Excavator Bucket Capacity Is Often Measured In
Excavator bucket capacity is primarily measured using two standardized methods defined by the Society of Automotive Engineers (SAE) and CECE (Committee for European Construction Equipment).
The measurement units used are typically cubic meters ($m^3$) or cubic yards ($yd^3$).
1. Heaped Capacity
This is the most common rating provided by manufacturers. It measures the total volume of the bucket plus the additional material piled on top at a specific angle of repose (usually 2:1 for SAE standards). This represents a "full" bucket as seen during actual operation.
2. Struck Capacity
This measures the internal volume of the bucket as if it were struck off perfectly level with the side plates and the cutting edge. It does not account for any material heaped above the top of the bucket.
Factors Influencing Actual Capacity
While the plate rating gives a theoretical volume, the fill factor determines how much material you actually move:
Material Density: Heavy, wet clay or rock may prevent a full "heaped" load compared to loose topsoil.
Bucket Shape: Wide, shallow buckets (ditching buckets) have different fill characteristics than deep, narrow trenching buckets.
Fill Factor Percentages: * Loose Earth: 100% – 110%
Rock/Blasted Shale: 60% – 75%
Sticky Clay: 80% – 90%
Calculation Formula
For technical estimations, the payload is often calculated as:
