Concrete Triangle Calculator: Yards & Bags

Concrete Triangle Calculator

Calculate triangular concrete area, volume, cubic yards, full bags, weight, truck loads and cost. Choose the geometry you actually measured and enter the mixed yield printed on the bag.

Measurement system

Triangle measurements

Identical triangles

Triangle dimensions

Base (ft)

Perpendicular height (ft)

Base and perpendicular height determine area, but not the other two side lengths; form perimeter will be unavailable in this mode.

Thickness

Thickness model

Thickness (in)

The average of two depths is exact only when thickness changes linearly across the triangular plan. Use measured sections for irregular excavation.

Ordering assumptions

Extra material (%)

Mixed yield per bag (ft³)Use the product label; do not infer yield from bag weight.

Concrete density (lb/ft³)

Price per bag

Bulk price per yd³

Truck capacity (yd³)

Currency symbol

Triangular concrete estimate

Total plan area—

Average thickness—

Geometric volume—

Order volume with extra—

Full bags to buy—

Purchased volume—

Estimated weight—

Form perimeter—

Truck loads—

Bag cost—

Bulk-volume cost—

Bag surplus—

—

Triangle formulas used

For a measured base and perpendicular height, area is base × height ÷ 2. A right triangle uses its two perpendicular legs, with the third side calculated by the Pythagorean theorem. When all three sides are known, the calculator uses Heron’s formula after checking that the sides can form a triangle.

Concrete volume equals triangular area multiplied by average thickness and the number of identical placements. The order volume adds the selected allowance. Bags are always rounded up to a whole package using the mixed yield you enter.

Material estimate only: this calculator does not choose slab thickness, reinforcement, subbase, joints, drainage, slope or concrete strength. Confirm those design decisions and local requirements separately.

Checked example

A triangle with a 12 ft base, 8 ft perpendicular height and 4 in thickness has 48 ft² of area and 16 ft³ of concrete. With 10% extra, order 17.6 ft³ or 0.652 yd³. At 0.60 ft³ of mixed yield per bag, round 29.33 up to 30 full bags.

Choosing the correct measurement mode

Mode	Required measurements	What it can calculate
Base and perpendicular height	One base and the shortest 90° distance to the opposite corner	Area and volume; perimeter is not uniquely determined
Two perpendicular legs	The two sides that meet at 90°	Area, hypotenuse, perimeter and volume
Three sides	All three edge lengths	Area by Heron’s formula, perimeter and volume

Limits and practical checks

Three-side mode rejects measurements that fail the triangle inequality.
Two-depth mode uses their arithmetic average and assumes thickness changes linearly. Split irregular pours into measured sections.
Form perimeter excludes stakes, overlaps, bracing and shared edges between adjacent placements.
Bag yield must come from the actual product label. Bag weight alone does not determine mixed volume.
Truck loads are capacity divisions rounded up; supplier minimums, partial-load fees and legal payload limits are separate.
Weight excludes reinforcement, forms, base material and embedded items.

Concrete Triangle Calculator: Yards, Bags and Cost