Concrete Triangle Calculator
Calculate volume, cubic yards, and bags needed for triangular slabs.
Length of the bottom side
Perpendicular height from base
Recommended: 5-10%
Total Volume (Cubic Yards):
0.00
Total Volume (Cubic Feet):
0.00
Area Covered:
0.00 sq ft
Estimated Material Cost:
$0.00
Pre-Mix Bags Required (Estimated):
80lb Bags (Quikrete/Sakrete):
0
60lb Bags:
0
How to Calculate Concrete for a Triangle
Calculating the concrete requirements for triangular shapes—such as corner patios, garden wedges, or structural supports—requires a slightly different geometric approach than standard rectangular slabs. Accurate calculation helps you order the correct amount of ready-mix or purchase the right number of bags, preventing expensive waste or mid-project shortages.
The Formula:
1. Area (sq ft) = (Base × Height) ÷ 2
2. Volume (cu ft) = Area × (Thickness in inches ÷ 12)
3. Cubic Yards = Volume (cu ft) ÷ 27
1. Area (sq ft) = (Base × Height) ÷ 2
2. Volume (cu ft) = Area × (Thickness in inches ÷ 12)
3. Cubic Yards = Volume (cu ft) ÷ 27
Step-by-Step Calculation Guide
Follow these steps to determine your concrete volume manually:
- Measure the Base and Height: Identify the longest straight side as your base. Measure the perpendicular distance from this base to the opposite corner (the height). Ensure these measurements are in feet.
- Determine Thickness: Most residential slabs (patios, walkways) are 4 inches thick. Driveways typically require 5 to 6 inches.
- Calculate Area: Multiply the base by the height, then divide by two. For example, a triangle with a 10ft base and 10ft height has an area of 50 sq ft.
- Convert to Volume: Multiply your area by the thickness in feet. If your slab is 4 inches thick, divide 4 by 12 to get 0.33 feet. 50 sq ft × 0.33 ft = 16.5 cubic feet.
- Convert to Yards: Concrete trucks deliver by the cubic yard. Divide your cubic feet result by 27.
Why Add a Waste Factor?
In the calculator above, we include a default "Waste/Margin" field. Concrete projects rarely go perfectly according to plan. You should typically add 5% to 10% extra material to account for:
- Uneven subgrade or excavation (the ground is rarely perfectly flat).
- Spillage during the pour.
- Concrete remaining inside the mixer or pump.
- Formwork settling or bowing under weight.
Bags vs. Ready-Mix Truck
When should you buy bags, and when should you order a truck?
- Use Bags (60lb/80lb): Best for projects requiring less than 1 cubic yard. Mixing by hand or with a small rental mixer is labor-intensive but cost-effective for small corner fills or deck footings.
- Order a Truck: If your project exceeds 1 to 1.5 cubic yards, ordering ready-mix is usually more efficient. Note that many suppliers have a "short load" fee for orders under 3-4 yards.
Common Triangle Types in Construction
While the formula (Base × Height) / 2 works for all triangles, ensure you are measuring the height perpendicularly (at a 90-degree angle) from the base. For right-angled triangles (common in room corners), the two sides touching the 90-degree corner can serve as the Base and Height directly.