Engineering Reference

Rebar Weight Calculator

Compute the weight of a rebar quantity from bar size and total length, and the number of bars needed for a given weight.

Page last changed 2026-10-19 · based on n/a — standard engineering relationships, no single governing revision

Quick Answer

Rebar weight per unit length scales with the square of the diameter. A #5 bar weighs 1.043 lb/ft; a #8 bar, with 1.6 times the diameter, weighs 2.56 times as much at 2.670 lb/ft.

Rebar Weight

The Formulas Used

weight per foot = (π/4) × d² × 0.2836 × 12
Bar number is the diameter in eighths of an inch for #3 through #8: d = number ÷ 8.

Weight Scales with Diameter Squared

Doubling the bar diameter quadruples the weight per unit length, because weight follows the cross-sectional area. That is why the step from #8 to #11 nearly doubles the weight per foot while the diameter rises by only 41%.

Weight is what rebar is bought and priced on, so it is the figure a takeoff needs. Use the rebar size chart for the tabulated values per bar size.

Where the Bar Number Breaks Down

The bar number is the diameter in eighths of an inch only up to #8. Above that the sizes were set separately, so #9 is 1.128 in rather than 1.125, and #14 is 1.693 in rather than 1.75. The calculator above uses the actual diameter, so it stays correct across the whole range.

Frequently Asked Questions

How much does #5 rebar weigh per foot?
1.043 lb/ft, or 1.552 kg/m. The bar is 0.625 in in diameter with a cross-sectional area of 0.307 in².
How do I calculate rebar weight?
Weight per foot = (π/4) × diameter² × 0.2836 × 12. Multiply by the total length for the job. Doubling the diameter quadruples the weight.
What size is #4 rebar?
#4 rebar is 0.500 in (12.7 mm) in nominal diameter. The bar number is the diameter in eighths of an inch for sizes up to #8.
How many #4 bars are in a ton?
At 0.668 lb/ft, a ton (2,000 lb) is about 2,994 ft of #4 bar — roughly 375 bars at 8 ft, or 250 at 12 ft.
Does rebar weight affect concrete cover?
Indirectly. Cover is specified as a distance from the concrete surface to the bar, so larger bars place their centre further in for the same cover. The governing requirement is in the applicable building code.

Related

Value Sources

References and calculation methods used for this page are listed below. Numbered markers connect table columns where present. A reference listing does not itself establish that every value has been independently checked.

#SourceTypeRevision / method
[1]ASTM A615 — Deformed steel bars for concrete reinforcementreferenceASTM A615/A615M-20 — source
[2]Values computed in your browserderivedEvaluated locally from the formulas shown on the page. No data leaves the device.

Data Sources

StandardRevisionWhat it covers on this page
Formulas as shown on this pagen/a — standard engineering relationships, no single governing revisionevery value this calculator produces

Verification scope

No page-specific independent source review is recorded here. The listed references and formulas explain the basis of the compilation; automated consistency checks do not verify the original sources or establish product conformity.

Derived values — the following values on this page are calculated, not taken directly from the standard:

ValueHow it is derived
All outputsComputed in the browser from the formulas above. No data leaves the device.

Outputs are computed from the formulas shown. Verify against the governing standard for design or acceptance work.

Accuracy and use. Use the source notes and recorded verification scope above to assess each value. Calculated values follow the stated derivations; compilation values may lack a confirmed original document or product condition. No warranty, express or implied, is made as to the accuracy or completeness of this information, and no liability is accepted for any loss or damage arising from its use. Engineering reference data is provided for guidance in preliminary work — before a value is used for design, fabrication or acceptance testing, verify it against the current revision of the governing standard and against your own inspection. The user assumes all risk and responsibility in connection with the use of this information.

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