How ConcreteQty calculates your order

1. Normalize the measurements

US measurements are converted to feet; metric measurements are converted to meters and then to a common internal volume. Changing the displayed unit does not change the physical size stored by the calculator.

2. Calculate the geometric volume

Each section uses its actual geometry: rectangular prism, cylinder, or the sum of non-overlapping sections. Openings and post displacement are subtracted only when those optional measurements are entered.

3. Apply waste

The default allowance is 10%. It is shown as a separate addition and can be changed. ConcreteQty never folds waste silently into the measured volume.

4. Round for purchasing

The quantity with waste is rounded upward to the selected supplier increment. The default is 0.25 yd³ for US units and 0.10 m³ for metric units.

5. Count bags

Bag counts divide volume with waste by published product yield and always round up to a whole bag.

6. Estimate weight and cost

The default density is 145 lb/ft³. Cost calculations convert entered currency values to integer cents before multiplication and tax, then display dollars only after rounding.

Limits

ConcreteQty calculates quantity and entered costs. It does not choose thickness, strength, reinforcement, footing depth, frost protection, or any structural dimension.

Change history

September 22, 2026: initial public calculation method, manufacturer bag yields, explicit waste and supplier rounding, measurement plausibility checks, and reversible US/Metric conversion.