Rebar Calculator
Bars each way, the spacing you actually get, laps, stock and weight.
Grid
= 240" (20')
= 144" (12')
= 12" (1')
= 3"
Results update as you typeLive
Rebar · Result
CalculatedSTOCK PIECES
34 stock pieces to buy
- Lengthwise
- 13 bars · 12 bays
- Widthwise
- 21 bars · 20 bays
- Actual spacing
- 11 1/2" / 11 3/4"
- Weight
- 454.24 lb
Stock length defaults to 20' — UNVERIFIED trade default, not a sourced figure
SUGGESTED DEFAULTLap defaults to 40 bar diameters as a suggestion; the design lap is an engineer's number
SUGGESTED DEFAULTCode references & assumptions · 5
How this result is supported
- SUGGESTED DEFAULTStock length defaults to 20' — UNVERIFIED trade default, not a sourced figure
- PRIMARY-VERIFIED
- SUGGESTED DEFAULTLap defaults to 40 bar diameters as a suggestion; the design lap is an engineer's number
- PRIMARY-VERIFIED
- ASSUMPTIONWaste applies to length for pricing; piece counts come from geometry and laps only
- UNVERIFIED
- ASSUMPTIONBar areas use the nominal two-decimal ASTM A615 convention
- UNVERIFIED
- ASSUMPTIONActual spacing is equalised across the run; no bar is placed at more than the specified spacing
- CROSS-VERIFIED
What do these evidence labels mean?
- PRIMARY-VERIFIED
- directly supported by one authoritative primary source, quoted with section/page/figure
- CROSS-VERIFIED
- independently supported by two or more appropriate authoritative sources
- DERIVED
- mathematically derived from PRIMARY-VERIFIED values; the derivation is preserved in data and in code
- INTERPRETED
- a source exists but translating it into calculator behaviour required interpretation
- CONVENTION
- recognised trade practice, not a mandatory provision
- ASSUMPTION
- product/design assumption or useful default with no authoritative basis
- UNVERIFIED
- insufficient authoritative evidence
Code references and product data are quoted in the units their source uses.
Reference checks are informational, not compliance determinations.
How rebar is calculated
Spacing is a maximum, not a target. The calculator fits whole bays across the clear span and then equalises them, so the spacing you get is at or below the spacing you asked for and no gap is oversized. The achieved figure is reported for each direction, because the two runs divide different spans and rarely land on the same number.
Bars are bays plus one: a grid at 12 in across a 10 ft clear span is ten bays and eleven bars, with a bar on each cover line. Counting bays and calling it the bar count is the classic off-by-one here, and it leaves an edge unreinforced.
Lap length and stock length are both shown and both editable. The lap is an engineer's decision — the calculator offers the common default and says so, and warns when a shorter lap is entered rather than silently accepting it.
bays = ceil(clear span ÷ spacing)
Whole bays across the span.
bars = bays + 1
One on each cover line, so both edges carry a bar.
actual spacing = clear span ÷ bays
Equalised, so no bar sits further apart than you asked for.