Construction
Rebar calculator
Rebar orders are counted in sticks and weighed in pounds, but the slab only cares about spacing. Enter the slab dimensions, bar spacing, and bar size, and this calculator counts the bars in both directions, totals the linear feet with a lap allowance for splices, and converts that to 20-foot sticks and total weight using standard ASTM bar weights. #4 bars at 18 inches on center is the workhorse spec for residential slabs — adjust if your plans say otherwise.
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Rebar Calculator
Count rebar bars, linear feet, sticks, and weight for a reinforced concrete slab.
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Tie wire & pliersBar count done — tie wire and a twisting tool hold the grid while you pour.Paid link · Check current price ↗As an Amazon Associate I earn from qualifying purchases.The math, plainly
How it works
- 01
Bars in each direction are the span in inches ÷ spacing, plus one extra for the far edge, rounded up.
- 02
Total bar length adds both directions plus a lap allowance for the overlaps where bars splice together.
- 03
Weight uses standard bar weights — #3 is 0.376 lb/ft, #4 is 0.668, #5 is 1.043 — and sticks are total feet ÷ stock length, rounded up.
Try a real scenario
20 × 24 slab
Inputs#4 bars at 18 in, 10% lap, 20-ft stock
Result15 bars one way and 17 the other — about 770 linear ft, 39 sticks, roughly 514 lb.
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Steel only works in the middle of the slab — chairs hold it off the ground at the right height.
Angle finder (paid link)
Sets the pitch on ramps and aprons so the grid follows the pour instead of fighting it.
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Cuts and hooks #4 bar without the spark-show of an angle grinder.
As an Amazon Associate I earn from qualifying purchases.