Concrete Triangle Calculator

Updated 2026-05-17

For a 12 ft by 10 ft triangular area at 4 inches thick, the planning estimate is 0.81 cubic yards.

Quick estimate: 0.81 cubic yards for 12 ft base by 10 ft height triangle, 4 in thick, with 10% waste.

How much concrete for a triangular area?

Use triangle area, not rectangle area. Multiply the base by the perpendicular height, divide by 2, multiply by slab thickness in feet, then divide by 27 to convert cubic feet into cubic yards.

Measure perpendicular height

The height input should be the perpendicular distance from the base to the opposite corner, not the sloped side length. For a driveway flare, patio corner, or angled walkway section, sketch the triangle before measuring.

Add triangles to other sections

Most projects are not one perfect triangle. Calculate rectangles, circles, and triangle sections separately, then add the concrete volumes before ordering.

Before you calculate

  • Measure the triangle base and perpendicular height in feet.
  • Enter slab thickness in inches and estimate curved or irregular edges separately.
  • Split complex patios, driveway flares, or corner sections into triangles and rectangles before adding totals.

Common mistakes

  • Using the sloped edge as triangle height instead of the perpendicular height.
  • Treating arcs, curves, or tapered thickness as a perfect triangle.
  • Forgetting separate rectangles, forms, reinforcement, base prep, and finishing.

Formula

cubic yards = ((base * height / 2) * (thickness / 12) / 27) * (1 + wastePercent / 100)

Assumptions

  • Defaults represent a triangular concrete pour.
  • The formula uses triangle area: base times height divided by 2.
  • Curves, arcs, varying thickness, reinforcement, and form waste should be estimated separately.

Example

Estimated concrete needed: 0.81 cubic yards

How to use this triangle concrete calculator

  1. Sketch the triangular section and measure the base in feet.
  2. Measure the perpendicular height from the base to the opposite point; do not use the sloped side as height.
  3. Enter concrete thickness in inches and keep waste visible for form variation, uneven base, and ordering variance.
  4. Calculate rectangles, circles, and other triangle sections separately, then add the volumes before ordering.
  5. Use the result as a material quantity estimate; forms, reinforcement, joints, finishing, and local requirements remain separate.

Before you buy materials

  • Use the result as a concrete quantity checkpoint before combining it with other sections.
  • Round up by supplier rules or bag yield after all project sections are added.

FAQ

What is the example concrete triangle cubic-yard result?

Use triangle base, triangle height, thickness, waste, then calculate the planning result. In the default example, the result is 0.81 cubic yards.

How do I calculate concrete for a triangle?

Use cubic yards = ((base x height / 2) x (thickness / 12)) / 27, then add waste if needed.

What is the example result on this page?

The example uses 12 ft base, 10 ft height, 4 in thickness, and waste to estimate 0.81 cubic yards.

Should I use the sloped side as triangle height?

No. Use the perpendicular height from the base to the opposite point. The sloped side is not the same measurement.

Can I use this for a curved slab?

Only as an approximation if the section is close to triangular. Curves and arcs should be broken into better-fitting shapes or measured separately.

Related calculators

This calculator is for planning estimates only. Verify final quantities with product labels, project conditions, and a qualified professional when accuracy matters.