Rebar Weight Calculator

This calculator computes the mass of reinforcing steel (rebar) using the geometric cross-section and material density. It returns weight per metre, weight for a single bar (given its length), and total mass for a specified count of bars.

Calculations use SI units: diameter in millimetres, length in metres, and density in kilograms per cubic metre. The default density (7850 kg/m³) is the commonly used nominal value for carbon steel; adjust if you are using stainless or FRP rebar.

Updated Nov 9, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record 5caad0809338 • Reviewed by Fidamen Standards Committee

Inputs

Rebar diameter (mm)

Min 3 · Max 80

Length of each bar (m)

Min 0.01 · Max 100

Number of bars

Min 1 · Max 100000

Steel density (kg/m³)

Min 7000 · Max 8100

Results

Updates as you type

Weight per metre

15,700

Weight per bar (single length)

94,200

Total weight (all bars)

94,200

Total weight (tonnes)

94.2

Output	Value	Unit
Weight per metre	15,700	kg/m
Weight per bar (single length)	94,200	kg
Total weight (all bars)	94,200	kg
Total weight (tonnes)	94.2	t

Primary result15,700

Visualization

Points

Methodology

We compute cross-sectional area from the nominal diameter using the circle area formula, then multiply by length and material density to obtain mass. This follows standard material-property methods used in structural engineering and materials science.

Default material density is set to 7850 kg/m³. If you have manufacturer data or a materials standard for a specific grade, replace the density value to reflect that specification.

For field use, measure length with calibrated tape measures and confirm diameter against manufacturer labels or inspection gauges. Small measurement errors in diameter propagate quadratically into mass, so diameter accuracy is especially important.

F.A.Q.

Why does diameter accuracy matter more than length accuracy?

Cross-sectional area depends on the square of diameter. A 1% error in diameter produces roughly a 2% error in area and thus mass, whereas a 1% error in length produces a 1% error in mass.

What density value should I use for different rebars?

7850 kg/m³ is the standard nominal density for most carbon steels. Use manufacturer or material-certification data for stainless, epoxy-coated, or FRP bars. If uncertain, consult material test reports or standards from recognized bodies.

Can I enter lengths in feet?

This calculator expects length in metres. Convert feet to metres by multiplying by 0.3048. Guidance and conversion links are provided in the citations below.

How accurate are the results for procurement and shipping?

This tool provides engineering-level estimates adequate for takeoffs and early procurement. Final ordering and shipping weights should use manufacturer-supplied weights, mill certificates, or weighbridge measurements to account for tolerances, coatings, and bundling.

Do coatings or ribbing affect the calculated weight?

Light coatings (e.g., epoxy) add small additional mass; heavy galvanizing or coatings may be significant. Ribbing geometry is already included in nominal diameter where the listed diameter is an equivalent (manufacturers often provide actual mass per metre). For highest accuracy, use manufacturer mass-per-length data.

How should I verify the tool on-site?

Compare calculator outputs with known samples: measure diameter with calipers, measure length, then weigh a single known-length sample on a calibrated scale. Differences larger than expected manufacturing tolerances should prompt a review of inputs or the use of mill-certified weights.

Sources & citations

NIST - Reference Materials and Data — https://www.nist.gov/srd
MIT OpenCourseWare - Materials Science resources — https://ocw.mit.edu
U.S. Occupational Safety and Health Administration (OSHA) - Handling and storage of construction materials — https://www.osha.gov
International Organization for Standardization (ISO) - standards and technical guidance — https://www.iso.org
ACI — American Concrete Institute Standards — https://www.concrete.org/publications/typesofpublications/standards(codesandspecs).aspx
ACI 211.1-91 — Standard Practice for Selecting Proportions for Concrete — https://www.concrete.org/
ASTM International — Construction Standards — https://www.astm.org/

Further resources

Related tools

Versioning & Change Control

Audit record (versions, QA runs, reviewer sign-off, and evidence).

Record ID: 5caad0809338

What changed (latest)

v1.0.0 • 2025-11-09 • MINOR

Initial publication and governance baseline.

Why: Published with reviewed formulas, unit definitions, and UX controls.

Public QA status

PASS — golden 25 + edge 120

Last run: 2026-01-23 • Run: golden-edge-2026-01-23

Engine

v1.0.0

Data

Baseline (no external datasets)

Content

v1.0.0

Governance

Last updated: Nov 9, 2025

Reviewed by: Fidamen Standards Committee (Review board)

Credentials: Internal QA

Risk level: low

Reviewer profile (entity)

Fidamen Standards Committee

Review board

Internal QA

Entity ID: https://fidamen.com/reviewers/fidamen-standards-committee#person

Semantic versioning

MAJOR: Calculation outputs can change for the same inputs (formula, rounding policy, assumptions).
MINOR: New features or fields that do not change existing outputs for the same inputs.
PATCH: Bug fixes, copy edits, or accessibility changes that do not change intended outputs except for previously incorrect cases.

Review protocol

Verify formulas and unit definitions against primary standards or datasets.
Run golden-case regression suite and edge-case suite.
Record reviewer sign-off with credentials and scope.
Document assumptions, limitations, and jurisdiction applicability.

Assumptions & limitations

Uses exact unit definitions from the Fidamen conversion library.
Internal calculations use double precision; display rounding follows the unit's configured decimal places.
Not a substitute for calibrated instruments in regulated contexts.
Jurisdiction-specific rules may require official guidance.

Change log

v1.0.0 • 2025-11-09 • MINOR

Initial publication and governance baseline.

Why: Published with reviewed formulas, unit definitions, and UX controls.

Areas: engine, content, ui • Reviewer: Fidamen Standards Committee • Entry ID: 42222a60f83d