tension (40·db) by default; switch to Class A (30·db) only when ≤50% of bars are spliced and excess reinforcement is provided.
Cost — price per linear foot, per pound, or per stock bar.
Tying wire — about 2.5 lb of 16-gauge black annealed wire per 100 intersections.
Saved Calculations
| Time | Bar | Mode | Length lf | Bars | Weight lbs | Cost |
|---|
How to Use This Rebar Calculator
Pick the input mode that matches your takeoff. Area + Spacing approximates a square mat from the slab/wall/footing area and the on-center spacing in each direction (bar count = side ÷ spacing + 1, both ways, × layers) — fast for slabs-on-grade and footing mats. Total Length is for bar schedules where you already have linear footage. Quantity + Length suits stirrups, dowels, and cut lists. Unit weights are ASTM A615 Grade 60 nominal: #3 = 0.376, #4 = 0.668, #5 = 1.043, #6 = 1.502, #8 = 2.670, #11 = 5.313 lb/ft. Steel density is 490 pcf. For a footing or grade-beam takeoff start from the concrete beam calculator (ft, yd, rebar), then size mix volume with the concrete bag calculator.
Formulas
Net length is computed per mode, then splices and waste are added: lap length = 40·db (ACI 318-19 §25.5 Class B tension; the 30·db option is the Class A condition where ≤50% of bars are spliced and excess reinforcement is provided). Laps per run = ceil(net ÷ stock length) − 1. Total = (net + laps × lap) × (1 + waste%). Bar count = ceil(total ÷ stock length); weight = total × lb/ft; tons = lbs ÷ 2000.
Ordering tips & jobsite notes
Rebar in 2025 USA runs roughly $0.50–$1.20/lb at the yard (Gr 60), or about $0.30–$1.50/lf depending on size — small jobs pay the high end because of cut-and-bend minimums. The single biggest takeoff mistake is forgetting the lap: a 20-ft #5 bar only nets ~18.7 ft of in-place steel after a 40·db (25″) Class B splice, so a 100-ft footing run is closer to 110–115 ft ordered, not 100. Other things that bite estimators: dowels and corner bars not on the schedule, double-tied perimeter doubling wire use, and #4 vs #5 mix-ups (a #5 weighs 56% more per foot than a #4). For structural members, cross-check section weights with the steel beam weight calculator and connection layouts with the bolt pattern calculator; column reinforcement ties into the steel column calculator and embed plates feed the steel plate weight calculator.
FAQ
Why is the bar count higher than length ÷ stock length? Each splice consumes 40·db of bar, and the waste factor is applied on top, so ordered footage exceeds the bare in-place length. Does the area mode account for cover and edge bars? It adds one bar beyond the clear span in each direction (perimeter bar) but does not deduct concrete cover — confirm against your reinforcement drawings. Which lap class should I use? Class B (40·db) is the default for tension splices; use Class A only when code conditions are met. Embedded steel weight also feeds the steel plate weight calculator for embed plates.
