Concrete Stairs Volume Calculator

This calculator estimates the concrete required for a straight flight of poured stairs plus an optional landing. It models the stair flight as a triangular prism (side profile) and adds a rectangular landing when specified. Results include cubic feet, cubic yards, estimated weight, and a bag-equivalent.

Use the waste allowance to add a practical over-order percentage for site waste, slumping, finishing loss, or minor measurement uncertainty. Density and bag weight are configurable to reflect different concrete mix types or bag sizes.

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

Governance

Record a0d413bf95d1 • Reviewed by Fidamen Standards Committee

Inputs

Number of steps (total risers)

Min 1 · Max 200

Tread depth (run) per step (inches)

Min 3 · Max 36

Riser height per step (inches)

Min 3 · Max 12

Stair width (ft)

Min 0.5 · Max 20

Landing length (ft) — set 0 if none

Min 0 · Max 50

Landing slab thickness (inches)

Min 0 · Max 36

Waste / overage allowance (%)

Min 0 · Max 50

Concrete density (lb/ft³)

Min 80 · Max 200

Bag weight (lb) for bag-equivalent calculation

Min 1 · Max 200

Results

Updates as you type

Total horizontal run (ft)

5.8333

Total rise (ft)

4.375

Gross concrete volume (ft³)

38.2813

Volume including waste allowance (ft³)

42.1094

Concrete required (yd³)

1.5596

Estimated weight (lb)

6,316.4063

Number of bags (bag weight set below)

105

Output	Value	Unit
Total horizontal run (ft)	5.8333	ft
Total rise (ft)	4.375	ft
Gross concrete volume (ft³)	38.2813	ft³
Volume including waste allowance (ft³)	42.1094	ft³
Concrete required (yd³)	1.5596	yd³
Estimated weight (lb)	6,316.4063	lb
Number of bags (bag weight set below)	105	—

Primary result5.8333

Visualization

Points

Methodology

The flight is approximated as a triangular prism: the side-profile triangle has base equal to total horizontal run (steps × tread) and height equal to total rise (steps × riser). Volume = 0.5 × total run × total rise × stair width.

If a landing is present, it is modeled as a rectangular slab: volume = landing length × stair width × landing thickness. The calculator sums both volumes, applies a user-specified waste allowance, converts to cubic yards (1 yd³ = 27 ft³), and multiplies by concrete density to estimate mass.

Default density (150 lb/ft³) reflects normal weight concrete; adjust for lightweight mixes or high-density aggregates. Bag-equivalent is calculated by dividing total weight by the bag weight entered.

F.A.Q.

Why is the stair modeled as a triangle?

A monolithic poured stair flight forms a triangular side profile when risers stack progressively. Modeling the side profile as a triangle and extruding by stair width yields a reliable volume estimate for solid stairs. Use the landing slab addition for flat landings.

What waste percentage should I use?

Common practice is 5–15% depending on site conditions, finishing losses, and mix handling. For complex forms or heavy reinforcement, choose the higher end. This calculator uses 10% by default.

What density should I use?

Normal-weight concrete is approximately 145–155 lb/ft³; 150 lb/ft³ is a conservative default. Adjust downward for lightweight mixes or upward for heavy aggregates. For specification-backed values consult technical resources from agencies or material suppliers.

Is this sufficient for ordering ready-mix?

This provides a planning estimate. Add the recommended overage and confirm with your supplier (they may require rounding or minimum truck quantities). For final ordering, share plans and site constraints with the ready-mix provider.

Can the calculator handle curved or spiral stairs?

No. This tool is for straight flights approximated as a triangular prism. For curved, spiral, or multi-flight stairs, perform a more detailed breakdown by segment or consult a structural engineer.

Are safety and regulatory considerations included?

This calculator estimates material quantities only. Follow OSHA and local building codes for formwork, access, reinforcement, and worker safety. See the cited regulatory resources for guidance on safe handling and construction practices.

Sources & citations

NIST — Metric and SI Units (reference for unit consistency) — https://www.nist.gov/pml/weights-and-measures/metric-si-units
OSHA — Construction (regulatory guidance for concrete work and site safety) — https://www.osha.gov/construction
MIT OpenCourseWare — Materials / Civil engineering resources (material properties reference) — https://ocw.mit.edu
Federal Highway Administration — Concrete Pavement and Materials resources — https://www.fhwa.dot.gov/pavement
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

External guidance

Versioning & Change Control

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

Record ID: a0d413bf95d1

What changed (latest)

v1.0.0 • 2025-11-25 • 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 25, 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 • 2025-11-25 • 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: 01fdc7224173